Veeco 004-210-000 Instruction Manual

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MultiMode SPM Instruction Manual

NanoScope Software Version 5

Document Revision History: MultiMode SPM Instruction Manual

Revision

Date

3-09-04

4.31ce "A"

27OCT97

4.22ce

14FEB97

4.22

15JUL96

004-210-000

004-210-100

Section(s) Affected

All.

Chapters 3, 5 and 8

TOC, TOW, Chapters 2, 5, 7, 11, 12, 13, 15

and Index

Released

Reference

Approval

N/A

C. Kowalski

168, 185,

189

139

Table of Contents

Chapters

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Summary of Contents for Veeco 004-210-000

Page 1 MultiMode SPM Instruction Manual NanoScope Software Version 5 004-210-000 004-210-100 Copyright © [1996, 1997, 2004] Veeco Instruments Inc. All rights reserved. Document Revision History: MultiMode SPM Instruction Manual Revision Date Section(s) Affected Reference Approval 3-09-04 All. C. Kowalski 4.31ce “A”...
Page 2 Copyright: Copyright © 2004 Veeco Instruments Inc. All rights reserved. Trademark Acknowledgments: The following are registered trademarks of Veeco Instruments Inc. All other trademarks are the property of their respective owners.
Page 3: Table Of Contents
Table of Contents Chapter 1 Introduction to the Digital Instruments MultiMode SPM 1 1.1 Introduction ..........2 1.2 Safety .
Page 4 2.5 Review of TappingMode AFM ....... . 43 2.5.1 General Operating Concepts ........43 2.5.2 Optimizing the TappingMode AFM Signal after Engagement .
Page 5 6.4 Beyond the Basics of AFM Operation ......98 6.4.1 Cantilever Selection ..........98 6.5 Optimization of Scanning Parameters .
Page 6 8.4 Troubleshooting Tips........138 8.4.1 Cantilever Tune Plot Looks Poor: Loose Probetip .
Page 7 10.2.4 Understanding the Color Scale ....... . . 171 10.2.5 Using TMR Voltage to Measure Friction ......172 10.2.6 Enhancing the LFM Data by Subtracting Two Images .
Page 8 12.5 Use of LiftMode with TappingMode ......222 12.5.1 Main Drive Amplitude and Frequency selection....222 12.5.2 Setpoint Selection .
Page 9 Chapter 15 Calibration, Maintenance, Troubleshooting and Warranty 271 15.1 SPM Calibration Overview ....... . . 275 15.1.1 Theory Behind Calibration .
Page 10 15.11.3 Head does not engage ........314 15.11.4 Head engages immediately .
Page 11 Rev. B MultiMode SPM Instruction Manual 11/(12 Blank)
Page 13 List of Figures Chapter 1 Introduction to the Digital Instruments MultiMode SPM ..1 Figure 1.1a MultiMode SPM System Components .....3 Figure 1.2a Safety Symbols Key .
Page 14 List of Figures Chapter 4 Cantilever Preparation ........57 Figure 4.1a Silicon Cantilever Substrates in Wafer.
Page 15 List of Figures Chapter 7 TappingMode AFM........103 Figure 7.1a Tapping Cantilever in Free Air .
Page 16 List of Figures Figure 9.5c STM current image of layered crystal a-RuCl3. Scan size = 4.48nm, Itun = 1.5pA, Vbias = 42mV..161 Figure 9.5d STM height image of alkanethiol layer on Au (111) substrate. Scan size = 178.5nm, Itun = 2pA, Vbias = 1V. (Courtesy of Dr. I.
Page 17 List of Figures Chapter 13 Magnetic Force (MFM) Imaging ......225 Figure 13.1a MFM LiftMode principles ......226 Figure 13.1b Basic Extender for NanoScope III, IIIa and Quadrex Extender for NanoScope IIIa Controllers (required for MFM phase detection and frequency modulation) .
Page 18 Figure 15.1b Effect of Nonlinearity and Hysteresis ....278 Figure 15.1c Veeco Silicon Calibration Reference ....280 Figure 15.3a Non-Orthogonal and Corrected, Orthogonal Image .
Page 19 List of Figures Figure 15.12b Rings During High Frequency Operation ....321 Figure 15.12c Dull or Dirty Tip ........322 Figure 15.12d Double or Multiple Tips .
Page 21: Introduction To The Digital Instruments Multimode Spm
Chapter 1 Introduction to the Digital Instruments MultiMode SPM The following sections are covered in this chapter: • Introduction: Section 1.1 • Safety: Section 1.2 • Six Rules of Safety: Section 1.2.1 • Safety Requirements: Section 1.2.2 • Safety Precautions: Section 1.2.3 •...
Page 22: Introduction
The MM-SPM is designed around a stationary probe. That is, samples are scanned back and forth beneath the probe. (This is opposite to other Veeco designs—e.g., Dimension Series SPMs—in which mounted samples are stationary while the probe scans back and forth above them.) Typically, samples are ﬁxed to round 1.5cm metal disks (“pucks”), then magnetically attached to the top of...
Page 23: Figure 1.1A Multimode Spm System Components
Introduction to the Digital Instruments MultiMode SPM Introduction Figure 1.1a MultiMode SPM System Components Computer Control monitor Display monitor NanoScope Controller Mouse Keyboard MultiMode SPM Rev. B MultiMode SPM Installation Manual...
Page 24: Safety
Introduction to the Digital Instruments MultiMode SPM Safety Safety 1.2.1 Six Rules of Safety Here is a summary of precautions to follow during your learning phase. If you follow the rules below, the MM-SPM can come to little harm and you may feel free to experiment boldly. Read the manuals! Even if you have prior experience with the MM-SPM, be sure to read Chapter 1...
Page 25: Safety Requirements
Introduction to the Digital Instruments MultiMode SPM Safety Check all connections before hardwiring external equipment External equipment which is hard-wired into the MM-SPM, such as for EFM and ECSTM imaging, requires special cautions. To prevent damage to your microscope, always check connections carefully against documentation before energizing the system.
Page 26: Safety Precautions
Introduction to the Digital Instruments MultiMode SPM Safety 1.2.3 Safety Precautions Because the MultiMode SPM features independently motorized components, it is crucial that operators become familiar with precautions to avoid injury to themselves and/or damage to samples. This section of the manual should be read by ALL persons working with or around the system.
Page 27 Introduction to the Digital Instruments MultiMode SPM Safety CAUTION: Please contact Veeco before attempting to move the MultiMode SPM system. ATTENTION: Il est impératif de contacter Veeco avant de déplacer le MultiMode SPM. VORSICHT: Bitte kontaktieren Sie Veeco bevor Sie das MultiMode SPM System transportieren. WARNING: Voltages supplied to and within certain areas of the system are potentially dangerous and can cause injury to personnel.
Page 28 Introduction to the Digital Instruments MultiMode SPM Safety WARNING: The MultiMode SPM contains a diode laser with an output of less than 1.0mW at 670nm. AVERTISSEMENT:Le microscope “MultiMode SPM” est équipé d’une diode laser dont la puissance de sortie est inférieure à 1mW à 670nm. WARNUNG: Das MultiMode SPM ist mit einem Halbleiterlaser ausgerüstet, dessen Ausgangsleistung kleiner ist als 1.0mW bei 670nm.
Page 29 Introduction to the Digital Instruments MultiMode SPM Safety WARNING: The MultiMode SPM uses a halogen lamp to illuminate samples. Exposure to non-ionizing radiation from this lamp is well within the current exposure guidelines published by the American Conference of Governmental Industrial Hygienists (ACGIH). Typical IR exposure to the user from the sample illuminator is less than 3 mW/cm .
Page 30 Introduction to the Digital Instruments MultiMode SPM Safety Microscope To avoid operator injury and equipment damage, observe the following cautions regarding the MultiMode microscope. CAUTION: If you use the equipment in a manner not specified by the manufacturer, you can impair the protection provided by the instrument.
Page 31 Introduction to the Digital Instruments MultiMode SPM Safety WARNING: Do not attempt repairs on electrical components. If it is necessary to enter the electrical chassis for any reason (e.g., to replace a computer card), power-down the entire system and disconnect it from its power source.
Page 32 Introduction to the Digital Instruments MultiMode SPM Safety Sample Safeguards CAUTION: Do not change samples in the middle of operation. Verify that the stage is clear of tools, objects, and debris at all times. Use alcohol wipes periodically to keep the stage clean of dust. Dispose of wipes in an appropriately labelled solvent-contaminated waste container.
Page 33: Microscope Specifications
ECSTM, STM and TappingMode. A complete range of Atomic Force Microscopy (AFM) and Scanning Tunneling Microscopy (STM) techniques is available with the MultiMode SPM. Some of these techniques are available only through Veeco. • Contact AFM—Measures topography by sliding the probe’s tip across the sample surface.
Page 34 AFM and STM. See the Command Reference Manual and Support Note 225. Most of these imaging techniques are discussed in this manual. If you do not ﬁnd sufﬁcient information here, refer to Veeco web site (http://www.veeco.com) to order the necessary support notes or obtain technical support.
Page 35: Controller Electronics And Auxiliary Channels
In addition, there are two ±10V analog-to-digital converters (ADCs) having 14-bit resolution and software-selectable ﬁlters. One ADC has four-way mutliplexing. All Veeco SPMs may be attached to an optional Signal Access Module (SAM), which provides direct access (via BNC connectors) to all input and output signals between the controller and the microscope.
Page 36 Introduction to the Digital Instruments MultiMode SPM Microscope Speciﬁcations MultiMode SPM Installation Manual Rev. B...
Page 37: Spm Fundamentals For The Multimode
Chapter 2 SPM Fundamentals for the MultiMode The following sections are covered in this chapter: • Hardware: Section 2.1 • MultiMode SPM: Section 2.1.1 • SPM Head: Section 2.1.2 • Scanners: Section 2.1.3 • Tipholders: Section 2.1.4 • Probes: Section 2.1.5 •...
Page 38: Hardware
SPM Fundamentals for the MultiMode Hardware • Reexamining the Control Loop: Section 2.4.1 • General Description of Main Menu Items: Section 2.4.2 • User Example: Section 2.4.3 • Review of General Operating Concepts: Section 2.4.4 • Review of TappingMode AFM: Section 2.5 •...
Page 39: Multimode Spm
SPM Fundamentals for the MultiMode Hardware 2.1.1 MultiMode SPM The heart of the system is the SPM itself, shown below (see Figure 2.1b) Figure 2.1b MultiMode SPM Photodiode adjustment knob Laser adjustment knobs SPM tip Head Tipholder X-Y head translator Sample Retaining springs Scanner...
Page 40: Spm Head
SPM Fundamentals for the MultiMode Hardware 2.1.2 SPM Head Figure 2.1c below shows a MM-SPM head with various adjustment knobs. The head and attached X-Y stage are kinematically mated to the scanner via three contact points. A pair of retaining springs hold down the head, allowing it to be raised and lowered using adjustment screws threaded through the scanner body.
Page 41: Scanners
SPM Fundamentals for the MultiMode Hardware Figure 2.1d Quad Photodetector Arrangement Laser Photodetector segments Photodetector Mirror Cantilever 2.1.3 Scanners Figure 2.1e below shows the various, interchangeable scanners. The maximum scan size and resolution of images depend upon the choice of scanner (see chart). Longer scanners, e.g., type “J,” yield larger scan sizes;...
Page 42 SPM Fundamentals for the MultiMode Hardware Because each scanner exhibits its own unique piezo properties, each has its own parameter ﬁle. When scanners are changed, the parameter ﬁle for the new scanner is changed along with it, ensuring maximum accuracy at any scan size. Loading new parameter ﬁles requires only a few seconds.
Page 43: Figure 2.1G Voltages Applied To The X- And Y-Axes Produce A Raster Scan Pattern
SPM Fundamentals for the MultiMode Hardware AC voltages applied to the scanner crystal X-Y axes produce a raster-type scan motion as represented in Figure 2.1g. The horizontal axis presented on the display monitor is referred to as the “fast axis” (in this example, the X-axis, although either axis may be designated as the “fast axis.”) and scans at a Scan rate entered by the user.
Page 44: Tipholders
Veeco ou son représentant légal pour veriﬁcation. VORSICHT: Einige ältere Ausführungen des AFM-Spitzenhalters können einen Kurzschluß verursachen falls sie mit einem MultiMode-AFM verwendet werden. Bitte wenden Sie sich im Zweifelsfall an Veeco bzw. an die für Sie zuständige Veeco-Vertretung. MultiMode SPM Instruction Manual Rev. B...
Page 45: Probes
SPM Fundamentals for the MultiMode Hardware 2.1.5 Probes Probes come in a variety of sizes, shapes and materials and are chosen according to the chosen type of imaging. Wire Probes STM probes usually consist of wire, cut and/or etched to produce atomically sharp tips at one end. Usually these are made from tungsten or platinum-iridium alloy wires.
Page 46: Figure 2.1J Two Types Of Cantilevered Probes
TappingMode, although they are not optimal for this purpose. Cantilevered Probes—TappingMode Veeco’s answer to minimizing contact AFM forces is TappingMode, a proprietary form of AFM. In this instance, a stiff crystal silicon probe is oscillated to its resonant frequency. Because the tip describes a high-frequency (e.g., 100-plus kHz), oscillating arc, it possesses sufﬁcient energy to...
Page 47 NanoScope III with an Basic Extender Module attached, or a NanoScope IV Controller. For more information regarding this attachment, contact Veeco. Specialized Probes As the ﬁeld of SPM continues its explosive growth, new probes are constantly introduced. Here are a few examples of specialized probes: •...
Page 48: Control Mechanisms And Feedback
SPM Fundamentals for the MultiMode Control Mechanisms and Feedback Control Mechanisms and Feedback To produce quality images, the SPM must be capable of controlling the tip-sample interaction with great precision. This is accomplished with the use of an electronic feedback loop, which safeguards the tip and sample by keeping forces between them at a user-speciﬁed Setpoint level.
Page 49: Figure 2.2B Early Contact Afm Which Allowed Imaging Non-Conductive Samples
SPM Fundamentals for the MultiMode Control Mechanisms and Feedback an electronic image. The main disadvantage of this method was difﬁculty in aligning the contacting tip’s cantilever and the STM tip directly above it. Figure 2.2b Early Contact AFM which allowed Imaging Non-conductive Samples Flexible cantilever STM tip Sample...
Page 50: Feedback Gains
SPM Fundamentals for the MultiMode Feedback Gains Feedback Gains The feedback system used to control tip-sample interactions and render images must be optimized for each new sample. This is accomplished by adjusting various gains in the SPM’s feedback circuit. This section discusses gains and how they are used to obtain images. 2.3.1 Proportional and Integral Gain—An Analogy To better understand gains and how they control SPM probes, consider the analogy of a hot air balloon carrying three balloonists.
Page 51: Proportional Gain
SPM Fundamentals for the MultiMode Feedback Gains 2.3.2 Proportional Gain Proportional gain means that something is done proportionally in response to something else. In the case of our ﬁrst balloonist, Peter, this means producing hot air in proportion to the balloon’s altitude above the terrain: where the terrain rises sharply, Peter uses large amounts of gas to lift the balloon;...
Page 52: Integral Gain
SPM Fundamentals for the MultiMode Feedback Gains 2.3.3 Integral Gain Integral gain is used to correct the cumulative error between a system and its target state. In the case of the balloon, it is not enough to use only proportional gain. As we have seen, the balloon will maintain a constant error around the setpoint altitude if it relies on proportional gain alone.
Page 53: Setpoint
SPM Fundamentals for the MultiMode Feedback Gains 2.3.6 Setpoint In our ballooning example, “setpoint” referred to the target altitude to be maintained. In scanning probe microscopy, “setpoint” refers to how much tip-sample force is maintained. There are two ways of deﬁning setpoint, depending upon whether one is referring to contact AFM or TappingMode.
Page 54: More About Feedback And Images
NanoScope to render images. 2.3.8 More about Feedback and Images Veeco’s unique digital signal feedback architecture is described in numerous patents ﬁled with the US Patent Ofﬁce. In summary, the basic feedback processes may be broken down as follows: LookAhead Gain In the example above, having a record of previous ﬂights over terrain enabled three balloonists to...
Page 55 SPM Fundamentals for the MultiMode Feedback Gains a similar trace of an irregular, random surface would reveal that each scan line bears little resemblance to its adjacent line. The entire purpose of LookAhead gain is to take full advantage of regular features by using every line to anticipate the next one.
Page 56: What Data Type Of Image
Integral or LookAhead gain values of 2.0. 2.3.9 What Data Type of Image? SPM technology at Veeco has rapidly grown beyond its scanning tunneling roots to encompass numerous types of microscopy. This includes: ECSTM, contact AFM, ECAFM, TappingMode in air, TappingMode in ﬂuids, amplitude and phase magnetic force microscopy (MFM), surface...
Page 57: Control Parameters And Feedback
SPM Fundamentals for the MultiMode Control Parameters and Feedback To better understand what is being viewed when selecting different Data types, consider the diagram below: height Signal out (to Z piezo) Feedback Controller Signal in (Inaux) Signal in (In0) Microscope deflection, amplitude, current auxiliary: phase, frequency, deflection during TappingMode, friction.
Page 58: General Description Of Main Menu Items
SPM Fundamentals for the MultiMode Control Parameters and Feedback comparator circuit through an analog-to-digital (A/D) converter. It is programmed to keep the two inputs of the comparator circuit equal (0V). An output voltage generated by the computer continuously moves the piezoelectric transducer in the Z direction to correct for differences read into the A/D converter.
Page 59: User Example
SPM Fundamentals for the MultiMode Control Parameters and Feedback computer to think that the SPM output is further away from the setpoint reference than it really is. The computer essentially overcompensates for this by sending a larger voltage to the Z piezo than is truly needed.
Page 60 SPM Fundamentals for the MultiMode Control Parameters and Feedback 3. The Vertical Deflection (A-B) voltage differential is sensed by the feedback electronics, causing a dropped voltage to the Z piezo crystal—the piezo retracts. As the Z piezo retracts, the cantilever recenters the laser beam onto the photodiode array (A = B). 4.
Page 61: Figure 2.4A Contact Afm Concepts (Steps 1-5 Exaggerated.)
Vertical Deﬂection (A-B) voltage about 2-3V more negative than the Setpoint voltage. Veeco recommends starting with the Setpoint voltage set to 0V and the Vertical Deﬂection (A-B) set to -2V. The reason for this is that 0V is the middle of the control range. The Rev.
Page 62 SPM Fundamentals for the MultiMode Control Parameters and Feedback indication of a good engagement is a distinct jump of about 1V from the Vertical Deﬂection (A-B) voltage to the Setpoint voltage. The displayed image is an average of the corrections made to Z in a given display period (number of samples menu item).
Page 63: Review Of Tappingmode Afm
SPM Fundamentals for the MultiMode Review of TappingMode AFM Review of TappingMode AFM 2.5.1 General Operating Concepts One advantage of TappingMode AFM is an absence of frictional forces which exert torque on the cantilever. Unlike traditional contact AFM, the feedback loop keeps a vibrating cantilever at a constant amplitude, rather than keeping a cantilever at a constant deﬂection.
Page 64: Figure 2.5A Tappingmode Afm Concepts
SPM Fundamentals for the MultiMode Review of TappingMode AFM Figure 2.5a TappingMode AFM Concepts Photodiode Array Photodiode “B” Mirror Laser Photodiode “A” Laser beam Reflected Laser Beam Oscillating tip Sample Reflected A-B (Vertical Deflection) Laser Beam Voltage Z piezo Converter O Volts Scanner Tube...
Page 65: Optimizing The Tappingmode Afm Signal After Engagement
SPM Fundamentals for the MultiMode Review of TappingMode AFM 2.5.2 Optimizing the TappingMode AFM Signal after Engagement The ﬁgures on the bottom of Figure 2.5a show the relationship between the RMS and the setpoint voltages. There are some basic rules to remember: 1.
Page 66: Terms And Abbreviations
SPM Fundamentals for the MultiMode Terms and Abbreviations Terms and Abbreviations This section contains a brief list of terms and abbreviations to assist the reader. Other terms and abbreviations are referenced in the Index at the back of this manual. AFM —Atomic force microscopy;...
Page 67 TappingMode—Proprietary mode of SPM exclusive to Veeco which utilizes an oscillating probe to obtain nanometric images. Advantages include negligible surface impacts, high resolution and sensing of magnetic, electric and chemical forces.
Page 69: Setup & Installation
Chapter 3 Setup & Installation The following sections describe the setup and installation of your MultiMode microscope: • Installing the MultiMode SPM: Section 3.1 • Component List: Section 3.2 • Unpack The System: Section 3.2.1 • Vibration Isolation: Section 3.2.2 •...
Page 70: Figure 3.2A Multimode Spm Head
Setup & Installation Component List • Vibration isolation pad • Scanner calibration reference: XYZ, 10µm x 10µm, 200nm vertical (all scanners); Mica sample (“A” scanners); 1µm XY grating (“E” scanners) • Package of Contact Mode cantilevers - silicon nitride type •...
Page 71: Unpack The System
Setup & Installation Component List 3.2.1 Unpack The System The NanoScope system is normally shipped in ﬁve separate boxes. Each monitor is shipped in its own box, the computer and controller are shipped in separate boxes, and the MultiMode SPM, cables and hardware are shipped in one box (see Figure 3.2b).
Page 72: Figure 3.2C Hardware Setup
Setup & Installation Component List Figure 3.2c Hardware Setup Display monitor Control monitor NanoScope controller Computer Keyboard Mouse (Extender not shown) CAUTION: The NanoScope controller will overheat if the computer or controller ventilation holes are blocked or if the controller is exposed to heat from an outside source.
Page 73: Figure 3.2D Rear View Of Computer On Standard Multimode Systems
Setup & Installation Component List 2. Connect computer cables (monitors, keyboard, mouse and controller) as shown below (see Figure 3.2d). Figure 3.2d Rear View of Computer on Standard MultiMode Systems Power *Verify that voltage selection switch is set correctly for your voltage.
Page 74: Figure 3.2E Installing The Scanner
Setup & Installation Component List 4. The SPM is connected to the front of the controller with the 37-pin ribbon connector. Verify that the ribbon cable is securely connected; otherwise, the microscope may not engage or exhibit other problems. Note: If a Basic Extender Module is included, install it now between the SPM and controller.
Page 75: Vibration Isolation
A ready-to-use tripod isolation system is also available from Veeco (model TRVI). Experience suggests that air tables often have poor horizontal isolation. If an air table is used, it may require additional horizontal isolation for atomic- scale images.
Page 76: System Power Up
Setup & Installation Component List 3.2.3 System Power Up CAUTION: The following section is required only during installation or after servicing and should NOT be used by untrained personnel. Prepare the System for Power-up 1. Verify that the power cord is plugged into a grounded power receptacle. 2.
Page 77: Cantilever Preparation
Chapter 4 Cantilever Preparation The MultiMode microscope comes furnished with etched silicon cantilever substrates for TappingMode AFM and silicon nitride cantilevers for Contact AFM Modes. In both cases, the cantilever probes should be inspected under the microscope when being used for the ﬁrst time to get a better understanding of how the probes and substrates are connected and taken apart.
Page 78: Figure 4.1A Silicon Cantilever Substrates In Wafer
Cantilever Preparation Silicon Cantilever Substrates 3. It may be convenient to break several substrates from the wafer at one time. Extras may be safely stored in a specially prepared closable container. At the bottom of the container, place X4-grade, GEL-PAK™ adhesive strips. Place the substrates, tips facing up, on the adhesive to permit easy removal of the substrates when needed.
Page 79: Tip Shape Of Etched Silicon Probes
Cantilever Preparation Silicon Cantilever Substrates 4.1.1 Tip Shape of Etched Silicon Probes Etched silicon probes provide the highest aspect ratio and most consistent tip sharpness of the probes supplied at present. There are some subtleties in general shape that should be understood to gain the best advantage from the etched silicon tips when imaging samples with steep walls over steps of 100nm to several microns in height.
Page 80: Figure 4.1C Silicon Probe Tip Profile Artifact (Front To Back)
Cantilever Preparation Silicon Cantilever Substrates Figure 4.1c Silicon Probe Tip Proﬁle Artifact (front to back) Scan line produced using a theoretical probe tip shape on a 1 - 2 µm deep vertical wall trench Scan direction = 0 deg. ˚ 10°...
Page 81: Figure 4.1D Silicon Probe Tip Step Profile Artifact (Side-To-Side)
Cantilever Preparation Silicon Cantilever Substrates Figure 4.1d Silicon Probe Tip Step Proﬁle Artifact (side-to-side) Scan line produced using theoretical probe tip shape on a 1 - 2 µm deep vertical wall trench Scan direction = 90 deg. 73° 73° Scan Line Profile 1 - 2 µm Deep Trench Note: Any wall angle that is >...
Page 82: Figure 4.1E Silicon Probe-Common Shape Artifact
Cantilever Preparation Silicon Cantilever Substrates Figure 4.1e Silicon Probe—Common Shape Artifact 20 - 30° Due to the nature of the etching process that shapes the tip, there is often a short angled ridge near the highest point of the tip. The exact length of the ridge is variable but rarely exceeds 0.5µm in total length.
Page 83: Figure 4.1F Common Silicon Probe Profile-Resultant Scan Artifact
Cantilever Preparation Silicon Cantilever Substrates Figure 4.1f Common Silicon Probe Proﬁle—Resultant Scan Artifact Subsequent scan line produced by using the realistic probe tip shape 10° ˚ 70 - 80° 55° Scan Line Profile 1 µm - 2 µm Deep Trench Note: Any wall angle on the left wall that is >...
Page 84: Silicon Nitride Cantilever Substrates
Cantilever Preparation Silicon Nitride Cantilever Substrates Silicon Nitride Cantilever Substrates The silicon nitride cantilever substrates used in Contact Mode can be removed from the wafer with the following procedure. Note that the cantilevers are stored tip-side-up and that the silicon is very brittle.
Page 85: Figure 4.2B Substrate Break-Off
Cantilever Preparation Silicon Nitride Cantilever Substrates Figure 4.2b Substrate Break-Off Cantilever Cantilever Substrate Substrate Hold down here with Edge of Glass end of cotton swab Slide Edge of Glass Slide Grip here with wide tweezers. Rotate downward until substrate snaps off. Press Here to Break Off Saw-Cuts...
Page 86: Tip Shape Of Silicon Nitride Probes
Cantilever Preparation Silicon Nitride Cantilever Substrates 4.2.1 Tip Shape of Silicon Nitride Probes Silicon nitride probes provide low cost and durable probes suitable for Contact Mode imaging. There are some subtleties in general shape that should be understood to gain the best advantage from the silicon nitride tips when imaging samples with steps of 0.1 to several microns in height.
Page 87: Figure 4.2E Silicon Nitride Cantilevers-Sidewall Profile Effect
Cantilever Preparation Silicon Nitride Cantilever Substrates Figure 4.2e Silicon Nitride Cantilevers—Sidewall Proﬁle Effect 65.0° 45.0° 10.0° 11˚ Scanning Profile Two types of silicon nitride cantilever probes are available: standard and oxide-sharpened tip processes. The standard devices have the nitride deposited directly into the etched silicon mold pit formed by the intersecting <111>...
Page 89: Head, Probe And Sample Preparation
Chapter 5 Head, Probe and Sample Preparation This chapter provides instructions for head, probe and sample preparation for imaging with the MultiMode SPM. It describes how to remove and install the microscope head, how to change the probe tipholder, how to mount the probe, load and position samples, and a general description of how to engage and withdraw the tip.
Page 90 Head, Probe and Sample Preparation Other chapters in this manual describe how to perform speciﬁc types of imagery. The table below outlines where you will ﬁnd additional information for each type of imagery. If you are new to SPM and want to practice, we suggest you begin with contact AFM in Chapter For Speciﬁc Information Regarding: Chapter:...
Page 91 Head, Probe and Sample Preparation WARNING: During and prior to set up of the laser, it is especially important to avoid looking directly at the laser beam or at the laser spot. The laser head should never be plugged into the microscope control electronics unless the head is installed in the Z-stage mount.
Page 92: Initial Preparation For Contact Afm Imaging
Head, Probe and Sample Preparation Initial Preparation for Contact AFM Imaging Initial Preparation for Contact AFM Imaging 5.1.1 Prepare the Sample Verify that your sample will ﬁt atop the scanner tube and is less than 8mm thick. If you already have prior experience with loading samples into the MultiMode SPM system, load your sample now.
Page 93: Load The Sample
Head, Probe and Sample Preparation Initial Preparation for Contact AFM Imaging 5.1.2 Load the Sample Remove Head and Load Sample 1. If the head is not already removed, do so now by unfastening the retaining springs on either side and unplugging the head’s micro-D connector. Gently lift the head off and set aside.
Page 94: Figure 5.1C Head Is Held Securely Using Retaining Springs
Head, Probe and Sample Preparation Initial Preparation for Contact AFM Imaging Figure 5.1c Head is Held Securely Using Retaining Springs Reattach retaining springs (2) Check Head for Free Vertical Movement Verify basic function of the motorized Z-axis by toggling the Up switch on the MultiMode base (see Figure 5.1d).
Page 95: Load Probe In Tipholder
Head, Probe and Sample Preparation Initial Preparation for Contact AFM Imaging 5.1.3 Load Probe in Tipholder • Contact Mode: Install a silicon nitride probe tip in the AFM tipholder. Figure 5.1e shows the AFM tipholder. Detailed procedures for silicon nitride cantilever substrate preparation are given in Chapter 4, including a description of the procedure to break out...
Page 96: Figure 5.1F Underside Detail Of Fluid Cell
Head, Probe and Sample Preparation Initial Preparation for Contact AFM Imaging Figure 5.1f Underside Detail of Fluid Cell Probe Wire clip Lift wire clip by pressing plunger on opposite side of tipholder. Insert probe with tweezers, then release clip. Load Probe in Tipholder Refer to Figure 5.1f.
Page 97: Install The Tipholder
Head, Probe and Sample Preparation Initial Preparation for Contact AFM Imaging 5.1.4 Install the Tipholder Figure 5.1g Install Tipholder in Head without Touching the Sample Rotate clamping screw CW (rear side of head) to secure tipholder (Rear view) Clamping screw Once the tipholder is loaded with a probe (see Figure 5.1.3 above), the tipholder is placed inside the...
Page 98: Laser Alignment
Head, Probe and Sample Preparation Laser Alignment Laser Alignment This section describes two methods for aligning the laser for all modes except STM. The ﬁrst method uses an Optical Viewing Microscope (OMV). The second method is a “projection” method. In the projection method you remove the MultiMode head and shine a laser onto a piece of white paper, producing diffraction patterns.
Page 99: Method 2: The Projection Method
Head, Probe and Sample Preparation Laser Alignment Figure 5.2a Laser Alignment with Piece of Paper 4. Reposition the laser with the screws on top of the optical head, if necessary. 5.2.2 Method 2: The Projection Method CAUTION: Turn down the illuminator intensity before proceeding with laser alignment.
Page 100: Figure 5.2B Etched Silicon Tip Laser Alignment
Head, Probe and Sample Preparation Laser Alignment Etched Silicon Tips (TappingMode) 1. In this procedure, shining the laser beam on a piece of white paper serves as a guide to aligning the laser beam with the end of the cantilever. CAUTION: Use extreme caution if you choose to remove the optical head and hold it over a piece of paper.
Page 101: Figure 5.2C Silicon Nitride Laser Alignment
Head, Probe and Sample Preparation Laser Alignment 8. Verify the laser spot by placing a piece of paper in front of the photodetector (see Section 5.2.1, Step 3). If necessary, reposition the laser with the front-rear and back-left knobs. Silicon Nitride Tips (Contact Mode AFM) 1.
Page 102 Head, Probe and Sample Preparation Laser Alignment 5. If the laser is positioned between a pair of legs of one cantilever (laser spot on surface below) turn the front-right laser control knob counter-clockwise to move the laser left in the X direction until the laser spot disappears on the surface below (see Point 3 in Figure 5.2c).
Page 103: Maximize The Sum Signal
Head, Probe and Sample Preparation Laser Alignment 5.2.3 Maximize the SUM Signal This section describes what to do after the laser spot is aligned on the cantilever and assumes knowledge of how to read voltages from the meters mounted on the front of the MultiMode base. If you are unfamiliar with reading the MultiMode voltage meters, skip ahead to MultiMode SPM Voltage Meters: Section...
Page 104: Start The Microscope Program
Head, Probe and Sample Preparation Start the Microscope Program Start the Microscope Program After any necessary software installation is complete, you are ready to start the NanoScope software. 1. To start the NanoScope software, double-click the NanoScope startup icon on the computer desktop.
Page 105: Multimode Spm Voltage Meters
Head, Probe and Sample Preparation MultiMode SPM Voltage Meters 3. Select the scanner you plan to use (Edit > Scanner). Note: In the Microscope Select dialog box, you can add a new set of hardware conﬁguration parameters by clicking New or edit the parameters of the selected microscope by clicking Edit.
Page 106 Head, Probe and Sample Preparation MultiMode SPM Voltage Meters TappingMode or Contact AFM VERT Output Signal (V) -2.6 0.00 Vertical or Horizontal Difference Sum The bottom digital meter 2 reads differences in voltage between various segments of the photodetector. With the mode switch toggled to AFM & LFM, it indicates the voltage difference (C - D), that is, the left segments minus the right segments.
Page 107: Contact Afm Mode
Chapter 6 Contact AFM Mode This chapter covers procedures for operating the MultiMode SPM in Contact AFM Mode. It is assumed the operator has previously prepared a Contact Mode probe and aligned the MultiMode head per instructions provided in Chapter 5 of this manual.
Page 108: Preparation Prior To Imaging
Contact AFM Mode Preparation Prior to Imaging • Scan size and Scan rate: Section 6.5.3 • Setpoint: Section 6.5.4 • Lowpass ﬁlter: Section 6.5.5 • Highpass ﬁlter: Section 6.5.6 Preparation Prior to Imaging 6.1.1 Adjust the Detector Offsets Verify that the MultiMode head has been ﬁtted with a Contact Mode probe tip per instructions provided in Chapter 5 of this manual.
Page 109: Signal Settings
Contact AFM Mode Preparation Prior to Imaging Figure 6.1b Laser Adjustment Knobs—Top View Horizontal Adj. Laser Spot 6.1.2 Signal Settings In Contact AFM Mode, the vertical deﬂection (Vert Deﬂ.) signal is used to provide the dynamic feedback signal for surface height tracking. The horizontal deﬂection (Horiz Deﬂ.) is only used for lateral force measurements in Contact Mode LFM.
Page 110: Adjust Tip Height Above Sample Surface
Contact AFM Mode Preparation Prior to Imaging 6.1.3 Adjust tip height above sample surface Next, use the adjustment screws to adjust the tip height just above the sample surface. The magniﬁer can be used to monitor the tip while this is done. The coarse adjustment screws (if so equipped) are located in front and may be used to make gross adjustments.
Page 111: Suggested Initial Control Settings
Contact AFM Mode Suggested Initial Control Settings Suggested Initial Control Settings 6.2.1 Show All Items Before changing any parameters, you should display all of the available parameters. If you cannot view a parameter in a panel, you might need to enable this parameter. 1.
Page 112: Initial Scan Parameter Settings
Contact AFM Mode Suggested Initial Control Settings 6.2.2 Initial Scan Parameter Settings Before making changes to Scan Controls panel screen parameters, go to the Other Controls panel (Panels > Other) and verify that the Microscope Mode parameter is set to Contact. Scan Controls Panel 1.
Page 113: Figure 6.2E Channel 1 Panel For Initial Setup (Contact Mode)
Contact AFM Mode Suggested Initial Control Settings Interleave Controls Panel If it is not already present, open the Interleave Controls Panel by selecting Panels > Interleave. Verify that the Interleave mode ﬁeld is set to Disabled. (Do not attempt to set Interleave mode to Enabled at this point).
Page 114 Contact AFM Mode Suggested Initial Control Settings Feedback Controls Panel 1. Next, select Panels > Feedback. 2. Set both Integral and Proportional gain to 2.0 each and the Deflection Setpoint to 0.0V. Figure 6.2f Feedback Controls Panel Settings for Initial Setup (Contact Mode) Other Controls Panel 1.
Page 115: Initiate The Engage Command
Contact AFM Mode Initiate the Engage Command Initiate the Engage Command Select Motor > Engage (or click the Engage icon). A pre-engage check, followed by Z-stage motor sound should be observed. If for any reason the engage aborts because the SPM head is still too far away from the surface, click on the Abort button and readjust the screws to start the tip closer to the sample surface.
Page 116 Contact AFM Mode Initiate the Engage Command What is happening? The piezo is being retracted from the Z scan start position to the Z scan start-plus-Scan size position. The Z scan start point is at the left-most portion of the plot. The Z scan start-plus-Scan size point is the right-most portion of the plot.
Page 117 Contact AFM Mode Initiate the Engage Command Now adjust the Setpoint for imaging. Having the setpoint anywhere above the line where the tip is off the surface will work. The farther it is above, the more force is placed onto the sample. To adjust tip-sample force to the minimum amount, you can run in the area where the tip is actually pulling up but the liquid layer is holding the tip on the surface.
Page 118: Adjust Sensitivity (If Required)
Contact AFM Mode Beyond the Basics of AFM Operation 6.3.2 Adjust Sensitivity (if required) If imaging in Deﬂection mode instead of Height mode, adjust the detector’s Sensitivity parameter to the cantilever as described in this section. Use the mouse to draw a line parallel to the part of the plot where the tip is on the surface.
Page 119: Optimization Of Scanning Parameters
Contact AFM Mode Optimization of Scanning Parameters type silicon nitride probes which are used in some older, interferometric microscope heads; however, they may still be used. Each silicon nitride cantilever substrate includes four cantilever probes with different sizes and spring-constants. Two of the cantilevers on each substrate measure 115µm from the substrate to the apex of the triangular cantilever (these are referred to as 100µm cantilevers) while the other two cantilevers measure 193µm from the substrate to the apex of the triangular cantilever (these are referred to as 200µm cantilevers).
Page 120: Gain Settings
Contact AFM Mode Optimization of Scanning Parameters the height of the sample. Deﬂection data should be collected with low feedback gains so the piezo remains at a constant position relative to the sample. In this case, the tip and cantilever will be deﬂected by the features on the sample surface.
Page 121: Setpoint
Contact AFM Mode Optimization of Scanning Parameters 6.5.4 Setpoint The Setpoint parameter deﬁnes the desired voltage (and, therefore, the desired deﬂection of the cantilever) for the feedback loop. The setpoint voltage is constantly compared to the present photodiode cantilever deﬂection voltage to calculate the desired change in the piezo position. When the gain values are high, as they should be when the Data type is set to Height, the Z piezo position changes to keep the photodiode output signal close to the Setpoint;...
Page 123: Tappingmode Afm
Chapter 7 TappingMode AFM This chapter covers procedures for operating the MultiMode SPM using TappingMode in air. It is assumed that the operator has previously prepared a TappingMode probe tip and aligned the SPM head per instructions provided in Chapter 5 of this manual.
Page 124: Basic Principle Of Tappingmode
TappingMode AFM Basic Principle of TappingMode Basic Principle of TappingMode Figure 7.1a represents a cantilever oscillating in free air at its resonant frequency. A piezo stack excites the cantilever substrate vertically, causing the tip to bounce up and down. As the cantilever bounces vertically, the reﬂected laser beam is deﬂected in a regular pattern over a photodiode array, generating a sinusoidal electronic signal.
Page 125: Preparation Prior To Imaging
TappingMode AFM Preparation Prior to Imaging Preparation Prior to Imaging 7.2.1 Switch to TappingMode The microscope must be switched to TappingMode. Go to the Realtime > Microscope > Proﬁle and select the proﬁle TappingAFM. Toggle the selector switch on the left side of the MultiMode base to TM AFM;...
Page 126: Check Parameters
TappingMode AFM Preparation Prior to Imaging 3. Click the “minus box” in the upper left corner of the panel, and click Show all items. The panel will once again appear in normal Realtime mode. 7.2.3 Check Parameters Check that the Realtime control panel parameters are set within reasonable limits for TappingMode operation.
Page 127: Adjust Laser And Photodetector
TappingMode AFM Preparation Prior to Imaging 7.2.4 Adjust Laser and Photodetector Verify that the tipholder has been ﬁtted with a TappingMode, single crystal silicon probe and aligned per instructions provided in Chapter 5 of this manual. Photodetector voltage values are displayed on meters mounted on the front of the MultiMode base.
Page 128: Figure 7.2D Voltage Meters On The Multimode Base Reveal A Great Deal About The
TappingMode AFM Preparation Prior to Imaging Figure 7.2d Voltage meters on the MultiMode base reveal a great deal about the amplitude and alignment of the TappingMode laser signal on a tuned tip operating at its resonant frequency. Small laser signal amplitude yields low output voltage.
Page 129: Additional Preparations
TappingMode AFM Preparation Prior to Imaging 7.2.5 Additional preparations In TappingMode, the RMS amplitude representing AC voltage signal is used to provide the dynamic feedback signal for surface height tracking. The vertical deﬂection signal (displayed on the “Vertical or Horizontal Difference” meter) should be close to zero (± 1.0V) prior to running Cantilever Tune and/or attempting engagement.
Page 130: Figure 7.2E Cantilever Tune Panels
TappingMode AFM Preparation Prior to Imaging Figure 7.2e Cantilever Tune Panels The Frequency Sweep (a plot of cantilever response as a function of applied vibrational frequency) is shown on the display monitor. The two main panels, Sweep Controls and Auto Tune Controls (see Table 7.2a), allow the operator to either manually or automatically tune the cantilever.
Page 131: Figure 7.2F Sweep Control Panels For Graph Controls (Left) And Main Controls
TappingMode AFM Preparation Prior to Imaging Tuning cantilevers manually The parameter values, especially the drive frequency and the sweep width, given in the following example apply to one type of cantilever. The nominal parameter values may vary depending upon the actual cantilever used. For initial set-up, select View >...
Page 132: Setting The Drive Amplitude And Setpoint
TappingMode AFM Preparation Prior to Imaging 2. If a peak in the frequency response plot does not appear, perform the following steps: • Increase the Drive amplitude to 600mV. • Increase Sweep width to the maximum value. If the peak still has not appeared, then increase the Sweep width by ﬁrst increasing the Drive Frequency, then maximizing the Sweep width.
Page 133: Engaging The Microscope
TappingMode AFM Engaging The Microscope actual setpoint value adjusted by the user prior to engage is meaningless because the operating setpoint is determined automatically during engage by the control program. 2. Select View > Image Mode, or click the Back to Image Mode button or the Image Mode icon.
Page 134 TappingMode AFM Engaging The Microscope Figure 7.3b Suggested Other Controls Settings During TappingMode Setup 2. Move the probe to the area of interest using the X-Y translation knobs on the MultiMode head. 3. Use the meters to verify that the vertical deflection is between -1 and +1, the RMS amplitude (topmost meter) is 1-2V, and the sum voltage is greater than 1V.
Page 135: Withdrawing The Tip
TappingMode AFM Withdrawing the Tip Withdrawing the Tip Select Withdraw from the Motor menu. The SPM will stop scanning, then ascend approximately 10µm. If more clearance between tip and sample is desired, toggle the Up / Down switch on the top-right side of the MultiMode base. Never withdraw samples without carefully observing that the tip has adequate clearance during the entire sample removal sequence.
Page 136: Figure 7.5B Scope Trace With High Scan Rate
TappingMode AFM Beyond Basics with Resonating Techniques At Setpoint 1 the operating point is only slightly lower than the free vibration amplitude. This has the advantage of dissipating very little energy to the sample surface. (The drawback is that the system takes longer to recover from a given perturbation in the amplitude.) Consider the case where the tip travels off a step with a height of ∆x.
Page 137: Tuning The Cantilever Drive Frequency
TappingMode AFM Beyond Basics with Resonating Techniques Figure 7.5c Scope trace with Correct Scan Rate Trace Retrace Z Range 50.00 nm/div Scan Size - 2.50 µm/div 7.5.2 Tuning the Cantilever Drive Frequency The Drive frequency selected to oscillate the cantilever plays an important role in the performance of the microscope while in TappingMode.
Page 138: Optimization Of Scanning Parameters
TappingMode AFM Beyond Basics with Resonating Techniques 7.5.3 Optimization of Scanning Parameters Careful selection of the scan parameters is important to the successful application of the MultiMode in TappingMode. In general, the effects of the various scan parameters are the same for the TappingMode as they are for contact AFM mode.
Page 139 TappingMode AFM Beyond Basics with Resonating Techniques Scan Size, Scan Rate, and Setpoint As discussed above, the Scan size, Scan rate, and Setpoint values have dramatic effects on the data. As in contact mode, the Scan rate must be decreased as the Scan size is increased. Scan rates of 0.5-1.0Hz should be used for large scans on samples with tall features.
Page 141: Fluid Operation
Chapter 8 Fluid Operation This chapter addresses scanning probe microscope (SPM) imaging of samples in ﬂuid using a MultiMode. Refer to the following for your speciﬁc area of interest: • Introduction: Section 8.1 • General Fluid Operation: Section 8.2 • Clean Fluid Cell and O-ring: Section 8.2.1 •...
Page 142 Fluid Operation • Poor Image Quality: Section 8.4.3 • Lost Particulate Samples: Attracted to Cantilever: Section 8.4.4 • Drift in AFM Image Because O-ring Slid Across Sample Surface: Section 8.4.5 • General Notes on Sample Binding: Section 8.5 • Lysozyme on Mica—A Model Procedure for Protein Binding: Section 8.6 •...
Page 143: Introduction
ﬂuid environments, and/or the necessity to make real time observations of samples undergoing electrochemical reactions (ECAFM). In order to conduct ECAFM observations with electrical potentials, it is necessary to connect an external potentiostat unit. Contact Veeco for more information.
Page 144: Figure 8.2A Fluid Cells
Fluid Operation General Fluid Operation Figure 8.2a Fluid Cells TappingMode Fluid Cell Contact Mode Fluid Cell There are two ﬂuid cells that are commonly used for ﬂuid imaging: • Model FC is a ﬂuid cell can be used for imaging samples in ﬂuid using Contact Mode only.
Page 145: Clean Fluid Cell And O-Ring
O-ring design has an “S” shaped cross-section with thin, ﬂexible walls. This new design makes insertion of the O-ring easier, reducing the chances of leaking and minimizing imaging artifacts caused by lateral friction. Two additional ﬂuid cell designs are available from Veeco: • Contact Mode electrochemical ﬂuid cell (Model ECFC) •...
Page 146: Remove Organic Contamination From The Tip
Fluid Operation General Fluid Operation 8.2.3 Remove Organic Contamination from the Tip Contaminants on the tip may limit AFM resolution. You may use ultraviolet (UV) light to remove contaminants, as follows: 1. Place the fluid cell with installed tip face-up on a clean surface. 2.
Page 147: Sample Mounting
Fluid Operation General Fluid Operation Figure 8.2b Load Probe into Fluid Cell Probe Wire Clip Pocket Fluid Cell (Bottom) 8.2.5 Sample Mounting Secure a sample support (e.g., mica or a glass cover slip) to a magnetic stainless steel sample puck. Supports may be secured to the puck with epoxy.
Page 148: Figure 8.2C Fill The Fluid Cell With Liquid
Fluid Operation General Fluid Operation 1. Install the protective O-ring into the fluid cell. Insert the O-ring into the recessed groove in the underside of the fluid cell. The O-ring slides up into the recessed groove. 2. Install the sample or sample support in the fluid cell. 3.
Page 149 Fluid Operation General Fluid Operation Note: To minimize the risk of ﬂuid leakage, introduce ﬂuid to the ﬂuid cell under vacuum using the following technique: • Attach a piece of silicone tubing to one of the ﬂuid ports using a male Luer ﬁtting. Place the free end of the tubing into a beaker containing the buffer.
Page 150: Figure 8.2D Stainless Steel Sample Puck With Teflon Cover
Fluid Operation General Fluid Operation Figure 8.2d Stainless Steel Sample Puck with Teﬂon Cover Mica Aqueous Sample Teflon Stainless Steel Sample Puck You may load the sample on the support now, or you may inject it when the ﬂuid cell is installed inside the AFM head.
Page 151: Align The Laser
Fluid Operation General Fluid Operation Figure 8.2f Imaging a Sample Covered by a Drop of Fluid Fluid Probe Holder Meniscus Sample Puck Scanner 2. Complete the following if starting with a sample in solution: a. Incubate 30-40µl of your sample on the support mounted on the puck (the liquid should form a small dome over the support).
Page 152: Adjust The Detector Offsets And Setpoint (Contact Mode)
Fluid Operation General Fluid Operation 8.2.7 Adjust the Detector Offsets and Setpoint (Contact Mode) Adjust the detector mirror adjustment screws: • In Contact Mode (i.e., Other Controls > Microscope mode set to Contact and Feedback Controls > SPM Feedback set to Deﬂection), to achieve a vertical deﬂection signal of roughly -1.0V.
Page 153: Clean And Dry Parts When Done
Fluid Operation General Fluid Operation 2. To avoid sample damage, reduce the Deflection Setpoint as low as possible: Stop when the tip pulls off the surface and the Z Center Position on the display monitor jumps to Limit (-220V). 3. Increase the setpoint until the tip begins to touch the surface again and an image appears. •...
Page 154: Tappingmode In Fluids
Fluid Operation TappingMode in Fluids TappingMode in Fluids Operation of TappingMode in ﬂuid provides the same advantages of TappingMode in air, with the additional ability to image samples under native liquid conditions. In ﬂuid TappingMode, the probe is oscillated so that it only intermittently contacts the sample surface. This can reduce or eliminate lateral forces that can damage soft or fragile samples in Contact Mode.
Page 155: Figure 8.3A A 100Μm, Narrow-Legged, Si
Fluid Operation TappingMode in Fluids Figure 8.3a A 100µm, Narrow-legged, Si Cantilever Fluid Tune Curve • Manually adjust the Zoom in and Offset functions above the Cantilever Tune display. Note: If the expected peak does not appear in the spectrum, choose another peak, engage on the surface and disengage immediately.
Page 156: Plotting Amplitude Vs. Distance (Force Cal Curve)
Fluid Operation TappingMode in Fluids • Adjust and optimize these settings for each imaging condition and sample. Center the laser spot on the photodiode detector. • Adjust the photodiode until deﬂection is roughly zero. • The deﬂection signal can drift when the probe is ﬁrst in ﬂuid, so it is best to adjust just prior to engaging.
Page 157: Optimizing Image Quality
Fluid Operation TappingMode in Fluids Note: The slope of the Force Cal curve during probe interaction with the sample surface is deﬁned as the sensitivity of the ﬂuid TappingMode measurement. In general, higher sensitivity results in better image quality. If the sensitivity is poor, check the mounting of the sample and ﬂuid cell.
Page 158: Troubleshooting Tips
ﬂuid cell. For example, the probe may be loose in its holder. Check the clip which holds the probe in place, and verify the probe is not loose. Contact Veeco for assistance if needed.
Page 159: Lost Particulate Samples: Attracted To Cantilever
Unlike three-point supports, the vertical engage scanner allows the tip to approach samples without lateral offset, eliminating stress on the O-ring during engagement. For more detail, contact Veeco. • Lightly coating the area of the O-ring which contacts the sample surface with white petrolatum or vacuum grease allows the O-ring to slide across the surface, minimizing Rev.
Page 160 Fluid Operation Troubleshooting Tips lateral stress. This also forms a ﬂuid-tight seal between the O-ring and sample. However, some solvents (i.e., nonpolar organic solvents) may dissolve some of the lubricant into the ﬂuid. • Substitute an alternative for the O-ring: •...
Page 161: General Notes On Sample Binding
Both of these techniques are discussed separately below. Many other techniques are being developed for chemically modifying mica, glass and other substrates to bind a variety of biological samples. Contact Veeco for a bibliography of references on imaging of biological specimens.
Page 162: Lysozyme On Mica A Model Procedure For Protein Binding
Fluid Operation Lysozyme on Mica—A Model Procedure for Protein Binding Lysozyme on Mica—A Model Procedure for Protein Binding 8.6.1 Protein Binding Theory All proteins contain free amino groups that become positively charged at sufﬁciently low pH. If sufﬁcient free amino groups are located on the outside surface of the protein, then the protein will bind to a negatively charged mica surface.
Page 163 Fluid Operation Lysozyme on Mica—A Model Procedure for Protein Binding • TappingMode Fluid Cell, Model MMTFC • Cantilevers (Oxide-Sharpened Silicon Nitride tips, Model NP-S, work well) • Source of ﬁltered (0.2 µm), compressed air or dry nitrogen • UV lamp, high-intensity; Oriel Mod. 6035 pencil-style spectral calibration lamp or equivalent (optional for cantilever cleaning).
Page 164: Figure 8.6B Tappingmode Image Of Lysozyme In Buffer Solution Using Above Sample Preparation (Scan Size = 500Nm)
Fluid Operation Lysozyme on Mica—A Model Procedure for Protein Binding 9. After the fluid cell has been flushed with buffer solution, reclamp the drain line. This is important for low-noise, low drift imaging. The sample is now ready for TappingMode imaging.
Page 165: Binding Dna To Mica
DNA in situ with Atomic Force Microscopy.” Proc. Natl. Acad. Sci. USA 94, 496. Many other references regarding DNA imaging are listed in the Digital Instruments Biological Applications Bibliography; call Veeco for a copy. Rev. B MultiMode SPM Instruction Manual...
Page 166: Acknowledgments
The sample is now ready for TappingMode imaging. 8.7.3 Acknowledgments Veeco wishes to express its appreciation to the following individuals for sharing their experience to assist in preparing this section: Monika Fritz, Manfred Radmacher, Magdalena Bezanilla, Helen G. Hansma, Paul Hansma, Jason Cleveland, Jan H. Hoh, Serge Magonov, Chris Johnson, Don Hersch, Tom Kovaleski, Gouliang Yang, Jamie Vesenka, and Eric Henderson.
Page 167: Scanning Tunneling Microscopy (Stm)
Chapter 9 Scanning Tunneling Microscopy (STM) STM relies on “tunneling current” between the probe and the sample to sense the topography of the sample. The STM probe, a sharp metal tip (in the best case, atomically sharp), is positioned a few atomic diameters above a conducting sample which is electrically biased with respect to the tip.
Page 168: Stm Introduction
Scanning Tunneling Microscopy (STM) STM Introduction • Low-Current STM: Section 9.5 • Description: Section 9.5.1 • Hardware Description: Section 9.5.2 • Precautions: Section 9.5.3 • Installation: Section 9.5.4 • Operation: Section 9.5.5 • Servicing the Converter: Section 9.5.6 • Etching Tungsten Tips: Section 9.6 •...
Page 169: Stm Hardware
PtIr Probes—PtIr probes are mechanically formed and can be purchased directly from Veeco. PtIr probes seem to give better atomic resolution than tungsten, most likely due to the lower reactivity of platinum.
Page 170: Sample Surface
Scanning Tunneling Microscopy (STM) STM Introduction 9.1.3 Sample Surface Samples to be imaged with a scanning tunneling microscope must conduct electricity. In many cases nonconductive samples can be coated with a thin layer of a conductive material to facilitate imaging. The sample surface must be conductive enough to allow a few nanoamps of current to ﬂow from the bias voltage source to the area to be scanned.
Page 171: Basic Stm Operation
Scanning Tunneling Microscopy (STM) Basic STM Operation Basic STM Operation 9.2.1 System Setup This section explains how to use the NanoScope to image a conductive sample. Select the STM option in the software Select Microscope > Proﬁle > STM or Other Controls panel > Microscope mode > STM. Prepare the sample The STM bias voltage is supplied to the sample through the top of the scanner.
Page 172: Figure 9.2A Select Show All Items
Scanning Tunneling Microscopy (STM) Basic STM Operation Set Initial Scan Parameters 1. “Show All Items”: Before changing any parameters, you should display all of the available parameters. If you cannot view a parameter in a panel, you might need to enable this parameter.
Page 173: Spectroscopy With The Stm
Scanning Tunneling Microscopy (STM) Spectroscopy with the STM 2. Prior to engaging the microscope it is necessary to set the Bias voltage and Current Setpoint. A good typical Current Setpoint is 1-2nA. A good recommended Bias voltage is 20-50mv for highly conductive samples like graphite or gold. Try using Bias voltages of 100-500mv for less conductive materials.
Page 174: Operation Of Sts
Scanning Tunneling Microscopy (STM) Spectroscopy with the STM 9.3.2 Operation of STS In the following sections, the operation of the spectroscopic functions of the NanoScope III STM will be discussed. Additional information can be obtained from the Command Reference Manual. STS Plot There are several items that you should be aware of when using the NanoScope to acquire spectroscopic plots with the STS Plot commands.
Page 175: Troubleshooting For Stm
Scanning Tunneling Microscopy (STM) Troubleshooting for STM Troubleshooting for STM This section addresses errors or malfunctions encountered during the operation of the MultiMode as an STM. See Chapter 15 in this manual for additional troubleshooting tips. 9.4.1 Head and Microscope-related Problems This section deals with problems related to the scanners or the microscope.
Page 176: Low-Current Stm
Higher bias voltages are required for these types of samples. Low-Current STM The following sections provide detailed instructions for performing low-current (sub-picoamp) STM using two Veeco devices: the Low Current STM Converter for MultiMode AFM (Model #MMSTMLC), or with the Basic Extender Module (Model #MMSTMLCE). 9.5.1 Description...
Page 177: Hardware Description
Scanning Tunneling Microscopy (STM) Low-Current STM 9.5.2 Hardware Description The Low Current STM head, which allows STM measurements with I in the pA range is constructed for operation with our MultiMode and AFM bases. Low-current STM operation also requires the Picoamp Boost Box, which is installed between the control unit or extender box and the MultiMode or AFM base.
Page 178: Installation
Always disconnect the Picoamp Boost Box and Low-current STM Converter head before performing other types of imaging. 9.5.4 Installation The low-current STM converter is designed to be installed on any of the following Veeco devices: • MultiMode SPM (standard) •...
Page 179 Boost box indicates whether it was set for standard (Model MMSTMLC) or Extender (Model MMSTMLCE) at the factory. If you are not certain which base your MultiMode has, contact Veeco for guidance. 1. Turn off all power to the SPM controller. Disconnect and remove the MultiMode head.
Page 180: Operation
Scanning Tunneling Microscopy (STM) Low-Current STM Preamp Setting Current Sensitivity Setting 0.1nA/V 0.01nA/V 9.5.5 Operation The operation of the low-current STM head is typically checked in the atomic-scale imaging of graphite and the large-scale imaging of a gold-coated grating. The atomic-lattice of graphite is well resolved in the images obtained with I in the 2-20pA and V in the 20-100mV range.
Page 181 Scanning Tunneling Microscopy (STM) Low-Current STM Figure 9.5b STM current and height images of HOPG surface. Scan size = 6.0nm, I = 1.6pA, V = 29mV. bias Figure 9.5c STM current image of layered crystal α-RuCl Scan size = 4.48nm, I = 1.5pA, V = 42mV.
Page 182: Servicing The Converter
Scanning Tunneling Microscopy (STM) Low-Current STM Figure 9.5d STM height image of alkanethiol layer on Au (111) substrate. Scan size = 178.5nm, I = 2pA, V = 1V. (Courtesy of Dr. I. Tuzov, NCSU) bias Figure 9.5e Molecular-scale STM current image of alkanethiol layer on Au (111) substrate.
Page 183 Scanning Tunneling Microscopy (STM) Low-Current STM 2. Use the 0.050" allen wrench, included in the converter kit, to loosen the two retaining screws which secure the head’s cover. It is not necessary to remove the screws. Loosen these two screws. 3.
Page 184: Etching Tungsten Tips
7. Replace the metal cover on the head. Retighten retaining screws to secure. Etching Tungsten Tips You can purchase tungsten tips from Veeco or make them yourself. This section describes the process of etching tungsten tips. Materials and Equipment Required: •...
Page 185: Procedure
Scanning Tunneling Microscopy (STM) Etching Tungsten Tips 9.6.1 Procedure 1. Mix a 5% (by weight) solution of Sodium Nitrite in water. 2. Pour ≈ 40ml of the Sodium Nitrite solution into a beaker. 3. Pour ≈ 40ml of WD 40 into a beaker. 4.
Page 187: Lateral Force Mode
Lateral Force Mode Chapter 10 Lateral Force Mode The MultiMode SPM is capable of measuring frictional forces on the surfaces of samples using a special measurement known as lateral force microscopy (LFM). The name derives from the fact that cantilevers scanning laterally (perpendicular to their lengths) are torqued more as they transit high-friction sites;...
Page 188: Basic Lfm Operation
Lateral Force Mode Basic LFM Operation 10.1 Basic LFM Operation 1. Set up and run the system in Contact mode as described in Chapter 6, assigning the Channel 1 image to Data Type: Height and the Channel 2 image to Data Type: Friction. Set the Scan angle to 90.00.
Page 189: Advanced Lfm Operation
Lateral Force Mode Advanced LFM Operation 10.2 Advanced LFM Operation 10.2.1 Scan Direction The cantilever is most susceptible to frictional effects when the scan direction runs perpendicular to the major axis of the cantilever as shown in Figure 10.2a. The Scan angle parameter in the Scan Controls panel must be set to 90°...
Page 190: Tip Selection
Lateral Force Mode Advanced LFM Operation 10.2.2 Tip selection The analog-to-digital converter on the auxiliary input channel which is used for LFM data has a maximum input range of ±10V. This, and the anticipated interaction between tip and sample deﬁne the selection of the cantilever to be used for the measurement.
Page 191: Understanding The Color Scale
Lateral Force Mode Advanced LFM Operation Table 10.2a Key for LFM Example Above Trace or Level of Number Photo Diode Voltage Retrace? Movement Friction trace slightly right slight slightly positive “ severely right higher increases positive “ straightens slight returns to slightly positive “...
Page 192: Using Tmr Voltage To Measure Friction
Lateral Force Mode Advanced LFM Operation 10.2.5 Using TMR Voltage to Measure Friction The signal called TMR (Trace minus Retrace) in the scope mode display measures the voltage difference between the Trace and the Retrace scan directions. In the case of LFM data, this directly corresponds to the amount of total tip twist that occurs as the tip scans back and forth across the sample.
Page 193: Height Artifacts In The Signal
Lateral Force Mode Advanced LFM Operation 10.2.7 Height Artifacts in the Signal LFM is subject to height artifacts due to coupling with surface topography. Delay in the feedback loop causes the tip to momentarily twist as it climbs up an edge. This will be visible in the friction data if it’s severe enough.
Page 195: Force Imaging
Chapter 11 Force Imaging Force plots are used to measure tip-sample interactions and determine optimal setpoints. More recently, microscopists have begun to collect force measurements across entire surfaces to reveal new information about the sample. This area of SPM promises to open new chapters in materials science, biology and other investigative areas.
Page 196 Force Imaging • Force Calibration (TappingMode): Section 11.5 • Force Plots: Section 11.5.1 • Obtaining a Force Plot (TappingMode): Section 11.5.2 • High Contact Force: Section 11.5.3 • Tip Selection: Section 11.5.4 • Force Modulation: Section 11.6 • Introduction: Section 11.6.1 •...
Page 197: Force Plots-An Analogy
Force Imaging Force Plots–An Analogy 11.1 Force Plots–An Analogy A force plot is an observation of tip-sample interactions which yields information regarding the sample and tip. By way of analogy, suppose a materials researcher must determine how powerful two different types of magnets are. One magnet is made of iron, the other is a stronger, so-called “rare earth”...
Page 198: Force Calibration Mode
Force Imaging Force Calibration Mode First, magnet #1 is weaker, attaching to the steel plate with 7N of pulling force at 6cm, and magnet #2 is stronger, attaching at 7cm with 10N. Figure 11.1b Pulling Forces Graph Magnet #1 Magnet #2 9 10 11 Height above steel plate (cm) This oversimpliﬁed model depicts activity between SPM tips and various materials.
Page 199: Figure 11.2B Relationship Of Z Scan Start And Scan Size
Force Imaging Force Calibration Mode As a result of the applied voltage, the sample moves up and down as shown in Figure 11.2c. The Z scan start parameter sets the offset of the piezo travel, while the Ramp size parameter deﬁnes the total travel distance of the piezo.
Page 200: Example Force Plot
Force Imaging Force Calibration Mode 11.2.1 Example Force Plot Figure 11.2c Tip-Sample Interaction During a Force Plot Let’s begin with the simplest of SPM force plots: a contact AFM force plot using a silicon nitride tip. Because of the lower spring constant of silicon nitride probes, they are more sensitive to attractive and repulsive forces.
Page 201: Contact Afm Force Plots
Force Imaging Force Calibration Mode Controls panel deﬁnes the rate at which the piezo completes an extension-retraction cycle (and therefore the rate at which new curves are displayed). 11.2.2 Contact AFM Force Plots Figure 11.2d Anatomy of a Force Curve Piezo extension Piezo retraction Piezo extends;...
Page 202 Force Imaging Force Calibration Mode The cantilever’s deﬂection is plotted on the vertical axis of the graph: when the cantilever is deﬂected downward, it is plotted on the graph’s downward vertical; when the cantilever is deﬂected upward, it is plotted on the graph’s upward vertical. The graph reveals at least two very important things: •...
Page 203: Force Calibration Control Panels And Menus
Force Imaging Force Calibration Control Panels and Menus 11.3 Force Calibration Control Panels and Menus The Force Calibration Control window (see Figure 11.3a) manipulates the microscope in Force Calibration mode. The parameters control the rate, start position and amplitude of the triangle wave applied to the Z piezo.
Page 204: Main Controls (Ramp Controls)
Force Imaging Force Calibration Control Panels and Menus 11.3.1 Main Controls (Ramp Controls) Ramp Channel (Advanced Only) This parameter speciﬁes the channel you will ramp. To collect force plots, this parameter should be set to Z. For IV curves, Bias is typically selected. Ramp Size As shown in Figure...
Page 205: Main Controls Panel (Display)
Force Imaging Force Calibration Control Panels and Menus Number of Samples This parameter deﬁnes the number of data points captured during each extend and retract operation of the Z piezo during Force Calibration. This parameter does not affect the number of samples used in Image Mode.
Page 206: Channel 1, 2, 3 Panels
Force Imaging Force Calibration Control Panels and Menus 11.3.3 Channel 1, 2, 3 Panels Data Type This parameter allows you to select the type of data you want to display on the vertical axis. Data Scale This parameter sets the vertical scale in the force plot. Increasing this parameter expands the range of the display about the centerline causing more of the force curve to fall on the graph.
Page 207: Feedback Controls Panel
Force Imaging Force Calibration Control Panels and Menus 11.3.4 Feedback Controls Panel All of the parameters in the Feedback Controls panel also affect Image mode. Deﬂection Setpoint (Contact Mode) By changing the deﬂection setpoint, you can adjust the cantilever deﬂection voltage maintained by the feedback loop in Image mode.
Page 208: Scan Mode Panel (Advanced Mode Only)
Force Imaging Force Calibration Control Panels and Menus 11.3.5 Scan Mode Panel (Advanced Mode Only) Trigger Mode The Scan Mode panel allows you to use various triggers when obtaining Force Plot and Force Volume plots. The idea of triggering simple: it limits the total amount of force exerted by the tip upon the sample.
Page 209 Force Imaging Force Calibration Control Panels and Menus Trigger Threshold This parameter as well as the Trigger Direction and Trigger Mode deﬁne the level at which trigger occurs. Trigger Direction The Trigger Directions are deﬁned as follows: • Positive: Trigger occurs on positive values only (Trigger Threshold must be positive) •...
Page 210: Menu Bar Commands
Force Imaging Force Calibration Control Panels and Menus Ramp Delay This parameter sets the amount of time to wait with the piezo extended before retracting. Reverse Delay This parameter sets a delay to occur each time the piezo is retracted while continuously ramping. Auto Offset If the trigger is not achieved within a range twice the ramp size, then the retract will begin without reaching the trigger voltage.
Page 211: Force Calibration (Contact Mode Afm)
Force Imaging Force Calibration (Contact Mode AFM) Motor The Motor menu allows you to withdraw or manually control the tip position using the stepper motor. Selecting Step Motor opens a dialog box containing the following buttons: • Tip Up: This command moves the tip up by the SPM step size displayed inside the window.
Page 212: Helpful Suggestions
Force Imaging Force Calibration (Contact Mode AFM) 3. In the Channel 1 panel select Deflection as the Data Type. 4. Maximize the Data Scale parameter. 5. Adjust the Ramp size parameter to about 1µm. 6. If the tip does not reach the sample surface (for example, see Figure 11.4a, between points 2 and 3), slowly increase the Z scan start value.
Page 213: Figure 11.4B False Engagement (G Scanner)
Force Imaging Force Calibration (Contact Mode AFM) Figure 11.4b False Engagement (G Scanner) Retracting Extending Possible False Engage Points Deflection 0.48 V/div Setpoint Z Position - 9.27 V/div Motor Control Motor Control > Tip Up and Tip Down buttons provide coarse adjustment of Z center voltage. With these buttons the SPM head moves vertically.
Page 214: Advanced Techniques
Force Imaging Force Calibration (Contact Mode AFM) 11.4.3 Advanced Techniques Sensitivity Determination The Deﬂection Sensitivity allows conversion from the raw photodiode signal (in Volts) to deﬂection of the cantilever (in nm), and is normally set from the Force Calibration mode. The sensitivity must be calibrated before accurate deﬂection data can be obtained.
Page 215 Force Imaging Force Calibration (Contact Mode AFM) Note: Deﬂection Sensitivity can be expressed in terms of the photodiode voltage versus the distance traveled by the piezo, or the photodiode voltage versus the voltage applied to the piezo, depending on the setting of the Units parameter. Force Minimization Force Calibration mode allows minimization of the contact force of the cantilever on the sample surface.
Page 216: Figure 11.4D Computing Contact Force
Force Imaging Force Calibration (Contact Mode AFM) Calculating Contact Force The force curve clearly shows the relationship between the setpoint and the deﬂection of the cantilever. Because the setpoint deﬁnes the value of the deﬂection signal maintained by the feedback loop, the force curve can be used to calculate the contact force of the tip on the sample if the spring-constant, , of the cantilever is known.
Page 217 Force Imaging Force Calibration (Contact Mode AFM) Force calculations are not as straightforward on images captured with the Data type set to Deﬂection. When collecting deﬂection data, the feedback gains are ideally set low so the sample stays at a nearly constant position relative to the cantilever holder. In this case, the cantilever deﬂection (and therefore the force applied to the sample) varies as features on the surface are encountered.
Page 218: Interpreting Force Curves
The examples in Figure 11.4e represent some of the general variations in force curves. For more information regarding force imaging, refer to Veeco’s application note Probing Nano-Scale Forces with the Atomic Force Microscope. Figure 11.4e Force Curve Examples...
Page 219: Force Calibration (Tappingmode)
Force Imaging Force Calibration (TappingMode) 11.5 Force Calibration (TappingMode) CAUTION: Because TappingMode cantilevers are relatively stiff, Force Mode can potentially damage the tip and/or surface. Before using Force Calibration, read and understand the following section. Force Mode allows the imaging of forces between the tip and surface, including chemical bonds, electrostatic forces, surface tension and magnetic forces.
Page 220: Figure 11.5A Piezo Extension Versus Rms Amplitude And Deflection
Force Imaging Force Calibration (TappingMode) Figure 11.5a Piezo Extension Versus RMS Amplitude and Deﬂection Piezo extension Piezo retraction Tip is clear of the surface z - 10.00nm/div z - 10.00nm/div Figure 11.5a illustrates a two-channel TappingMode force plot. The vertical axes of the graphs represent the amplitude (top) and TM deﬂection signal (bottom) of the cantilever.
Page 221: Obtaining A Force Plot (Tappingmode)
Force Imaging Force Calibration (TappingMode) When the piezo turns around and begins to retract, the oscillation amplitude of the cantilever increases until the tip is free of the surface, leveling off at the free-air amplitude (point 5). Channel 2 (bottom) in Figure 11.5a plots average cantilever deﬂection (TM deﬂection) versus piezo extension.
Page 222 Force Imaging Force Calibration (TappingMode) 5. Set the Main Controls and Channel 1 panel parameters to the settings shown in Figure 11.5b. Note: The Sensitivity value shown in Figure 11.5b may differ from yours. Figure 11.5b TappingMode Force Plot Parameter Settings (Force Calibrate) 6.
Page 223: High Contact Force
Force Imaging Force Calibration (TappingMode) 11.5.3 High Contact Force Figure 11.5c shows a curve produced when the tip pushes too far into the sample. The ﬂat portion on the left side of the amplitude curve in Figure 11.5c occurs because the tip is so close to the surface that it no longer vibrates.
Page 224: Force Modulation
Force Imaging Force Modulation 11.6 Force Modulation 11.6.1 Introduction This section describes the operation of force modulation mode, which you can use to image local sample stiffness or elasticity. This method is useful for imaging composite materials or soft samples on hard substrates where you can obtain contrast between regions of different elasticity.
Page 225: Selecting A Force Modulation Tip
It may take experimentation to ﬁnd a cantilever that matches the sample's requirements. For rubber and plastic samples Veeco recommends using 225µm long force modulation (Model # FESP) silicon cantilevers. For more delicate, samples, use 450µm long silicon cantilevers or silicon nitride cantilevers.
Page 226: Operating Principle
Force Imaging Force Modulation 11.6.3 Operating Principle Force modulation mode is very similar to Contact Mode AFM. The NanoScope system scans the cantilever over the sample surface while trying to keep the cantilever deﬂection constant. The deﬂection setpoint determines the average deﬂection during operation. In addition, the cantilever is oscillated up and down by a piezoelectric bimorph in the tipholder so that the tip indents slightly into the sample surface as it is scanned across the surface.
Page 227: Figure 11.6C Auto Tune Controls Panel
Force Imaging Force Modulation 8. Find the Bimorph Resonant Frequency: The cantilever is oscillated by a small piezoelectric bimorph mounted in the cantilever holder. For Force Modulation, oscillate the bimorph at or near its resonant frequency. The bimorph resonance frequency is usually the largest peak in the 5-30kHz range.
Page 228: Figure 11.6D Typical Frequency Sweep Plot
Force Imaging Force Modulation Figure 11.6d Typical Frequency Sweep Plot Peaks due to cantilever Peaks due to bimorph Note: The large drive amplitude is necessary because peaks are smaller than normally seen during TappingMode operation. This is due to the cantilever not at resonance;...
Page 229: Figure 11.6E Correctly Tuned Force Modulation Frequency
Force Imaging Force Modulation n. Adjust the Drive amplitude so the maximum response amplitude is about 1V. Recenter the peak if necessary. Figure 11.6e Correctly Tuned Force Modulation Frequency Note: You may also change the Drive Frequency by clicking on the Drive Frequency parameter on the control monitor’s Feedback Controls panel, and entering a new value.
Page 230 Force Imaging Force Modulation 14. Adjust the Integral Gain, Proportional Gain, Setpoint, and Scan Speed to obtain a good topography (Height) image. For force modulation operation, set the Integral Gain and Proportional Gain to values of 1-10 and set the Setpoint as low as possible using the cursor keys (or by typing in new Setpoint values) until the cantilever pulls off the surface and the Z- center voltage jumps to -220V.
Page 231: Notes About Artifacts
Force Imaging Force Modulation 5. The value of the Drive amplitude may also affect the Contact Mode AFM image, causing the system to go into unwanted oscillations. If the Drive amplitude changes by a large amount, readjust the Integral gain and Proportional gain. Set the gains as high as possible to track the sample topography, but not so high that they cause oscillation due to the bimorph oscillation.
Page 232: Figure 11.6F Friction On Force Modulation Images
Force Imaging Force Modulation Figure 11.6f Friction on Force Modulation Images tip moves down and left substrate moves down Effect of friction on force modulation images Tip Shape The amount of indentation into a surface for a given applied force depends on the shape of the cantilever tip.
Page 233: Force Modulation With Negative Liftmode
AFM force modulation. This method is especially suited for softer materials, yielding higher resolution. Best results using negative LiftMode are obtained on relatively smooth samples (< 500nm vertical features); however, Veeco encourages experimenting with this technique on rougher surfaces as well. A general procedure for Force Modulation with “Negative LiftMode” is...
Page 234: Obtain A Tappingmode Image
Force Imaging Force Modulation with ‘Negative LiftMode’ 11.7.2 Obtain a TappingMode Image While negative LiftMode force modulation data is imaged using Channel 2, height data is obtained using TappingMode on Channel 1. You must obtain a satisfactory TappingMode image to generate good data.
Page 235: Force Volume
Z-positions and at thousands of XY positions during a single image scan, correlation of surface topography to interaction force, better quantization of the interaction force, and new methods of analysis. For detailed information regarding force volume imaging, contact Veeco for a copy of Support Note 240A, Force Volume.
Page 237: Interleave Scanning And Liftmode
Chapter 12 Interleave Scanning and LiftMode The following sections are included in this chapter: • Preface: Interleave Scanning & LiftMode: Section 12.1 • Interleave Mode Description: Section 12.2 • Lift Mode Description: Section 12.3 • Operation of Interleave Scanning / Lift Mode: Section 12.4 •...
Page 238: Preface: Interleave Scanning & Liftmode
Interleave Scanning and LiftMode Preface: Interleave Scanning & LiftMode 12.1 Preface: Interleave Scanning & LiftMode Interleave is an advanced feature of NanoScope software which allows the simultaneous acquisition of two data types. Enabling Interleave alters the scan pattern of the piezo. After each main scan line trace and retrace (in which topography is typically measured), a second (Interleave) trace and retrace is made with data acquired to produce an image concurrently with the main scan.
Page 239: Interleave Mode Description
Interleave Scanning and LiftMode Interleave Mode Description 12.2 Interleave Mode Description Enabling Interleave changes the scan pattern of the tip relative to the imaged area. With Interleave mode disabled, the tip scans back and forth in the fast scan direction while slowly moving in the orthogonal direction as shown on the left of Figure 12.2a.
Page 240: Lift Mode Description
Interleave Scanning and LiftMode Lift Mode Description 12.3 Lift Mode Description With the Interleave scan option set to Lift, the motion of the tip during the Interleave trace and retrace is as shown in Figure 12.3a. Figure 12.3a LiftMode Proﬁles Lift Trace Lift Main Trace...
Page 241 Interleave Scanning and LiftMode Operation of Interleave Scanning / Lift Mode Note that certain constraints are imposed: scan sizes, offsets, angles, and rates and numbers of samples per scan line are the same for the main and interleave data, and the imaging context (contact, TappingMode, or force modulation) must also match.
Page 242: Use Of Liftmode With Tappingmode
Interleave Scanning and LiftMode Use of LiftMode with TappingMode 12.5 Use of LiftMode with TappingMode There are additional considerations when using LiftMode with TappingMode. 12.5.1 Main Drive Amplitude and Frequency selection As usual, these parameters are set in Cantilever Tune before engaging. It is helpful to keep in mind the measurements to be done in LiftMode when setting these values.
Page 243: Interleave Drive Amplitude And Frequency Selection
Main and Interleave scanning. If using scan rates above a few hertz, it may be advantageous to remove or disable the ﬁlter. For more information on how to disable the ﬁlter, contact Veeco technical support.
Page 244: Cantilever Oscillation Amplitude
Interleave Scanning and LiftMode Use of LiftMode with TappingMode 12.5.5 Cantilever Oscillation Amplitude The selection of the oscillation amplitude in LiftMode depends on the quantity to be measured. For force gradients which are small in magnitude but occur over relatively large distances (sometimes hundreds of nm, as with magnetic or electric forces), the oscillation amplitude can be large, which for some applications may be beneﬁcial.
Page 245: Magnetic Force (Mfm) Imaging
Chapter 12. Please review those sections prior to attempting MFM. Best results will be obtained with either the Digital Instruments Veeco Basic Extender Module or the Quadrex Extender Module. These hardware units allows phase detection and frequency modulation for optimal MFM imaging.
Page 246: Magnetic Force Imaging Theory
A more extensive discussion of force gradient detection and MFM imaging is given in the reprint Magnetic Force Microscopy: Recent Advances and Applications. Contact Veeco to obtain a copy. Note: In the instructions below, steps speciﬁc to phase and amplitude imaging are described independently.
Page 247: Mfm Using Interleave Scanning And Liftmode
(metal-evaporated video tape). Standard tape samples are provided with purchase of MFM probes, and can be obtained free of charge from Veeco. Other samples can also be used; however, you will not have the beneﬁt of comparing your results with the images shown here. Obtaining a good image of the tape sample will familiarize you with Interleave and MFM techniques and provide a check that the system is correctly tuned to image magnetic samples of interest.
Page 248: Procedure
Extender Electronics Module (Basic Extender) and Quadrex Extender Electronics Module (Quadrex Extender). (Microscopes without an Extender addition cannot utilize phase detection; for more information, contact Veeco.) The design of the NanoScope IV integrates the Quadrex Extender. Phase detection and frequency modulation detection are superior methods for magnetic force imaging, offering greater ease of use, better signal-to-noise ratios, and reduced artifact content as compared to amplitude detection.
Page 249: Figure 13.2B Shift In Phase At Fixed Drive Frequency
Magnetic Force (MFM) Imaging MFM Using Interleave Scanning and LiftMode To correctly track the cantilever phase, the Phase offset parameter must be adjusted. This is automatically done in AutoTune; alternatively, Zero Phase can be selected from the Channel 2 panel. The phase curve should appear as in Figure 13.2a, decreasing with increasing frequency, and crossing the center line (corresponding to a 90°...
Page 250: Figure 13.2C Cantilever Tune For Amplitude Detection
Magnetic Force (MFM) Imaging MFM Using Interleave Scanning and LiftMode Figure 13.2c Cantilever Tune for Amplitude Detection Figure 13.2d Shift in amplitude at ﬁxed drive frequency ∆F Drive Frequency 4. Adjust the Drive Amplitude so that the RMS voltage response of the photodetector is approximately 2V.
Page 251: Figure 13.2E Topographic (Left) And Magnetic Force Gradient Image (Right) Of Metal Evaporated Tape At 100Nm Lift Scan Height
Magnetic Force (MFM) Imaging MFM Using Interleave Scanning and LiftMode 9. Engage the AFM and make the necessary adjustments to obtain a good topographical image while displaying height data. Use the highest possible Setpoint to ensure that the tip is contacting the surface only lightly.
Page 252: Frequency Modulation
(this may be done by either the customer or a factory representative). Detailed installation instructions are provided with the new hardware when shipped. For more information, contact Veeco. The Basic Extender box is equipped with a slider switch for switching internal electronics between Dimension-series and MultiMode SPM signals.
Page 253: Quadrex Extender
Extender-compatible microscope electronics are required to permit operation of the phase detection extender option. Standard electronics on these microscopes require hardware upgrades. Consult your Veeco sales representative for details. • Turn off the power to the NanoScope controller whenever connecting or disconnecting the Extender.
Page 254: Software Setup Configuration (Basic, Quadrex Or Nsiv)
Magnetic Force (MFM) Imaging Software Setup Conﬁguration (Basic, Quadrex or NSIV) 13.4 Software Setup Conﬁguration (Basic, Quadrex or NSIV) 1. Select di > Microscope Select to display the Microscope Select dialog box (see Figure 13.4a). Figure 13.4a Microscope Select Dialog Box 2.
Page 255: Saturation In Amplitude Detection
Magnetic Force (MFM) Imaging Advanced Topics 13.5.2 Saturation in Amplitude Detection If using amplitude detection, the magnetic force image can saturate (appear completely featureless) if the Interleave Drive Amplitude is signiﬁcantly different than the Drive Amplitude in the main scan. Adjust the Interleave Setpoint to restore the image. (Note that the Interleave Setpoint has no physical effect in LiftMode since there is no surface feedback during the lift pass.
Page 256: Fine Tuning Interleave Controls
Magnetic Force (MFM) Imaging Advanced Topics is usually not beneﬁcial to use Lift scan heights much smaller than the surface roughness. Users are encouraged to experiment for the best images on their samples. The ultimate lateral resolution of MFM is near 20nm. Resolution is affected by properties of the tip, including mechanical sharpness and magnetic structure.
Page 257 Magnetic Force (MFM) Imaging Advanced Topics In LiftMode, the Interleave Drive Amplitude can often be set to a value larger than in the main scan, thus giving optimal signal-to-noise. In some cases this is beneﬁcial as long as the Drive Amplitude is not increased to the extent that the tip strikes the surface on the low point of its swing.
Page 258: Figure 13.6B Tip Heights And Oscillation Amplitudes In Tappingmode And Liftmode
Magnetic Force (MFM) Imaging Advanced Topics Setpoint For the most reproducible results, it is best to use a consistent setpoint. In LiftMode, the total tip- sample distance h is the sum of the average tip-sample distance in TappingMode h , and the lift scan height h (see Figure...
Page 259: Electric Force (Efm) Imaging
Chapter 14 Electric Force (EFM) Imaging The following sections are included in this chapter: • Electric Force Microscopy Overview: Section 14.1 • Electric Field Gradient Imaging Overview: Section 14.1.1 • Surface Potential Imaging Overview: Section 14.1.2 • Electric Field Gradient Detection—Theory: Section 14.2 •...
Page 260: Electric Force Microscopy Overview
Electric Force (EFM) Imaging Electric Force Microscopy Overview 14.1 Electric Force Microscopy Overview Note: If you have an extender electronics module (Basic or Quadrex) or a NanoScope IV, please consult the provided documentation associated with these options, prior to engaging in electric force microscopy. This chapter describes how to perform electric force microscopy (EFM) imaging on a MultiMode SPM system.
Page 261: Electric Field Gradient Imaging Overview
Electric Force (EFM) Imaging Electric Force Microscopy Overview Figure 14.1b EFM LiftMode principles Force Gradient Scope Data (Interleave scan) Topographic Scope Data (Main scan) Electric Fields Cantilever measures surface topography on first (main) scan. Cantilever ascends to lift scan height. Cantilever follows stored surface topography at the lift height above sample while responding to electric influences on second (interleave) scan.
Page 262: Surface Potential Imaging Overview
Electric Force (EFM) Imaging Electric Field Gradient Detection—Theory 14.1.2 Surface Potential Imaging Overview Surface potential imaging measures the effective surface voltage of the sample by adjusting the voltage on the tip so that it feels a minimum electric force from the sample. (In this state, the voltage on the tip and sample is the same.) Samples for surface potential measurements should have an equivalent surface voltage of less than ±10V, and operation is easiest for voltage ranges of ±5V.
Page 263: Figure 14.2B Diagram Of Extender Electronics Modules In Phase And Frequency
Electric Force (EFM) Imaging Electric Field Gradient Detection—Theory All of the above methods rely on the change in resonant frequency of the cantilever due to vertical force gradients from the sample. Figure 14.2a shows a diagram of how the Basic Extender Module provides the signal enhancement and feedback allowing gradient detection.
Page 264: Electric Field Gradient Detection Preparation
Conﬁguration sections. • A modiﬁed cantilever is required to bias the tip in EFM. Contact Veeco tech support for more information. When it is necessary to apply voltage to the tip or sample, minor changes must be made to the jumpers in the microscope’s baseplate and the toggle switches on the Basic Extender Module (if...
Page 265: Figure 14.3A Diagram Of Multimode Baseplate Showing Location And Orientation Of
Electric Force (EFM) Imaging Electric Field Gradient Detection—Preparation Figure 14.3a Diagram of MultiMode baseplate showing location and orientation of jumpers Jumpers, inside baseplate window 1. Carefully examine the following figures and identify which jumper configuration, if any, is appropriate for your application. 2.
Page 266: Jumper Configurations For Systems Without The Basic Extender Module
Note: In all conﬁgurations which apply voltage to the tip, an E-ﬁeld cantilever holder is required. Contact Veeco for more information. Enabling the Analog 2 Voltage Line The “Analog 2” voltage line is normally used by the NanoScope to control the attenuation (1x or 8x) of the main feedback signal.
Page 267: Figure 14.3C Jumper Configuration For Application Of Voltage To Tip (For Systems Without The Basic Extender Module)
Electric Force (EFM) Imaging Electric Field Gradient Detection—Preparation Figure 14.3c Jumper conﬁguration for application of voltage to tip (for systems without the Basic Extender Module). Ground Piezo Cap Analog 2 Analog 2 Sample Gain Select Analog 2 To AFM Tip Auxiliary D (to NanoScope III controller) Indicates jumpers Rev.
Page 268: Figure 14.3D Jumper Configuration For Application Of Voltage To Sample (For Systems Without The Basic Extender Module)
Electric Force (EFM) Imaging Electric Field Gradient Detection—Preparation Voltage Applied to the Sample The jumper conﬁguration in Figure 14.3d connects the Analog 2 signal from the NanoScope III controller (± 12 VDC range) to the sample chuck. Enabling the Analog 2 Voltage Line The “Analog 2”...
Page 269: Figure 14.3E Jumper Configuration For Applying External Voltage To Tip (For Systems Without The Basic Extender Module)
14.3e. Note: In all conﬁgurations which apply voltage to the tip, an E-ﬁeld cantilever holder is required. Contact Veeco for more information. Figure 14.3e Jumper conﬁguration for applying external voltage to tip (for systems without the Basic Extender Module). Ground...
Page 270: Figure 14.3F Jumper Configuration For Applying External Voltage To Sample (For Systems Without The Basic Extender Module)
Electric Force (EFM) Imaging Electric Field Gradient Detection—Preparation External Voltage Source Applied to the Sample In some cases, it may be advantageous to use voltages greater than 12 VDC, or to use a pulsed power supply. If an external source of voltage is to be applied to the sample, conﬁgure jumpers as shown in Figure 14.3f.
Page 271: Jumper Configurations For Systems With The Basic Extender Module
Electric Force (EFM) Imaging Electric Field Gradient Detection—Preparation 14.3.2 Jumper Conﬁgurations for systems with the Basic Extender Module REMINDER: Power down the microscope and turn off all peripherals. Unplug the NanoScope III control and power cables from the system before attempting to adjust jumper conﬁgurations. As shipped from the factory, systems with the Basic Extender option, should have an original baseplate jumper conﬁguration as shown in Figure...
Page 272: Figure 14.3H Jumper Configuration For Application Of Voltage To Tip (For Systems With The Basic Extender Module)
Note: In all conﬁgurations which apply voltage to the tip, an E-ﬁeld cantilever holder is required. Contact Veeco for more information. Enabling the Analog 2 Voltage Line The “Analog 2” voltage line is normally used by the NanoScope to control the attenuation (1x or 8x) of the main feedback signal.
Page 273: Figure 14.3I Jumper Configuration For Application Of Voltage To Sample (For Systems With The Basic Extender Module)
Electric Force (EFM) Imaging Electric Field Gradient Detection—Preparation Voltage Applied to the Sample The jumper conﬁguration in Figure 14.3i connects the Analog 2 signal from the NanoScope III controller (± 12 VDC range) to the sample. Enabling the Analog 2 Voltage Line The “Analog 2”...
Page 274: Figure 14.3J Jumper Configuration For Applying External Voltage To Tip (For Systems With The Basic Extender Module)
14.3j. Note: In all conﬁgurations which apply voltage to the tip, an E-ﬁeld cantilever holder is required. Contact Veeco for more information. Figure 14.3j Jumper conﬁguration for applying external voltage to tip (for systems with the Basic Extender Module). Ground...
Page 275: Figure 14.3K Jumper Configuration For Applying External Voltage To Sample (For Systems With The Basic Extender Module)
Electric Force (EFM) Imaging Electric Field Gradient Detection—Preparation External Voltage Source Applied to the Sample In some cases, it may be advantageous to utilize voltages greater than 12 VDC, or to utilize a pulsed power supply. If an external source of voltage is to be applied to the sample, conﬁgure jumpers as shown in Figure 14.3k.
Page 276: Electric Field Gradient Detection Procedures
Electric Force (EFM) Imaging Electric Field Gradient Detection—Procedures 14.4 Electric Field Gradient Detection—Procedures Note: Amplitude detection is the only procedure described here that can be done without the Basic Extender Module; however, this method is no longer recommended (see “Without Basic Extender Module” on page 259). 1.
Page 277: Phase Detection
Electric Force (EFM) Imaging Electric Field Gradient Detection—Procedures 3. Mount a metal-coated NanoProbe cantilever into the electric field cantilever holder. MFM- style cantilevers (225µm long, with resonant frequencies around 70kHz) usually work well. It is also possible to deposit custom coatings on model FESP silicon TappingMode cantilevers.
Page 278: Figure 14.4C Shift In Phase At Fixed Drive Frequency
Electric Force (EFM) Imaging Electric Field Gradient Detection—Procedures Figure 14.4c Shift in Phase at Fixed Drive Frequency ∆F ∆φ Drive Frequency • Under Interleave Controls set the Lift start height to 0nm, and Lift scan height to 100nm. (The lift height can later be optimized.) Set the remaining Interleave parameters (Setpoint, Drive amplitude, Drive frequency, and gains) to the main Feedback Controls values.
Page 279: Amplitude Detection
Electric Force (EFM) Imaging Electric Field Gradient Detection—Procedures • Adjust the sample or tip voltage to conﬁrm that contrast is due to electrical force gradients. On very rough samples, contrast in LiftMode images may be from air damping between the tip and surface. It is often useful to look at the phase data in Scope Mode while adjusting the tip or sample voltage up and down.
Page 280: Figure 14.4E Amplitude Detection Cantilever Tune (Basic Extender Module Not Installed)
Electric Force (EFM) Imaging Electric Field Gradient Detection—Procedures • Set the Drive frequency to the left side of the cantilever resonance curve, as shown in Figure 14.4e below. Figure 14.4e Amplitude Detection Cantilever Tune (Basic Extender Module not Installed). • For maximum sensitivity, set the Drive frequency to the steepest part of the resonance curve.
Page 281: Surface Potential Detection Theory
Electric Force (EFM) Imaging Surface Potential Detection—Theory 14.5 Surface Potential Detection—Theory Note: Surface potential detection EFM is only possible using the one of the extender modules or the NanoScope IV controller. This section does not apply to microscopes which are not equipped with the Basic or Quadrex Modules, or the NanoScope IV controller.
Page 282: Figure 14.5A Simplified Block Diagram Of Basic Extender Module In Surface
Electric Force (EFM) Imaging Surface Potential Detection—Theory Figure 14.5a Simpliﬁed Block Diagram of Basic Extender Module in Surface Potential Mode Cantilever Deflection Signal Photodiode Signal Amplitude Signal Detector Lock-in Amplifier Reference Signals to Signal Servo Controller Laser NanoScope Beam (Feedback loop adjusts DC tip DC Voltage Photo-...
Page 283: Surface Potential Detection Preparation
Electric Force (EFM) Imaging Surface Potential Detection—Preparation 14.6 Surface Potential Detection—Preparation It is often desirable to apply a voltage to one or more areas of a sample. This may be done in two ways: by connecting a voltage to the sample mounting chuck, or by making direct contact to the sample.
Page 284: Applying Voltage To The Sample Directly
Electric Force (EFM) Imaging Surface Potential Detection—Preparation 14.6.1 Applying Voltage to the Sample Directly When voltage is applied directly to the sample, there is no need to reconﬁgure the jumpers. They should remain jumpered as shipped from the factory (Figure 14.6a), and the sample should be electrically insulated from the chuck.
Page 285: Surface Potential Imaging Procedure
Electric Force (EFM) Imaging Surface Potential Imaging—Procedure A current-limiting resistor (e.g., 10–100MΩ) should be placed in series with the external voltage supply to protect the tip and sample from damage. Current-limited power supplies may also be used. Voltage leads should be connected to pins on the header using soldered, push-on connectors. Do not solder leads directly to the header pins.
Page 286 Electric Force (EFM) Imaging Surface Potential Imaging—Procedure Table 14.7a Basic Extender Module toggle switch settings for surface potential imaging. Mode Tip or Sample Voltage FM/Phase Surface GND/Surface Analog 2 Potential Potential TappingMode √ √ Contact AFM Surface √ √ Potential Apply voltage to tip or sam- ple (Use for...
Page 287 Electric Force (EFM) Imaging Surface Potential Imaging—Procedure 7. Select the Interleave Controls command. This brings up a new set of scan parameters that are used for the interleaved scan where surface potential is measured. Different values from those on the main scan may be entered for any of the interleaved scan parameter. To fix any of the parameters so they are the same on the main and interleave scans, click on the green bullets to the left of particular parameter.
Page 288 Electric Force (EFM) Imaging Surface Potential Imaging—Procedure 13. Optimize the lift heights. Set the Lift scan height at the smallest value possible that does not make the Potential feedback loop unstable or cause the tip to crash into the sample surface. When the tip crashes into the surface during the Potential measurement, dark or light streaks appear in the Potential image.
Page 289: Troubleshooting The Surface Potential Feedback Loop
Electric Force (EFM) Imaging Surface Potential Imaging—Procedure 14.7.1 Troubleshooting the Surface Potential Feedback Loop The surface potential signal feedback loop can be unstable. This instability can cause the potential signal to oscillate or become stuck at either +10V or -10V. Here are some tips to see if the feedback loop is working properly with no oscillation: •...
Page 291: Calibration, Maintenance, Troubleshooting And Warranty
Chapter 15 Calibration, Maintenance, Troubleshooting and Warranty This chapter provides detailed instructions for the ﬁne calibration of Veeco MultiMode SPMs. Additionally, the latter part of the chapter focuses on problems commonly encountered during operation of the microscope and then concludes with maintenance procedures for the MultiMode SPM adjustment screws.
Page 292 Calibration, Maintenance, Troubleshooting and Warranty • X-Y Calibration using Capture Calibration and Autocalibration: Section 15.5 • Capture Calibration: Section 15.5.1 • Autocalibration: Section 15.6 • Fine-tuning for X-Y Calibration: Section 15.7 • Prepare System for Fine-Tuning: Section 15.7.1 • Measure Horizontally at 440V Scan Size: Section 15.7.2 •...
Page 293 Calibration, Maintenance, Troubleshooting and Warranty • Contact AFM Troubleshooting: Section 15.11 • False engagement: Section 15.11.1 • Head appears engaged but does not track surface features: Section 15.11.2 • Head does not engage: Section 15.11.3 • Head engages immediately: Section 15.11.4 •...
Page 294 Calibration, Maintenance, Troubleshooting and Warranty • Adjustment Screw Maintenance Procedure: Section 15.14 • Inspection: Section 15.14.1 • Remove Adjustment Screws: Section 15.14.2 • Inspect for Physical Damage: Section 15.14.3 • Clean Guide Bushings: Section 15.14.4 • Lubricate: Section 15.14.5 • Reinstall: Section 15.14.6 •...
Page 295: Spm Calibration Overview
15.1 SPM Calibration Overview Veeco employs a software-guided calibration procedure for all its microscopes. The procedural particulars of how calibration is executed using NanoScope software are beyond the scope of this document and include proprietary methods exclusive to Veeco. The calibration procedure is...
Page 296: Theory Behind Calibration
Every 6 months Critical Height Measurements All Years Monthly Note: Small Scan Size Calibration: If using scan sizes of 5µm or smaller, Veeco recommends calibrating the scanner for small scan sizes. Contact Veeco for further instructions. 15.1.1 Theory Behind Calibration Scanners typically consist of a hollow tube made of piezoelectric material such as PZT (lead zirconium titanate).
Page 297: Figure 15.1A Scanner Crystal Voltage And Photodiode Voltage
Calibration, Maintenance, Troubleshooting and Warranty SPM Calibration Overview Figure 15.1a Scanner Crystal Voltage and Photodiode Voltage Photodiode voltage Laser Photodiode array Cantilever 0 VDC +220 VDC -220 VDC Scanner +3.0 Detector Sensitivity -3.0 -220 +220 Scanner Voltage The Microscope > Calibrate > Scanner function displays the Scanner Calibration dialog box, allowing users to enter the sensitivity of their scanner’s X-Y axes.
Page 298: Figure 15.1B Effect Of Nonlinearity And Hysteresis
Calibration, Maintenance, Troubleshooting and Warranty SPM Calibration Overview Consider the sensitivity curve represented here: 440 V 150 V Scanner Movement (nm) This curve typiﬁes scanner sensitivity across the full range of movement. The vertical axis denotes voltage applied to the scanner. The horizontal axis denotes scanner movement. At higher voltages, the scanner’s sensitivity increases (i.e., more movement per voltage applied).
Page 299 Movement Time Through rigorous quality control of its scanner piezos, Veeco has achieved excellent modeling of scanner characteristics. Two calibration points are typically used for ﬁne-tuning: 150 and 440V. (A third point is assumed at 0 nm/V.) These three points yield a second-order sensitivity curve to ensure accurate measurements throughout a broad range of scanner movements.
Page 300: Calibration References
This task is accomplished with the use of a calibration reference (see Figure 15.1c). Figure 15.1c Veeco Silicon Calibration Reference 200nm deep 10µm 10µm This calibration reference consists of a silicon substrate having a regular series of pits, each 200nm deep.
Page 301: Calibration Setup
CD shipped with every system. Individually purchased scanners are shipped with a head/ scanner disk containing backup ﬁles, or a hard copy of the scanner parameters. In the event that ﬁles are not found, fax or call Veeco for scanner calibration records. 15.2.2 Align Calibration Reference Load the silicon calibration reference into the SPM.
Page 302: Set Realtime Parameters
Calibration, Maintenance, Troubleshooting and Warranty Calibration Setup 15.2.3 Set Realtime Parameters Set parameters in the control panels to the following values: Panel Parameter Setting Scan Controls Scan Size 440 V X offset 0.00nm Y offset 0.00nm Scan angle 0.00 deg Scan rate 2.44Hz Number of samples...
Page 303: Check Sample Orthogonality
Calibration, Maintenance, Troubleshooting and Warranty Check Sample Orthogonality 15.3 Check Sample Orthogonality Check the sample scan for orthogonality along both the X- and Y-axes. If the scan is aligned along one axis of the scan but not another, it may be necessary to adjust the microscope’s Orthogonality parameter in the Scanner Calibration panel.
Page 304: Linearity Correction Procedure
Calibration, Maintenance, Troubleshooting and Warranty Linearity Correction Procedure 3. Click to exit the Scanner Calibration panel 4. Capture another image and re-measure the angle. 5. Repeat correction of Orthogonality until the scanned image shows less than 0.5º of error. Note: After a major change to the orthogonality parameter, you may need to physically realign the calibration standard to the image frame.
Page 305: Figure 15.4A Fast Scan Linearization: Mag0
Calibration, Maintenance, Troubleshooting and Warranty Linearity Correction Procedure Adjust Fast Mag0 1. After engaging, click on Microscope > Calibrate > Scanner to open the Scanner Calibration window. As parameters values are changed, the effects will be seen on the display monitor. 2.
Page 306: Figure 15.4B Fast Scan Linearization: Arg
Calibration, Maintenance, Troubleshooting and Warranty Linearity Correction Procedure Adjusting Fast Arg 1. Once the beginning third of the scan is equal to the end third, check to see if the center needs adjusting. 2. If the center features are too large for the box, decrease the Fast arg value. If the center features are too small, increase the Fast arg value.
Page 307: Adjusting Fast Mag1
Calibration, Maintenance, Troubleshooting and Warranty Linearity Correction Procedure 5. If the features of the end third are too large for the box, decrease the parameter. If the features are too small, increase the parameter. Note: Compare only parts of the current scan, not the previous scan. Figure 15.4c Slow Scan Linearization: Arg Slow Arg Too Small Slow Arg Too Large...
Page 308: Adjust Slow Mag1
Calibration, Maintenance, Troubleshooting and Warranty Linearity Correction Procedure 4. On the display monitor, select Dual Trace. If the two scope traces do not overlap, Fast mag1 needs adjusting. 5. On the Scan Controls panel, select Slow scan axis. When tall features appear on the scope trace, press the keyboard right or left arrow key to switch the Slow scan axis to Disabled.
Page 309: X-Y Calibration Using Capture Calibration And Autocalibration
Calibration, Maintenance, Troubleshooting and Warranty X-Y Calibration using Capture Calibration and Autocalibration 5. If the end of the scan is larger than the beginning, decrease the Slow mag1 value. If the end is too small, increase the value of Slow mag1. 6.
Page 310: Figure 15.5B Capture Control Dialog Box
Calibration, Maintenance, Troubleshooting and Warranty X-Y Calibration using Capture Calibration and Autocalibration 4. Click on to initiate the automatic calibration routine. CAPTURE Note: The microscope will begin an automatic series of scans on the reference which require about one hour to complete. During each scan, the scanner moves the piezo using carefully calculated movements.
Page 311: Figure 15.5C Calibration Images
Calibration, Maintenance, Troubleshooting and Warranty X-Y Calibration using Capture Calibration and Autocalibration Figure 15.5c Calibration Images 28.37 µ µ µ µ m Partial Calibration Image Improved Calibration Image Note: After the ﬁrst four images with the diagonal stripe pattern are captured, you can leave the system unattended while the program continues to completion.
Page 312: Autocalibration
Calibration, Maintenance, Troubleshooting and Warranty Autocalibration 15.6 Autocalibration After the Capture Calibration routine is completed, the user measures surface features contained within each image and enters their dimensions into the software. The software compares its estimates with the actual (user-entered) dimensions to make ﬁnal corrections. This portion of the calibration is carried out using the Ofﬂine >...
Page 313 Calibration, Maintenance, Troubleshooting and Warranty Autocalibration 3. Use the mouse to draw a line on the image. The line should be drawn to span as many features as possible, preferably connecting similar edges. For example, consider the following: Autocalibration Draw a vertical line In this example, a line is drawn from the bottom edge of one feature to the bottom edge of another feature four rows away—a distance of 40µm.
Page 314: Fine-Tuning For X-Y Calibration
Calibration, Maintenance, Troubleshooting and Warranty Fine-tuning for X-Y Calibration 15.7 Fine-tuning for X-Y Calibration Fine-tuning is usually performed at two Scan size settings: 150 and 440V. Both horizontal and vertical measurements of sample features are made, then compared with actual distances. Based upon this comparison, computer parameters are ﬁne tuned.
Page 315: Figure 15.7A Calibration Horizontal Reference
Calibration, Maintenance, Troubleshooting and Warranty Fine-tuning for X-Y Calibration Figure 15.7a Calibration Horizontal Reference Draw a horizontal line. Verify that the microscope’s measured distance agrees with the known horizontal distance. If there is signiﬁcant disagreement between the two, ﬁne tuning is required; go to Step 3 below.
Page 316: Measure Vertically At 440V Scan Size
Calibration, Maintenance, Troubleshooting and Warranty Fine-tuning for X-Y Calibration Figure 15.7b Scanner Calibration Dialog Box Multiply the quotient obtained in Step 3 by the X fast sens value shown on the Scanner Calibration panel. Enter the new value. This new value adjusts the scanner’s fast scan axis to more closely match calculated distances with actual feature distances.
Page 317: Measure Horizontally At 150V Scan Size
Calibration, Maintenance, Troubleshooting and Warranty Fine-tuning for X-Y Calibration Divide the known distance by the distance displayed next to the line drawn in Step 2. Write this value down. 4. Select the Realtime > Microscope > Calibrate > Scanner function to display the Scanner Calibration dialog box.
Page 318: Measure Vertically At 150V Scan Size
Calibration, Maintenance, Troubleshooting and Warranty Fine-tuning for X-Y Calibration Calculation Method 1. Select Realtime > Microscope > Calibrate > Scanner to display the Scanner Calibration dialog box. 2. Record the X fast derate or Y slow derate value. 3. Perform the following calculation where s is the X fast Sens or Y slow Sens value; a is the actual distance;...
Page 319: Calibrating Z
X- and Y-axes do during scanning. Furthermore, offsets affect the piezo over a period of minutes. The silicon calibration references distributed by Veeco have 200nm vertical features accurate to within ± 3 percent. The calibration reference is referred to throughout the examples provided in this section.
Page 320: Capture And Correct An Image
Calibration, Maintenance, Troubleshooting and Warranty Calibrating Z Figure 15.8a Z Calibration Image 5. Verify that the Z Center Position value shown next to the image display is close to 0 volts (±5 volts). 6. If the Z Center Position value is not close to zero, use the Realtime > Motor > Tip Up and Tip Down buttons to adjust.
Page 321: Measure Vertical Features
Calibration, Maintenance, Troubleshooting and Warranty Calibrating Z Figure 15.8b Draw a Stopband 5. Click Execute to complete the flattening procedure. 6. Quit the dialog box. 15.8.3 Measure Vertical Features With the image corrected, its vertical features may now be measured. This is performed using Depth analysis to utilize more data points.
Page 322: Figure 15.8D Draw A Cursor Box
Calibration, Maintenance, Troubleshooting and Warranty Calibrating Z 2. Go to the display screen and draw a cursor box surrounding the entire image (see Figure 15.8d). Figure 15.8d Draw a Cursor Box 3. Click in the display monitor’s top menu bar. EXECUTE Note: Height data within the drawn cursor box displays on the monitor, showing two,...
Page 323: Correct Z Sensitivity
Z sensitivity value. Note: The numerator value above (200 nm) is for Veeco 10µm silicon reference. For other calibration references, set the numerator equal to the depth of features speciﬁed by the manufacturer. Ideally, calibration references should have features with heights comparable to those being imaged and measured on samples.
Page 324: Calculate Retracted And Extended Offset Deratings
Step 5 Step Note: The measured depth should read 200nm on a Veeco 10µm silicon calibration reference. 5. Select the Realtime > Microscope > Calibrate > Z option to display the Z Calibration panel 6. Click on the Extended offset der parameter.
Page 325: Finding A Pit With An A Scanner
Calibration, Maintenance, Troubleshooting and Warranty Calibrating Z 15.8.7 Finding a Pit with an “A” Scanner Since it may be difﬁcult and/or time consuming to locate a pit in the sample using an “A” scanner, an alternate method of locating a pit is to use the Scope mode in Realtime imaging. 1.
Page 326: Calibration Of A Scanners For Atomic-Scale Measurement
Calibration, Maintenance, Troubleshooting and Warranty Calibration of “A” Scanners for Atomic-scale Measurement 15.9 Calibration of “A” Scanners for Atomic-scale Measurement The “A” scanner is the smallest scanner, with a total travel of approximately 0.4µm along each axis. Its compact design lends excellent stability for atomic scans, and requires slightly modiﬁed X-Y calibration procedures.
Page 327: Figure 15.9A Typical Atomic Scan Of Graphite. Note The Highly Regular Lattice Of The Atoms. The Cursor Line Describes A Distance Of 6.66Å
Calibration, Maintenance, Troubleshooting and Warranty Calibration of “A” Scanners for Atomic-scale Measurement 3. Engage the surface and adjust the Integral gain and Setpoint to obtain a good image. Keep the Setpoint low if possible, and the Z Center Position close to 0V. Notice that the Scan rate is set much higher (~ 61 Hz) for atomic-scale images, this to defeat some of the noise due to thermal drift.
Page 328: Calibration Of "A" Scanners For Atomic-Scale Measurement
Calibration, Maintenance, Troubleshooting and Warranty Calibration of “A” Scanners for Atomic-scale Measurement 5. Go to the Offline > View > Top View option and measure the spacings between atoms using the mouse. Depending upon whether the sample is graphite or mica, measure the spacings as shown below.
Page 329: Quick Guide To Piezo Tube Calibration
Calibration, Maintenance, Troubleshooting and Warranty Quick Guide to Piezo Tube Calibration Do not adjust the derating parameters for atomic-scale imaging, including: • X fast derate • X slow derate • Y fast derate • Y slow derate • Retracted offset der •...
Page 330: Run Autocalibration Software (Factory Operation)
Calibration, Maintenance, Troubleshooting and Warranty Quick Guide to Piezo Tube Calibration 7. Reduce the scan size to 150V and adjust the Fast and Slow mag1 values to make the image linear. Typical values are 0.6 - 1.5. 15.10.2 Run Autocalibration Software (Factory Operation) Note: You can use Fine Tune in place of Autocalibration.
Page 331: Calibrate The Z Piezo
Calibration, Maintenance, Troubleshooting and Warranty Quick Guide to Piezo Tube Calibration 6. Adjust the X Slow sens until the slow axis is correct. 15.10.4 Calibrate the Z Piezo This calibration is necessary during routine maintenance. 1. Set the Scan size to 150V. Scan rate to 2.44Hz. 2.
Page 332 Calibration, Maintenance, Troubleshooting and Warranty Quick Guide to Piezo Tube Calibration Figure 15.10a Calibration Recommended Parameters To the side of some scan parameters are the recommended scan size and scan angle setting for obtaining accurate calibration values. 440V, 90° 440V, 0° 150V, 0°...
Page 333: Contact Afm Troubleshooting
Calibration, Maintenance, Troubleshooting and Warranty Contact AFM Troubleshooting 15.11 Contact AFM Troubleshooting Depending on the operating mode being used, the symptoms and subsequent resolution may vary. For this reason, problems listed in this chapter are divided into Contact AFM (see Section 15.11) and TappingMode (see...
Page 334: Head Appears Engaged But Does Not Track Surface Features
Calibration, Maintenance, Troubleshooting and Warranty Contact AFM Troubleshooting • Check the cabling between the computer and the controller, and between the controller and the microscope. Any discontinuity in the microscope signals can cause an immediate engage. • The Setpoint may be set more negative than the vertical deﬂection (A-B) voltage (this applies only to contact AFM modes).
Page 335: Head Engages Immediately
Calibration, Maintenance, Troubleshooting and Warranty Contact AFM Troubleshooting 15.11.4 Head engages immediately If the microscope engages immediately after the Engage icon is selected, the problem may be one the following: 1) The Setpoint may be lower than the feedback voltage. Select Withdraw a few times and verify that the vertical deﬂection reads a negative voltage of -1.0 to -4.0V.
Page 336: Image Vertical Dimensions Are Not Correct
Calibration, Maintenance, Troubleshooting and Warranty Contact AFM Troubleshooting (both of which are on the same side of the chip) will have difﬁculties with the laser optics due to laser beam spillage over the side of the cantilever. This effect is more pronounced for samples which are highly reﬂective.
Page 337: Poor Image Quality
Calibration, Maintenance, Troubleshooting and Warranty Contact AFM Troubleshooting vertical drift is indicative of optical path drift, while a horizontal drift is due to a mechanical change in tip-to-sample separation. Use the following as ﬁrst steps in correcting drift: • Verify that the sample, tip and stage are all stabilized. There should be no free movement between any of these components •...
Page 338: Force Calibration Command Does Not Seem To Work
Calibration, Maintenance, Troubleshooting and Warranty Contact AFM Troubleshooting Selecting a large Scan size and a high scan rate for a few scans can “sweep” an area clear. Decreasing the Scan size to image within the “swept” area can improve the quality of atomic images.
Page 339: Tappingmode Afm Troubleshooting
Calibration, Maintenance, Troubleshooting and Warranty TappingMode AFM Troubleshooting 15.12 TappingMode AFM Troubleshooting Depending on the operating mode being used, the symptoms and subsequent resolution may vary. For this reason, problems listed in this section are divided into Contact Mode (see Section 15.11) and TappingMode (see...
Page 340: Lines Across The Image
Calibration, Maintenance, Troubleshooting and Warranty TappingMode AFM Troubleshooting Figure 15.12a Images With/Without Streaks With Streaks Without Streaks 15.12.2 Lines across the image Lines oriented in the fast scan direction can be caused by the tip sticking to the surface. This condition may be remedied by increasing the RMS voltage.
Page 341: Rings Around Features On The Surface
Calibration, Maintenance, Troubleshooting and Warranty TappingMode AFM Troubleshooting 15.12.3 Rings around features on the surface This effect might also be described as the image looking as though it is half submerged beneath water (see Figure 15.12b). This is caused by operating with a drive frequency too close to cantilever resonance.
Page 342: Multiple Or Repeating Patterns
Calibration, Maintenance, Troubleshooting and Warranty TappingMode AFM Troubleshooting 15.12.4 Multiple or repeating patterns The tip is probably chipped (see Figure 15.12c Figure 15.12d). This is usually caused by using too much tapping force on the surface, or because the tip encountered a feature too high to successfully traverse.
Page 343: Image Goes White Or Black
Thus, lateral stress on the O-ring is absent. Vertical engage scanners are available in the 125µm (“J”), and 10µm (“E”) sizes. Contact Veeco for more information. • Lightly coating the area of the O-ring which contacts the sample surface with white petrolatum or vacuum grease will allow the O-ring to slide across the surface, minimizing lateral stress.
Page 344: Leaks
15.14 Adjustment Screw Maintenance Procedure This section covers maintenance procedures for adjustment screws used on Veeco Small Sample microscopes. These screws are used to support and position the head relative to the scanner, and must be cleaned periodically to ensure smooth operation. Instructions for the removal, cleaning, lubrication and replacement of adjustment screws are included in this section.
Page 345 If screws are frozen (i.e., cannot be rotated), DO NOT attempt to force them! Return the scanner body and screws to Veeco for repair. The user should inspect screws at least every three months, more often if possible. It is a good practice to check screws whenever the scanner body is removed by turning manually and feeling for resistance.
Page 346: Remove Adjustment Screws
If this occurs, they will have to be pressed out and replaced; return to Veeco for repair. 1. Once screws are removed from the scanner body, they may be washed using methanol. Do not use strong solvents such as methyl chloride, MEK, benzene, etc.
Page 347: Clean Guide Bushings
If threads are cross-threaded or stripped, the unit will have to returned to Veeco for repair. 15.14.4 Clean Guide Bushings Plastic guide bushings are installed to stabilize screws and increase rigidity.
Page 348: Fuse Replacement Procedure
6. Using a screwdriver, press the slot in the fuse holder and rotate the fuse a 1/4 turn clockwise until the fuse is secure. 7. Order another spare fuse from Veeco. Be sure to turn off all system power before placing the spare fuse back in the holder location.
Page 349: Vertical Engagement Scanners Installation, Use, And Maintenance
Vertical Engagement Scanners—Installation, Use, and Maintenance 15.16 Vertical Engagement Scanners—Installation, Use, and Maintenance Figure 15.16a MultiMode Scanner Veeco now offers “E” and “J” scanners which permit vertical engagement without signiﬁcant lateral movement. The vertical scanners feature the following: • Completely motorized tip-sample engage. •...
Page 350: Hardware Installation
Calibration, Maintenance, Troubleshooting and Warranty Vertical Engagement Scanners—Installation, Use, and Maintenance 15.16.1 Hardware Installation Installation of the vertical scanner is very similar to earlier models. To install the vertical scanner, do the following: 1. Remove old scanner: If the SPM is engaged, disengage from the sample by clicking on the Withdraw icon several times.
Page 351: Select Scanner
Calibration, Maintenance, Troubleshooting and Warranty Vertical Engagement Scanners—Installation, Use, and Maintenance The scanner ﬁle may be copied with any name, as long as it includes a .SCN extension. Make certain the vertical scanner’s ﬁle name is not the same as a preexisting ﬁle; otherwise, it will overwrite the preexisting ﬁle.
Page 352: Troubleshooting The Vertical Engagement Scanners
A leadscrew cleaning procedure is detailed in Support Note 216 available from Veeco. Note: If screw is frozen (i.e., cannot be rotated), DO NOT attempt to force it! Return the scanner body and screw to Veeco for repair. MultiMode SPM Instruction Manual Rev. B...
Page 353: Warranty
Veeco’s obligation under these warranties is limited to repairing or replacing at Veeco’s option defective non-expendable parts. Veeco’s obligation shall not extend to defects that do not impair service. No claim will be allowed for any defect unless Veeco has received notice of the defect within thirty days following its discovery by purchaser.
Page 354 To be eligible for the above warranties, purchaser must perform preventative maintenance in accordance with the schedule set forth in the manual provided. Veeco assumes no liability under the above warranties for equipment or system failures resulting from improper operation, improper preventative maintenance, abuse or modiﬁcations of the equipment or system from the original...
Page 355: Index
88 adjustment 195 principles of 39 — Force Cal 99 — Contact Force 101 Force Calibration 276 Contact Veeco Technical Publications 333 Capture 190 Drive amplitude 187 Data type Drive Frequency 187 force modulation 209 Force Curve Rev. B...
Page 356 Index adjustment 191 symbol 5 — — Force Modulation 204 Lateral Force Microscopy 167 — — Left Image 93 edge effects 210 operating procedure 206 — principles of 167 principles of 206 scan angle 169 Frequency Modulation with MFM 232 Lift scan height 220 Lift start height 220 Frequency Sweep 110...
Page 357 Index attention 5 sample safeguards 12 voltage 7 electrical 5 wiring 7 general operator safety 6 — Other Controls 94 laser 5 lifting 5 mechanical crushing 5 Parameters show 91 Safety Precautions 6 — Personal Injury Sample symbol 5 precautions 12 Probe menu Samples Run Continuous 190...
Page 358 Index laser hazard 5 Z scan start 184 lifting hazard 5 Zoom In 208 Zoom In 112 mechanical crushing hazard 5 safety 5 TappingMode 103 — principles of 43 — set-up 85 Tip Down 191 Tip Holder installation fixture 77 Tip Up 191 to 230 Trace 116...

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004-210-100

Veeco 004-210-000 Instruction Manual

Table of Contents

List of Figures

Chapter 1 Introduction to the Digital Instruments Multimode SPM

Chapter 2 SPM Fundamentals for the Multimode

Spm Fundamentals for the Multimode/Figure 2.1A Multimode Spm System Hardware

Chapter 3 Setup & Installation

Chapter 4 Cantilever Preparation

Chapter 5 Head, Probe and Sample Preparation

Chapter 6 Contact AFM Mode

Chapter 7 Tappingmode AFM

Chapter 8 Fluid Operation

Chapter 9 Scanning Tunneling Microscopy (STM)

Chapter 10 Lateral Force Mode

Chapter 11 Force Imaging

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