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Electric Force (EFM) Imaging

Surface Potential Imaging—Procedure

266

MultiMode SPM Instruction Manual

Rev. B

Table 14.7a   

Basic Extender Module toggle switch settings for surface potential imaging.

Note:

The toggle switch combination of Surface Potential = ON and Analog2 = ON is 

not recommended

 and can produce erratic and unde

fi

ned results.

2. Mount a sample onto the sample holder. Make any external electrical connections that are 

necessary for the sample.

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. Verify that all deposited metal adheres strongly to the silicon cantilever.

4. Set up the AFM as usual for TappingMode operation.

5. Use 

Cantilever Tune: AutoTune

 (as described in 

Step 6

 of 

Section 14.4

) to locate the 

cantilever resonant peak. Remember, however, that the Extender box has been reconfigured 
so that the phase detection circuitry now acts as a lock-in amplifier. Any procedures that are 
normally used to view or adjust the phase signal will now affect the lock-in signal instead 
(see 

Figure 14.5a

).

In this case, two curves should appear in the 

Cantilever Tune

 box: the 

amplitude

 curve in white 

and the 

lock-in

 curve in yellow. In the event you 

fi

nd more than one resonance, select a resonance 

that is sharp and clearly de

fi

ned, but not necessarily the largest. It is also helpful to select a resonant 

peak where the lock-in signal also changes very sharply across the peak. Multiple peaks can often 
be eliminated by making sure the cantilever holder is clean and the cantilever is tightly secured.

6. Engage the AFM and make the necessary adjustments for a good TappingMode image while 

displaying height data.

Mode

Tip or Sample Voltage

FM/Phase

Surface 
Potential

GND/Surface
Potential

Analog 2

TappingMode

Contact AFM

MFM

√

√

Surface 
Potential

√

√

Apply voltage 
to tip or sam-
ple (Use for 
electric 

fi

eld 

gradient 
imaging; tun-
neling AFM)

√

√

Содержание 004-210-000

Страница 1: ...09 04 All N A C Kowalski 4 31ce A 27OCT97 Chapters 3 5 and 8 168 185 189 4 22ce 14FEB97 TOC TOW Chapters 2 5 7 11 12 13 15 and Index 139 4 22 15JUL96 Released 8 MultiMode SPM Instruction Manual NanoS...

Страница 2: ...d reproduced or translated into another language without prior written consent Copyright Copyright 2004 Veeco Instruments Inc All rights reserved Trademark Acknowledgments The following are registered...

Страница 3: ...SPM 19 2 1 2 SPM Head 20 2 1 3 Scanners 21 2 1 4 Tipholders 24 2 1 5 Probes 25 2 2 Control Mechanisms and Feedback 28 2 2 1 A brief history of SPM control mechanisms 28 2 3 Feedback Gains 30 2 3 1 Pro...

Страница 4: ...reparation 69 5 1 Initial Preparation for Contact AFM Imaging 72 5 1 1 Prepare the Sample 72 5 1 2 Load the Sample 73 5 1 3 Load Probe in Tipholder 75 5 1 4 Install the Tipholder 77 5 2 Laser Alignmen...

Страница 5: ...pe 113 7 4 Withdrawing the Tip 115 7 5 Beyond Basics with Resonating Techniques 115 7 5 1 Subtleties of Cantilever Oscillation 115 7 5 2 Tuning the Cantilever Drive Frequency 117 7 5 3 Optimization of...

Страница 6: ...gments 146 Chapter 9 Scanning Tunneling Microscopy STM 147 9 1 STM Introduction 148 9 1 1 Overview of STM 148 9 1 2 STM Hardware 149 9 1 3 Sample Surface 150 9 1 4 Vibration isolation 150 9 2 Basic ST...

Страница 7: ...1 Obtaining a Good Force Curve 191 11 4 2 Helpful Suggestions 192 11 4 3 Advanced Techniques 194 11 4 4 Interpreting Force Curves 198 11 5 Force Calibration TappingMode 199 11 5 1 Force Plots 199 11 5...

Страница 8: ...Optical Interference 235 13 6 Advanced Topics 235 13 6 1 Lift Scan Height and Magnetic Imaging Resolution 235 13 6 2 Fine Tuning Interleave Controls 236 Chapter 14 Electric Force EFM Imaging 239 14 1...

Страница 9: ...ystem for Fine Tuning 294 15 7 2 Measure Horizontally at 440V Scan Size 294 15 7 3 Measure Vertically at 440V Scan Size 296 15 7 4 Measure Horizontally at 150V Scan Size 297 15 7 5 Measure Vertically...

Страница 10: ...nes across the image 320 15 12 3 Rings around features on the surface 321 15 12 4 Multiple or repeating patterns 322 15 12 5 Image goes white or black 323 15 13 Fluid Imaging Troubleshooting 323 15 13...

Страница 11: ...Rev B MultiMode SPM Instruction Manual 11 12 Blank...

Страница 12: ......

Страница 13: ...s Produce a Raster Scan Pattern 23 Figure 2 1h Various Tipholders utilized with the MultiMode SPM 24 Figure 2 1i Diamond Tip Mounted on Wire for Microhardness Testing and Lithography Work 25 Figure 2...

Страница 14: ...Using Retaining Springs 74 Figure 5 1d Tip Up Down Switch on the MultiMode SPM s Base 74 Figure 5 1e Silicon Nitride Probe Tip Installation 75 Figure 5 1f Underside Detail of Fluid Cell 76 Figure 5 1...

Страница 15: ...re 7 5d Suggested Range for Drive Frequency 117 Chapter 8 Fluid Operation 121 Figure 8 2a Fluid Cells 124 Figure 8 2b Load Probe into Fluid Cell 127 Figure 8 2c Fill the Fluid Cell with Liquid 128 Fig...

Страница 16: ...Scan Start and Scan Size 179 Figure 11 2c Tip Sample Interaction During a Force Plot 180 Figure 11 2d Anatomy of a Force Curve 181 Figure 11 3a Advanced Force Calibration Control Window Contact Mode A...

Страница 17: ...bottom view left to right 241 Figure 14 2a Comparison of attractive and repulsive forces to action of a taut spring attached to the tip 242 Figure 14 2b Diagram of Extender Electronics Modules in phas...

Страница 18: ...libration Maintenance Troubleshooting and Warranty 271 Figure 15 1a Scanner Crystal Voltage and Photodiode Voltage 277 Figure 15 1b Effect of Nonlinearity and Hysteresis 278 Figure 15 1c Veeco Silicon...

Страница 19: ...quency Operation 321 Figure 15 12c Dull or Dirty Tip 322 Figure 15 12d Double or Multiple Tips 322 Figure 15 16a MultiMode Scanner 329 Figure 15 16b Stabilizing screw for securing the vertical scanner...

Страница 20: ......

Страница 21: ...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 Microscope Specifications Section 1 3 Image Si...

Страница 22: ...tube As the scanner moves back and forth the sample moves with it allowing the probe to extract information from the sample surface much like a phonograph needle plays a vinyl record Because the size...

Страница 23: ...tal Instruments MultiMode SPM Introduction Rev B MultiMode SPM Installation Manual 3 Figure 1 1a MultiMode SPM System Components Control monitor Display monitor MultiMode SPM Keyboard NanoScope Contro...

Страница 24: ...licon TappingMode probes are prone to breakage if engaged too quickly or with too much force Ensure that engagement settings never exceed the limits of safety see Chapter 5 and never attempt to engage...

Страница 25: ...tzungen f hren k nnen This symbol identifies conditions or practices that involve potential electric shock hazard Ce symbole indique des conditions d emploi ou des actions comportant un risque de choc...

Страница 26: ...ut entretien ou r paration doit tre effectu par des personnes qualifi es et conscientes des dangers qui peuvent y tre associ s WARNUNG Service und Einstellarbeiten sollten nur von qualifizierten Perso...

Страница 27: ...Les tensions utilis es dans le syst me sont potentiellement dangeureuses et peuvent blesser les utilisateurs Avant toute intervention lectrique ne pas oublier de d brancher le syst me R serv au person...

Страница 28: ...ope MultiMode SPM est quip d une diode laser dont la puissance de sortie est inf rieure 1mW 670nm WARNUNG Das MultiMode SPM ist mit einem Halbleiterlaser ausger stet dessen Ausgangsleistung kleiner is...

Страница 29: ...iner les chantillons L exposition aux radiations non ionisantes de cette lampe est tr s inf rieure aux recommandations publi es par l American Conference of Governmental Industrial Hygienists ACGIH Le...

Страница 30: ...apable of exerting high forces A hand caught in the stage of a MultiMode SPM could be injured severely ATTENTION La platine des microscopes est automatis e dans les directions X Y et Z et est programm...

Страница 31: ...d einem Grund notwendig sein sollte ein Geh use mit elektrischen Bauteilen zu ffnen z B um eine Computer Karte auszutauschen schalten Sie das gesamte System ab und trennen Sie es von der Spannungsquel...

Страница 32: ...le Employer des tampons d alcool r guli rement pour d poussi rer la platine VORSICHT Tauschen Sie keine Proben aus w hrend sich das System im Betrieb befindet Der Probentisch sollte von Werkzeug ander...

Страница 33: ...ital feedback is governed by integral and proportional gain controls providing immediate response to scanning parameter changes The MultiMode can scan up to 200 m laterally in X and Y and 10 m vertica...

Страница 34: ...ess of surface features patented Force modulation is only one of several types of force imaging which are possible See Chapter 11 Lateral Force Microscopy LFM Measures frictional forces between the pr...

Страница 35: ...al to analog converters DACs Three DACs have 10V outputs and one DAC has a 12V and 220V outputs all four channels have 16 bit resolution In addition there are two 10V analog to digital converters ADCs...

Страница 36: ...Introduction to the Digital Instruments MultiMode SPM Microscope Specifications 16 MultiMode SPM Installation Manual Rev B...

Страница 37: ...eedback Section 2 2 A brief history of SPM control mechanisms Section 2 2 1 Feedback Gains Section 2 3 Proportional and Integral Gain An Analogy Section 2 3 1 Proportional Gain Section 2 3 2 Integral...

Страница 38: ...after Engagement Section 2 5 2 Terms and Abbreviations Section 2 6 2 1 Hardware This section provides a quick tour of the MultiMode SPM and its hardware The MultiMode SPM consists of seven major compo...

Страница 39: ...hown below see Figure 2 1b Figure 2 1b MultiMode SPM Head Laser adjustment knobs Photodiode Tipholder adjustment knob Scanner Shown A Scanner support ring Mode selector switch Motor control switch Bas...

Страница 40: ...tion depending on the operating mode In all modes the four elements combine to form the SUM signal The amplified differential signal between the top two elements and the two bottom elements provides a...

Страница 41: ...horter scanners e g type A offer smaller images down to the atomic scale Smaller scanners tend to be more noise free at acoustic frequencies because of their compact size and rigidity Larger scanner o...

Страница 42: ...igure 2 1f depicts the electrode configuration used on one type of scanner piezo tube Electrodes are oriented as shown when the MultiMode is viewed from the front AC signals applied to conductive area...

Страница 43: ...ted 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...

Страница 44: ...tilized with the MultiMode SPM CAUTION Some early model AFM tipholders may short out power supplies when used with MM SPMs If you suspect your tipholder is from an older AFM check with Veeco or your i...

Страница 45: ...es A potential is established so that electrons flow between the tip and sample A similar type of wire probe is used for lithography These often consist of ordinary tungsten STM tips and or a wire wit...

Страница 46: ...d by the sample s surface tension capillary properties that is trapped within a microscopic layer of condensed atmospheric water vapor on the sample surface This surface tension effect exerts consider...

Страница 47: ...electrical domains Note Both MFM and EFM may be conducted using the MM SPM alone however best results are obtained using a NanoScope III with an Basic Extender Module attached or a NanoScope IV Contr...

Страница 48: ...decreases respectively obeying an exponential relationship A diagram portraying the tunneling effect during STM is shown in Figure 2 2a In this example electron activity describes a zone several angst...

Страница 49: ...to a photodetector to obtain an optical lever capable of detecting even the smallest movements see Figure 2 2c This approach was then applied to SPMs A related method utilized interference to detect s...

Страница 50: ...urface as closely as possible without crashing into it This poses a dilemma to the balloonists how to tightly control the balloon s position relative to the ground Because the balloon will drift sligh...

Страница 51: ...e opens his valve at 10 liters per second if the balloon is 50 meters too low he opens his valve at 20 liters per second The proportional gain value serves as a multiplier such that at a proportional...

Страница 52: ...nally the third balloonist Larry employs yet another type of gain to ensure optimal tracking over the terrain LookAhead gain For our example Larry uses a map to anticipate the rise and fall of the ter...

Страница 53: ...ace surface features but not so much force that the tip is broken off or the surface damaged In the case of TappingMode it means holding the tapping force measured in terms of the oscillating probe s...

Страница 54: ...e next section discusses how signals are actually processed inside the NanoScope to render images 2 3 8 More about Feedback and Images Veeco s unique digital signal feedback architecture is described...

Страница 55: ...an be set by the operator to values between 0 and 1 0 these are not the values plugged into the equation This is a digital signal feedback process and the actual value multiplied varies between 0 and...

Страница 56: ...of 2 0 is not the same as 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 ty...

Страница 57: ...This allows a maximum of three Data types for any one sample For example a sample being imaged with contact AFM can show Height Deflection and Friction all at the same time 2 4 Control Parameters and...

Страница 58: ...in the fast scan X axis on display monitor direction Samples Lines Set the number of pixels displayed per line Line Set the number of lines scanned per frame Slow scan axis Starts and stops the slow...

Страница 59: ...se the gain settings at faster scan speeds and decrease the gains at slower scan speeds 2 4 4 Review of General Operating Concepts The AFM system is comprised of two main components 1 the scanner 2 th...

Страница 60: ...iode array A B 4 As the tip encounters a decline in the sample topology the tip drops This directs more of the beam onto the B portion of the photodiode array With the B photodiode receiving an increa...

Страница 61: ...photodiode array The diagram shows that the spot moves up more on A when the cantilever is pushed up The initial setup is to have the Vertical Deflection A B voltage about 2 3V more negative than the...

Страница 62: ...is number is multiplied times an accumulated average of A D readings This is the low frequency feedback control One of the easiest ways to set the gains properly is to view the input of the feedback l...

Страница 63: ...filtered into a DC voltage RMS Ampl The magnitude of the RMS amplitude is proportional to the amount of cantilever motion The feedback system compares the RMS amplitude to the setpoint voltage The two...

Страница 64: ...the cantilever is truly engaged with the sample surface A large Z piezo movement indicates that the cantilever is being damped by air trapped between the cantilever and sample surface not in contact...

Страница 65: ...hers The tip may stick and therefore be held to the sample surface if the RMS amplitude is too small The initial setup for TappingMode AFM is to 4 Tune the cantilever at its resonance a Select View Sw...

Страница 66: ...omputer processor used to control SPM feedback loop drive amplitude Amplitude of the signal used to oscillate a tip in TappingMode drive frequency Frequency of the signal used to oscillate a tip in Ta...

Страница 67: ...ncluding a substrate cantilever and tip proportional gain Correction applied in response to the error signal between setpoint force and actual force measured by the detector in direct proportion to th...

Страница 68: ......

Страница 69: ...and two monitors as described in this chapter Refer to support note MultiMode and Bioscope Facilities Requirements 013 311 000 for facilities requirements and environmental specifications 3 2 Componen...

Страница 70: ...Package of Contact Mode cantilevers silicon nitride type Package of TappingMode cantilevers single crystal silicon MultiMode SPM head see Figure 3 2a Figure 3 2a MultiMode SPM Head MultiMode SPM scann...

Страница 71: ...e microscope You will require a table of at least 76 x 152cm 30 x 60 size The table should be level of sturdy construction and located where it will not be vibrated or jarred by foot traffic It should...

Страница 72: ...ise Cabling 1 Before connecting cables review the following precautions CAUTION The NanoScope controller will overheat if the computer or controller ventilation holes are blocked or if the controller...

Страница 73: ...ment 3 Connect cables to the back of the NanoScope controller the power cable should be connected to the controller s receptacle on one side the controller to computer cable on the other Connect the c...

Страница 74: ...anner on the support ring with the scanner cap upright If the motorized scanner screw will not seat securely into the coupling on the base manually rotate the screw slightly until it aligns and seats...

Страница 75: ...spended from elastic bungee cords The mass should stretch the cords at least one foot but not so much that the cords reach their elastic limit The SPM should be placed on the large mass having a natur...

Страница 76: ...quence 1 Turn on the computer using the push button switch located on the front of the computer 2 Turn on the monitors 2 using the push button switches located on the front of the monitors 3 Turn on t...

Страница 77: ...lever Substrates The silicon cantilever substrates used in TappingMode can be removed from the wafer with the following procedure Note that the cantilevers are stored tip side up and that the silicon...

Страница 78: ...val of the substrates when needed Cover the container when not in use Figure 4 1a Silicon Cantilever Substrates in Wafer 4 Use the curved sharp pointed tweezers to remove the cantilever substrate from...

Страница 79: ...top of Figure 4 1b Front to back along the length of the lever the tip is asymmetric refer to lower right of Figure 4 1b Another factor affecting the interaction of the tip shape with the surface is t...

Страница 80: ...nsure that the area of measurement offers sufficient clearance so that other faces and edges of the tip and lever do not interfere with the measurement This method does not work well in small openings...

Страница 81: ...f the tip which exhibits symmetry Because of the approximate 17 half angle of the tip the line or space measurement is best done at the top of the line for simplification of the measurement artifacts...

Страница 82: ...d ridge near the highest point of the tip The exact length of the ridge is variable but rarely exceeds 0 5 m in total length It is inclined steeply so that for reasonably flat surfaces the highest poi...

Страница 83: ...play affecting the wall angle over shorter nominal 100nm step height measurements the shaped cusp at the end of the tip The shaped cusp at the end of the tip is formed to increase the sharpness of th...

Страница 84: ...ther as the cantilevers are between the strips All cantilevers on one side of both strips could break off if this occurs accidentally Figure 4 2a Silicon Nitride Cantilevers in a Wafer 3 Place the str...

Страница 85: ...antilevers on each end of the substrate Both 100 and 200 m length cantilevers with two different leg widths are provided When ready to use a cantilever substrate it may be desirable to remove the unus...

Страница 86: ...e values for spring constants and resonant frequencies Figure 4 2d Silicon Nitride Cantilevers Specifications and Tip Shape Because the silicon nitride probe tips have lower aspect ratios than single...

Страница 87: ...The oxide sharpened silicon nitride probes have a thermally grown silicon dioxide film deposited in the mold pit used to shape the nitride tip prior to silicon nitride film deposition The oxide has tw...

Страница 88: ......

Страница 89: ...f how to engage and withdraw the tip These procedures are common for most types of MultiMode SPM imaging Please refer to the following sections Initial Preparation for Contact AFM Imaging Section 5 1...

Страница 90: ...s from the back of the cantilever probe Note that the laser is powered when the SPM head is plugged into the microscope s support ring and the Mode switch is set to either AFM LFM or TM AFM TappingMod...

Страница 91: ...anch e sur l lectronique de contr le du microscope tant que la t te de mesure n est pas install e dans son support Il est imp ratif de faire tr s attention lorsque des chantillons tr s r fl chissants...

Страница 92: ...e should be placed on one of the 15mm diameter metal disks used for sample mounting The MultiMode SPM is provided with several steel sample disks that can be attached to the magnetic sample holder loc...

Страница 93: ...the sample puck with the calibration standard atop the scanner tube An internal magnet supplied with most units holds the puck down Figure 5 1b MultiMode Base with Scanner Mounted on Support Ring Rein...

Страница 94: ...adscrew at the rear of the unit to lift the head upward If you are using a standard three screw scanner the two forward screws will also have to be rotated to keep the head level while lifting Single...

Страница 95: ...de film side attached to the cantilever oriented up away from the substrate mount TappingMode The procedure for single crystal silicon probe tips is essentially the same as for contact AFM see above p...

Страница 96: ...roove Check that the probe s substrate is flush with the back of the groove and flat against one side this keeps the probe s cantilever oriented in the correct direction If identical probes are loaded...

Страница 97: ...ting the tipholder carefully over the sample Do not touch the sample with the tipholder 3 Press gently forward then lower the tipholder see Figure 5 1g Three precision ball mounts inside the head mate...

Страница 98: ...is step 2 While remaining in focus use the OMV stage screws to locate the red laser reflection spot Once located use the manual laser knobs on top of the head to move the laser onto the end of the can...

Страница 99: ...he surface below The X direction runs along the major axis of the substrate parallel to the length of the cantilever The right front laser control knob atop the optical head controls the laser beam mo...

Страница 100: ...edge and perpendicular to the cantilever until the beam crosses the cantilever and a shadow appears over the laser spot on the surface below The laser is now positioned over the cantilever see Point...

Страница 101: ...s and stop turning the knob The laser is now positioned at the edge of the substrate see Point 1 in Figure 5 2c Figure 5 2c Silicon Nitride Laser Alignment 4 Once the laser is positioned just off the...

Страница 102: ...pot disappears from the surface below 9 The laser is now on one of the two cantilevers To determine which cantilever the laser is on Note During this step do not adjust the back right laser knob or yo...

Страница 103: ...adjust the photodiode positioner to set the output signal to the desired value Figure 5 2d Signals Produced by the Photodetector are Optimized using the Head s Various Adjustments This adjustment is m...

Страница 104: ...k the NanoScope startup icon on the computer desktop You will see the NanoScope software window see Figure 5 3a which can span one or two monitor displays This large window will contain all the areas...

Страница 105: ...important control settings used for imaging 5 4 MultiMode SPM Voltage Meters A complete description of the signals coming into and out of the MultiMode SPM is available in Support Note 210 NanoScope...

Страница 106: ...minus the right segments With the mode switch toggled to TM AFM TappingMode it indicates the voltage difference A B that is the bottom segments minus the top segments The topmost digital meter 3 indi...

Страница 107: ...sections are included in this chapter Preparation Prior to Imaging Section 6 1 Adjust the Detector Offsets Section 6 1 1 Signal Settings Section 6 1 2 Adjust tip height above sample surface Section 6...

Страница 108: ...1a The detector adjustment screws are at the left side of the head Figure 6 1a Photodetector Mirror Adjustments Rear View Refer to Figure 6 1b For laser aligning screws atop the SPM head the right fr...

Страница 109: ...SiNi cantilevers or 0 5 and 1 0 Si cantilevers If performing LFM set Horiz Defl to 1 0 to 1 0V This is recommended for a 0 0V Setpoint Note Large offsets are not recommended between engage and disenga...

Страница 110: ...licon nitride tips on noncritical samples is to very slowly lower the tip using the adjustment screws until a sudden change is noted on the sum display of the MultiMode base Most silicon nitride canti...

Страница 111: ...he minus box in the upper left corner of the panel and click Show all items Figure 6 2a Select Show All Items 2 Ensure there is a X in the check box to the left of all parameters Note Those parameters...

Страница 112: ...Controls Panel 1 Select Panels Scan Set the Scan size as large as desired to 1 0 m and set the X and Y offsets to 0 0 2 Set the Scan angle to 0 0 Scan rate to 2 3Hz for single crystal silicon contact...

Страница 113: ...ntrols Panel Settings for Initial Setup Contact Mode Channel 1 2 and 3 Panel On the Channel 1 panel set Data type to Height see Figure 6 2e Set Data Scale to a reasonable value for the sample For exam...

Страница 114: ...nd the Deflection Setpoint to 0 0V Figure 6 2f Feedback Controls Panel Settings for Initial Setup Contact Mode Other Controls Panel 1 Using the mouse select Panels Other to display the Other Controls...

Страница 115: ...nfidence in use of the instrument is gained 6 3 1 Adjust Setpoint with Force Calibration The most accurate way to minimize the Setpoint value is by using Force Calibration Realtime View Force Mode Cal...

Страница 116: ...than the difference between the Z Center Position and the fully retracted position Procedure When you first enter force cal the graph will probably look like this The tip is being moved up and down a...

Страница 117: ...ip on the surface However this is not a stable way to image if the tip pops free of the surface the Setpoint must be increased to reattach the tip To minimize tip sample forces lower the Setpoint unti...

Страница 118: ...important as tip and cantilever technology continues to develop A clear understanding of the parameters in the Realtime control panel allows the user to tune the microscope to a wide variety of sample...

Страница 119: ...ller spring constants should be used on softer samples which will be destroyed by imaging with high contact forces 6 5 Optimization of Scanning Parameters Careful selection of the scan parameters is i...

Страница 120: ...ins are high as they should be for Height data the piezo height will change to keep the cantilever deflection nearly constant If the gains are low as they should be for topographical Deflection data t...

Страница 121: ...edure which is described in detail in the next portion of this section the contact force of the tip on the sample can be minimized This is especially important on soft materials such as biological sam...

Страница 122: ......

Страница 123: ...llowing sections are included in this chapter Basic Principle of TappingMode Section 7 1 Preparation Prior to Imaging Section 7 2 Switch to TappingMode Section 7 2 1 Show All Items Section 7 2 2 Check...

Страница 124: ...gMode Output Signal meter located on the front of the MultiMode base Figure 7 1b represents the same cantilever at the sample surface Although the piezo stack continues to excite the cantilever s subs...

Страница 125: ...uld glow green 7 2 2 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...

Страница 126: ...rameter Setting Scan Controls Scan Size 1 m X offset 0 00nm Y offset 0 00nm Scan angle 0 00 Scan rate 1 00Hz Number of samples 256 Slow scan axis Enabled Feedback Controls Integral gain 0 500 Proporti...

Страница 127: ...re 7 2c below Recall that RMS amplitude is an AC signal which does not have any real meaning until cantilever tuning is completed see Section 7 2 5 The laser spot will need to be approximately centere...

Страница 128: ...gnal amplitude yields low output voltage Vertical voltage difference high because laser signal falls on bottom half of photodetector only Well centered laser beam yields a vertical voltage difference...

Страница 129: ...mplitude A range of vibration frequencies will be applied to the cantilever to determine the frequency which produces the largest response the resonance frequency In most instances the resonance peak...

Страница 130: ...Tune button the computer and controller will do the rest setting such parameters as Setpoint and Drive amplitude automatically Table 7 2a Auto Tune Default Values At times it may be useful to tune th...

Страница 131: ...the Drive frequency parameter to a value near the center of the range of the resonance frequencies specified for the cantilever For example if the frequency range is specified as 240 420kHz select a...

Страница 132: ...rive Frequency can be decreased to the point where the vibrational amplitude reaches 90 of the maximum value It is often preferable to operate at a frequency lower than the resonant frequency due to s...

Страница 133: ...frequency After the microscope is engaged the RMS amplitude value displayed on the display monitor will match the Setpoint parameter specified in the Feedback Controls panel 7 3 Engaging The Microsco...

Страница 134: ...or followed by Engage You should now see a pre engage check If for any reason the engage aborts because the tip is still too far away from the surface use the coarse adjustment screws and or the Tip D...

Страница 135: ...very important to effective operation of the microscope It is also very important to understand similarities and differences between the force calibration mode of contact AFM and force calibration mod...

Страница 136: ...to the sample In general the solution to the problem is to decrease the scan rate and increase the feedback gains In some situations the feedback gains cannot be increased without causing piezo oscil...

Страница 137: ...determined that the microscope produces better data in TappingMode when the Drive frequency is set lower than the resonance peak of the cantilever The Drive frequency should be set such that it coinci...

Страница 138: ...an parameters required to collect good Height data are different than the optimal parameters for Amplitude data To collect Height data while tracking the sample surface with minimal change in the tip...

Страница 139: ...monitoring the Z Center position display in the Image Monitor When the tip is no longer interacting with the surface the Z Center position will move to the retracted limit Then slowly decrease the se...

Страница 140: ......

Страница 141: ...Cell with a Probe Section 8 2 4 Sample Mounting Section 8 2 5 Align the Laser Section 8 2 6 Adjust the Detector Offsets and Setpoint Contact Mode Section 8 2 7 Engage the Surface Section 8 2 8 Adjust...

Страница 142: ...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 Protein Binding Theory Section 8...

Страница 143: ...ve effects as the laser beam transits air fluid boundaries This chapter describes Contact Mode and TappingMode AFM operation of the MultiMode SPM in fluid including loading the probe into the probe ho...

Страница 144: ...or imaging samples in fluid using either TappingMode or Contact Mode These two fluid cells differ only in that the TappingMode fluid cell has a piezoelectric element that provides the probe oscillatio...

Страница 145: ...ents Contact Veeco for more information 8 2 1 Clean Fluid Cell and O ring To reduce contamination problems and to obtain high quality images clean the fluid cell and O ring if applicable as follows 1...

Страница 146: ...nless steel wire clip A tiny coil spring mounted on the top of the fluid cell holds the wire clip against the probe Load a probe into the fluid cell by performing the following procedure 1 Hold the fl...

Страница 147: ...Ton Epoxy or 5 Minute Epoxy For applications where contamination control is more critical use a more inert solvent free epoxy such as Master Bond EP21LV or EP21AR or a hot melt adhesive Note Follow th...

Страница 148: ...e fluid cell and does not overlap any edges of the sample If necessary use the XY translation knobs on the head to center the O ring Figure 8 2c Fill the Fluid Cell with Liquid 4 Verify the head is le...

Страница 149: ...Observe the fluid cell and probe through the viewing port using an optical microscope b Rapidly pull liquid through the cell with a syringe If sufficient force is applied the bubbles will be carried...

Страница 150: ...r bubbles form in the fluid cell and block laser light Reduce the chance of forming bubbles as follows Before installing the fluid cell into the head insert a syringe filled with liquid solution into...

Страница 151: ...rd micropipette or syringe 8 2 6 Align the Laser Use either of the techniques for aligning the laser on the probe see Chapter 5 Laser Alignment Section 5 2 The following considerations apply Refractio...

Страница 152: ...rtional gain Once engaged reduce the setpoint to minimize the tracking force 8 2 8 Engage the Surface 1 Using the Motor down switch and coarse adjustment screws if not using a vertical engage scanner...

Страница 153: ...contact forces in liquid than in air The optimal integral and proportional gains and scan rate may be different from air operation because the dynamics of the cantilever change in fluid 4 Set the two...

Страница 154: ...end of the cantilever portion of the probe 3 Center the photodiode to give a deflection signal near 0V 4 Set up the system for TappingMode operation Select Microscope Profile and choose a TappingMode...

Страница 155: ...appropriate for soft samples and typically results from a Drive Amplitude of 250 500mV A Drive Amplitude 1 0V generally works poorly with soft samples For rougher samples target 1 2V RMS amplitude Ex...

Страница 156: ...quality Both techniques are described in the next section It may be necessary to check the cantilever tune after engaging Select View Sweep Cantilever Tune When prompted for a Tip Offset enter 100 20...

Страница 157: ...w scan axis Select View Scope Mode and observe the agreement between the trace and retrace lines 2 Increase the setpoint in small increments until the probe pulls off the surface and the Z Center posi...

Страница 158: ...n necessary to dry the fluid cell with absorbent paper e g Kimwipe Degassing your imaging fluid prior to use in the AFM reduces bubble problems 8 4 3 Poor Image Quality Contaminated Tip Some types of...

Страница 159: ...the cantilever has remained stationary during a diffusion or settling period This may be due to the fact that some types of particulates are more attracted to the cantilever than to the substrate int...

Страница 160: ...er or outer walls of the circular groove in the fluid cell This allows the optical head to move laterally during engagement and helps in positioning the tip over the sample surface Choose the length o...

Страница 161: ...how to bind two different samples to a mica substrate Mica is commonly used because atomically flat substrates can be simply and inexpensively prepared In aqueous solutions the mica cleavage surface b...

Страница 162: ...at pH 6 This is shown schematically below in Figure 8 6a Figure 8 6a Proteins will typically bind to negatively charged mica when the pH is reduced below the protein s isoelectric point pI 8 6 2 Prote...

Страница 163: ...similar size samples This mixture should be drawn into a clean 1 cc syringe and capped Prepare another 5 cc syringe of straight buffer solution 3 Prepare the fluid cell for TappingMode in fluid operat...

Страница 164: ...ready for TappingMode imaging A good TappingMode image of lysozyme protein on mica is shown in Figure 8 6b Figure 8 6b TappingMode image of lysozyme in buffer solution using above sample preparation S...

Страница 165: ...tively charged mica in the presence of divalent counterions such as Ni 2 8 7 2 DNA Binding Procedure The following procedure is adapted from these sources Dunlap D D A Maggi M R Soria L Monaco 1997 Na...

Страница 166: ...trate with a piece of adhesive tape Place 30 l of the DNA solution in the center of mica disk The DNA will bind to the mica within 1 minute 4 Load prepared sample onto the AFM scanner and assemble the...

Страница 167: ...ration typically decreasing by a factor of two as the separation is increased 0 2nm The exponential relationship between the tip separation and the tunneling current makes the tunneling current an exc...

Страница 168: ...iezo based on the tunneling current error signal The STM operates in both constant height and constant current data modes depending on gain settings on the Feedback Controls panel The DSP always adjus...

Страница 169: ...t in the picoampere range Model MMSTMLC and an electrochemistry version Model MMSTMEC The low current converter head includes an in line electronics package Note The STM microscope heads were not desi...

Страница 170: ...e box filled with inert gas can improve the imaging Silicon oil or paraffin oil mineral oil also work well with some samples One minor problem involved with the use of oil is the increased difficulty...

Страница 171: ...Prepare the microscope 1 Insert a new STM probe in the STM converter head tipholder The tips come in a small plastic snap box filled with foam Grip the tip with tweezers near the sharp end and insert...

Страница 172: ...us box in the upper left corner of the panel and click Show all items Figure 9 2a Select Show All Items b Ensure there is a X in the check box to the left of all parameters Note Those parameters witho...

Страница 173: ...scanning tunneling spectroscopy STS modes of operation The variation of the tunneling current due to variations of the bias voltage or tip to sample separation can be tested and recorded at a single p...

Страница 174: ...ler spectroscopic plots This is generally not true for the I vs S plots Some general recommendations for acquiring spectroscopic plots are 1 Low settings for the Integral gain are preferred Since the...

Страница 175: ...erify that the 15 pin microconnector from the head is plugged into the microscope and the microscope is plugged into the controller Tip Never Engages If the tip never engages test for the following Di...

Страница 176: ...force By operating at in the G range for example and the tip sample distance increases enough to allow less destructive imaging of a variety of surfaces Picoampere level STM provides the opportunity t...

Страница 177: ...nics is 10 nA V This value must be changed to either 0 1 or 0 01nA V for operation of the low current head with gain factors of either 1010 and 1011 respectively To changes this value click on Realtim...

Страница 178: ...over and SPM base are electrically connected by the wire and that the can cover is in place The can cover acts as a Faraday shield 4 Please note that cables connecting the SPM base the Picoamp Boost B...

Страница 179: ...ltiMode s support ring using the micro D 15 pin connector cable Set switches on the picoamp booster to the desired current level and bandwidth 5 Before repowering the system double check all cable con...

Страница 180: ...me limitations which are absent in STM measurements with standard heads The bandwidth of the amplifier and consequently of feedback frequency response is substantially narrower than that used for stan...

Страница 181: ...rent STM Rev B MultiMode SPM Instruction Manual 161 Figure 9 5b STM current and height images of HOPG surface Scan size 6 0nm Itun 1 6pA Vbias 29mV Figure 9 5c STM current image of layered crystal RuC...

Страница 182: ...which may be damaged if exposed to sudden voltage spikes Spikes may be due to electrostatic discharge ESD or from external voltage sources Operators should always wear an anti static grounding wristb...

Страница 183: ...the new op amp from its protective package The op amp is stored in conductive foam and its leads have been preformed to fit the socket Be careful not to bend any of the leads Orient the op amp so that...

Страница 184: ...to secure 9 6 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 Variac...

Страница 185: ...lution with 2mm of the tips surface submerged More than 2mm will cause excessive foaming of the solution during etching and less than 2mm will result in tips that are too blunt 9 Connect the other out...

Страница 186: ......

Страница 187: ...ode it is relatively easy to use LFM to view and acquire lateral force data It is important to obtain a good image in Contact mode before measuring LFM data The NanoScope system will continue to run t...

Страница 188: ...lateral forces on the bottom of the color bar If the Line direction parameter is changed to Retrace the plus minus sign of the lateral force changes and low lateral force will be displayed on the top...

Страница 189: ...tact mode setpoint voltage will slightly adjust the gain of the lateral force signal By increasing the setpoint the contact force applied will increase and so will the frictional or torsional forces i...

Страница 190: ...is flexible enough to provide reasonable signal levels on samples with moderate friction If the signal exceeds 10 00V with the 200 m wide legged cantilever one of the stiffer 100 m cantilevers should...

Страница 191: ...10 2c Figure 10 2c Friction Data Number Trace or Retrace Tip Movement Level of Friction Photo Diode Voltage 1 trace slightly right slight slightly positive 2 severely right higher increases positive...

Страница 192: ...r substituting samples Also note that the laser spot position and changing the probe will also cause changes in the LFM measurement 10 2 6 Enhancing the LFM Data by Subtracting Two Images It is possib...

Страница 193: ...l be visible in the friction data if it s severe enough To distinguish real friction data from height artifacts remember that friction causes the cantilever to twist in the opposite direction as it tr...

Страница 194: ......

Страница 195: ...s Force Plots An Analogy Section 11 1 Force Calibration Mode Section 11 2 Example Force Plot Section 11 2 1 Contact AFM Force Plots Section 11 2 2 Force Calibration Control Panels and Menus Section 11...

Страница 196: ...rce Modulation Section 11 6 Introduction Section 11 6 1 Selecting a Force Modulation Tip Section 11 6 2 Operating Principle Section 11 6 3 Force Modulation Procedure Section 11 6 4 Notes About Artifac...

Страница 197: ...ndex of each magnet s power Similarly after attachment the researcher could pull each magnet away from the plate and measure the pulling force at regular intervals until the magnet breaks free The pul...

Страница 198: ...electric properties elastic modulus and chemical bonding strengths 11 2 Force Calibration Mode The Force Calibration command in the View Force Mode Calibrate menu allows you to quickly check the inter...

Страница 199: ...ple up and down the cantilever deflection signal from the photodiode is monitored The force curve a plot of the cantilever deflection signal as a function of voltage applied to the piezo tube shows on...

Страница 200: ...e lower spring constant of silicon nitride probes they are more sensitive to attractive and repulsive forces A force plot in contact AFM is shown below see also Figure 11 2c Figure 11 2c compares port...

Страница 201: ...ezo crystal which is plotted from left to right in yellow on the NanoScope display monitor 2 3 4 5 1 Piezo extension Piezo retraction Cantilever deflection 6 Up Down 1 2 5 6 Piezo extends tip descends...

Страница 202: ...is extremely sharp Since only a few nanometers of the tip actually touch the sample even minute forces are distributed over an exceedingly small area which add up quickly Many materials are easily de...

Страница 203: ...urve for Offline viewing Some parameters influence the operation of the microscope during imaging most of the menu parameters affect only Force Calibration mode Figure 11 3a Advanced Force Calibration...

Страница 204: ...e 11 2a displaces the piezo up and down in relation to the value of Z scan start Increasing the value of the Z scan start parameter moves the cantilever closer to the sample by extending the piezo tub...

Страница 205: ...ed force plots Display Mode This parameter defines the display as either the approach the retract or both Units This item selects the units either metric lengths or volts on the piezo that define the...

Страница 206: ...cantilever in nm It equals the inverse of the slope of the deflection versus Z piezo position line when the tip is in contact with a very hard stiff sample as shown in Figure 11 4c The NanoScope syst...

Страница 207: ...display monitor the Data Center must be 0 for that Channel Changing the Setpoint shifts the amplitude curve on the graph For example if the setpoint is at 3 0V the RMS amplitude axis of the graph wil...

Страница 208: ...ch of the two trigger types The plot series shown on the right side of Figure 11 3b utilizes a Relative trigger and maintains force at a constant level defined by the Trig threshold parameter The Rela...

Страница 209: ...alues Start Mode The Start Mode parameters are defined as follows Calibrate and Step Normal ramping no stepping unless you use Probe Approach Single or Approach Continuous Motor Step Uses the stepper...

Страница 210: ...er options in the Capture menu to change a capture filename and for continuous capture of all the force plots collected Probe Menu Commands These commands allow for highly controlled tip movement desi...

Страница 211: ...rve in Figure 11 2c However the force curve rarely looks typical immediately after invoking Force Calibration mode This section discusses general approach adjustments to improve force curves obtained...

Страница 212: ...e entire ramp will occur in the contact portion of the curve see Figure 11 4a between points 3 and 5 If this occurs increase the Ramp size and or decrease the Z scan start 11 4 2 Helpful Suggestions T...

Страница 213: ...in the center of the scanner range Because the Z axis leadscrew has some backlash it may be necessary to rotate the leadscrew several turns by clicking on the Tip Up or Tip Down buttons before obtain...

Страница 214: ...and line parallel to the contact portion of the force curve see Figure 11 4c Figure 11 4c Set the Sensitivity Parameter 5 The second click on the mouse causes the system to calculate the slope of the...

Страница 215: ...ponds to the zero deflection point and the tip of the retraction scan where the cantilever pulls off the sample surface VCSmin see Figure 11 4d The contact force is at its minimum when VCSmin is on th...

Страница 216: ...tact force F kd we can calculate the contact force from the sample plot above Let us assume for example that the spring constant of the cantilever is and that The plot above may be measured at the poi...

Страница 217: ...o the sample varies as features on the surface are encountered The contact force can be calculated by adding the deflection data from the image to before multiplying by the spring constant F k deflect...

Страница 218: ...elastic characteristics of samples 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...

Страница 219: ...urns off the X Y scan motion Next a triangular waveform is applied to the Z electrodes of the piezo tube resulting in the sample moving up and down relative to the oscillating tip The same Z axis piez...

Страница 220: ...ncreased bringing the tip about 50 nm closer to the surface Over the same interval the cantilever amplitude diminishes about 2 volts due to dampening effects Collecting a force plot on a hard sample a...

Страница 221: ...pon the hardness of the sample 11 5 2 Obtaining a Force Plot TappingMode When obtaining force plots in TappingMode set up scan parameters so that the reduction of amplitude is minimal approximately 25...

Страница 222: ...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 Set the Data type paramet...

Страница 223: ...ng the value of Z scan start until there is no flat portion on the left side of the curve Rapidly increasing the value of Z scan start is dangerous because the total oscillation amplitude of the canti...

Страница 224: ...nt of indentation For example a soft sample allows the tip to indent more deeply into the surface resulting in a very small deflection of the cantilever A hard sample allows less indentation with the...

Страница 225: ...For rubber and plastic samples Veeco recommends using 225 m long force modulation Model FESP silicon cantilevers For more delicate samples use 450 m long silicon cantilevers or silicon nitride cantil...

Страница 226: ...This section gives instructions for operating in Force Modulation mode 1 Choose the Force Modulation profile under Microscope Profile 2 Verify that the Microscope mode parameter in the Other Controls...

Страница 227: ...rting place each time you perform force modulation imaging however recheck the bimorph s resonant frequency in free air using Cantilever Tune each time you install a new cantilever a Use a FESP or TES...

Страница 228: ...lines until the selected peak is centered between the lines i Increase or decrease the zoom range by clicking the left mouse button j When the peak centers and the zoom width is adjusted double click...

Страница 229: ...he sample with the manual motor controls 10 Check the scan parameters Scan speed Scan size and Integral gain to verify they are reasonable for Contact Mode AFM imaging Also it may be desirable to read...

Страница 230: ...ontrast in the force modulation image Note It is possible to set the Drive amplitude too high If this occurs the Drive amplitude no longer increases the contrast in the amplitude image Instead the ove...

Страница 231: ...shifting the Drive Frequency slightly 1 3Hz below or above a resonant peak value may improve image contrast Operators are encouraged to experiment Edge Effects Sometimes force modulation images show...

Страница 232: ...le quantitative elasticity measurements between different samples and different cantilevers because the tip shapes may be different In general the force modulation technique is a qualitative tool for...

Страница 233: ...which varies according to the length and thickness of the cantilever You may perform TappingMode easily with either force modulation or TappingMode cantilevers but you may have difficulty with Contact...

Страница 234: ...the Channel 1 panel Data type parameter to Height 9 Set the Line direction to Retrace and enter an appropriate Data Scale value for your sample 10 Engage the tip on the surface and obtain a good Tapp...

Страница 235: ...e Once you minimize contrast enter a Lift scan height of 0 0nm and approach the surface 11 8 Force Volume Force volume imaging with the atomic force microscope AFM available with NanoScope software ve...

Страница 236: ......

Страница 237: ...iption Section 12 2 Lift Mode Description Section 12 3 Operation of Interleave Scanning Lift Mode Section 12 4 Use of LiftMode with TappingMode Section 12 5 Main Drive Amplitude and Frequency selectio...

Страница 238: ...bove the surface to perform far field measurements such as MFM and EFM By recording the cantilever deflection or resonance shifts caused by the magnetic or electric forces on the tip a magnetic force...

Страница 239: ...ack remains on during the Interleave pass with the values under Interleave Feedback Controls Setpoint Gains etc in effect In Lift mode the feedback is instead turned off and the tip lifted off the sur...

Страница 240: ...method When using LiftMode it is important that the gains and setpoint under Feedback Controls be adjusted to give a faithful image of the surface Because the height data is used in the lift pass to...

Страница 241: ...in the slow direction is halved 4 Display the interleave data by switching Scan line in the Channel panels to Interleave Lift scan height The lateral and vertical resolutions of the Lift data depend o...

Страница 242: ...an be set independently for the Interleave scan see below 12 5 2 Setpoint Selection When the main and interleave Drive amplitudes and Drive frequencies are equal bullets under Interleave Controls disa...

Страница 243: ...can 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 12 5 4 Amplitude Data Interpretatio...

Страница 244: ...ude can be large which for some applications may be beneficial The Lift scan height must be correspondingly large so that the tip does not strike the surface However the lateral resolution of far fiel...

Страница 245: ...r discusses the following topics Magnetic Force Imaging Theory Section 13 1 MFM Using Interleave Scanning and LiftMode Section 13 2 Procedure Section 13 2 1 Frequency Modulation Section 13 2 2 Install...

Страница 246: ...o be very small typically in the range 1 50Hz for cantilevers having a resonant frequency f0 100kHz These frequency shifts can be detected three ways phase detection which measures the cantilever s ph...

Страница 247: ...that the reader is familiar with the operation of TappingMode to obtain topographical images of a sample surface and has read the description of Interleave scanning in their manual LiftMode allows th...

Страница 248: ...senses force gradients due to the perpendicular component of the samples s stray field Tip magnetizers can be purchased from Veeco 2 Set up the AFM as usual for TappingMode operation In all Channel p...

Страница 249: ...se lag in degrees The Extender measurement however has slightly different nonlinear characteristics vs frequency The measurement technique allows optimal signal to noise ratios however absolute values...

Страница 250: ...ng Cantilever Tune and manually adjusting the Drive Amplitude parameter under Feedback Controls 5 Quit Cantilever Tune and return to Image Mode 6 Under Interleave Controls set the Lift start height to...

Страница 251: ...d Line direction to Retrace Note It is important that the Scan direction be set to Retrace for both the main and interleave scans If instead it is set instead to Trace a band may appear along the left...

Страница 252: ...ain to 50 for a Basic Extender and 0 6 for a Quadrex Extender or NanoScope IV As with the topography gains the scan can be optimized by increasing the gains to maximize feedback response but not so hi...

Страница 253: ...a NanoScope IIIA in the same way as the Basic Extender described above and has similar hardware requirements Quadrex operation requires NanoScope software version 5 12 or later 13 3 3 NanoScope IV The...

Страница 254: ...opriate Controller 4 Select the appropriate Extender Note This step is not necessary for NanoScope IV 5 Click the Ok button when complete 13 5 Troubleshooting Suggestions 13 5 1 MFM Image Verification...

Страница 255: ...ncy modulation 13 6 Advanced Topics 13 6 1 Lift Scan Height and Magnetic Imaging Resolution The most important parameter affecting imaging resolution is the Lift scan height The range of 10 200nm is m...

Страница 256: ...the main scan These parameters are enabled by clicking on the circular flag to the immediate left of the desired Interleave control toggling its state from off gray bullet to on green bullet When the...

Страница 257: ...ivity see Figure 13 2d With phase detection and frequency modulation changes in amplitude produce no change in contrast and results are thus more reproducible than with amplitude detection Note On som...

Страница 258: ...le distance in Liftmode sometimes with visible results in the magnetic image For this reason reproducible results are most easily obtained by using consistent setpoints Note that a lift scan height of...

Страница 259: ...igurations for systems without the Basic Extender Module Section 14 3 1 Jumper Configurations for systems with the Basic Extender Module Section 14 3 2 Electric Field Gradient Detection Procedures Sec...

Страница 260: ...roved results Amplitude detection has largely been superseded by frequency modulation and phase detection One of these hardware units is required for surface potential imaging and is strongly recommen...

Страница 261: ...d gradient large differences in topography can make it difficult to distinguish electric field variations In general the best samples for electric field gradient imaging are samples that have applied...

Страница 262: ...2 Electric Field Gradient Detection Theory Electric field gradient imaging is analogous to standard MFM except that gradients being sensed are due to electrostatic forces In this method the cantilever...

Страница 263: ...is sharp features on sample surfaces concentrate the local force gradient This happens on all roughness scales so the local force gradient will also vary in much the same way as does the surface topog...

Страница 264: ...pendent on the microscope being used and the measurements desired Section 14 3 1 provides jumper configuration instructions for basic microscope models operating without the Basic Extender Module in f...

Страница 265: ...ould appear as shown in Figure 14 3b whereas jumper systems with the Basic Extender option should appear as in Figure 14 3g If the microscope is to be used for EFM imaging in cases where voltage is ap...

Страница 266: ...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 fee...

Страница 267: ...ode SPM Instruction Manual 247 Figure 14 3c Jumper configuration for application of voltage to tip for systems without the Basic Extender Module Sample Tip Analog 2 Ground Analog 2 Gain Select Auxilia...

Страница 268: ...e input attenuation must be disabled for the duration of the EFM experiments To do this select di Microscope Select Edit Advanced to display the Equipment dialog box Set Analog 2 to User defined Retur...

Страница 269: ...uration for applying external voltage to tip for systems without the Basic Extender Module A current limiting resistor e g 10 100M should be placed in series with the external voltage supply as shown...

Страница 270: ...g external voltage to sample for systems without the Basic Extender Module A current limiting resistor e g 10 100 M should be placed in series with the external voltage supply as shown to protect the...

Страница 271: ...he 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 b...

Страница 272: ...ntrol the attenuation 1x or 8x of the main feedback signal This application of EFM imaging uses the Analog 2 signal for EFM data Therefore input attenuation must be disabled for the duration of the EF...

Страница 273: ...erefore input attenuation must be disabled for the duration of the EFM experiments To do this select di Microscope Select Edit Advanced to display the Equipment dialog box Set Analog 2 to User defined...

Страница 274: ...information Figure 14 3j Jumper configuration for applying external voltage to tip for systems with the Basic Extender Module A current limiting resistor e g 10 100M should be placed in series with t...

Страница 275: ...applying external voltage to sample for systems with the Basic Extender Module A current limiting resistor e g 10 100M should be placed in series with the external voltage supply as shown to protect...

Страница 276: ...n Back of Basic Extender Module Table 14 4a Basic Extender Module Toggle Switch Settings Note The toggle switch combination of Surface Potential ON and Analog2 ON is not recommended and can produce er...

Страница 277: ...e Detection is only available when the Basic Extender Module has been correctly configured into the system In the Cantilever Tune window set Start frequency and End frequency to appropriate values for...

Страница 278: ...hannel 1 image Data type to Phase and choose Retrace for the scan Line direction on both Channel 1 and 2 images Switch Interleave mode to Enable to start LiftMode Set the Channel 1 Scan line to Interl...

Страница 279: ...in detail in Chapter 13 of the appropriate product instruction manual 14 4 2 Amplitude Detection With Basic Extender Module To set up for Amplitude Detection field gradient imaging on systems with the...

Страница 280: ...shown in Figure 14 4d When using Amplitude Detection optical interference may sometimes appear in the lift magnetic force image when imaging highly reflective samples Optical interference appears as e...

Страница 281: ...interleaved that is they are each measured one line at a time with both images displayed on the screen simultaneously A block diagram of the surface potential measurement system is shown in Figure 14...

Страница 282: ...tial on the sample Vsample The Extender determines the local surface potential by adjusting the dc voltage on the tip Vtip until the oscillation amplitude becomes zero At this point the tip voltage wi...

Страница 283: ...xternal power supply to the MultiMode ground or the AFM chassis 1 Power down the NanoScope controller and turn off all peripherals Unplug the NanoScope power cable from the microscope s electronic box...

Страница 284: ...cuits connect electrical leads directly to pads For normal operation the sample chuck is held at ground be certain to carefully any electrical connections from the sample chuck Figure 14 6b Applying V...

Страница 285: ...der pins Heat may cause damage and or make jumpering the pins difficult The sample should be electrically connected directly to the chuck or a standard sample puck using conductive epoxy or silver pai...

Страница 286: ...ocate the cantilever resonant peak Remember however that the Extender box has been reconfigured so that the phase detection circuitry now acts as a lock in amplifier Any procedures that are normally u...

Страница 287: ...height can be readjusted later Set the drive phase to 90 This compensates for mechanical lay in the cantilever as it responds to the oscillating electric field 11 Switch Interleave mode to Enable to...

Страница 288: ...serving the change in the phase signal Find the point where the phase is minimized For MESPs SCM PITs and OSCM PTs this value should be near 0 For TESPs this value is normally around 45 Once the minim...

Страница 289: ...this problem Once oscillation stops the FM gains may be increased for improved performance In Scope Mode if the Potential signal is perfectly flat and shows no noise even with a small Z range the fee...

Страница 290: ......

Страница 291: ...ically this chapter includes SPM Calibration Overview Section 15 1 Theory Behind Calibration Section 15 1 1 Calibration References Section 15 1 2 Calibration Setup Section 15 2 Check Scanner Parameter...

Страница 292: ...15 7 5 Change Scan angle and Repeat Calibration Routines Section 15 7 6 Calibrating Z Section 15 8 Engage Section 15 8 1 Capture and Correct an Image Section 15 8 2 Measure Vertical Features Section 1...

Страница 293: ...rrect Section 15 11 8 Z Center Position goes out of range Section 15 11 9 Poor image quality Section 15 11 10 Force Calibration command does not seem to work Section 15 11 11 Image features appear was...

Страница 294: ...nner If the SPM is engaged disengage from the sample by clicking on the Withdraw icon several times Unplug and remove the SPM head from the microscope Remove the sample then unplug and remove the old...

Страница 295: ...using one or both of the following methods Capture Calibration and Autocalibration A built in software routine automatically controls the scanner while capturing a series of data files The data files...

Страница 296: ...ically to a voltage Because of slight variations in the orientation and size of the piezoelectric granular structure polarity material thickness etc each scanner has a unique sensitivity or a ratio of...

Страница 297: ...is measured in terms of lateral displacement for a given voltage nm V In addition the NanoScope software employs various derating and coupling parameters to model scanners nonlinear characteristics B...

Страница 298: ...increasing voltage is not the same as their response to decreasing voltage That is piezo materials exhibit memory which causes the scanner to behave differently as voltages recede toward zero The gra...

Страница 299: ...road range of scanner movements Because scanner sensitivities vary according to how much voltage is applied to them the reference must be thoroughly scanned at a variety of sizes and angles The user t...

Страница 300: ...mensions Atomic scale calibrations are generally carried out with mica or graphite which exhibit very regular atomic lattices Calibration references serve as the primary tool by which SPMs are calibra...

Страница 301: ...re 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 Alig...

Страница 302: ...ity image maximum Scan size 440V The Scan rate should be set to a value of 2 44Hz and the Number of samples parameter should be set at 256 With the sample engaged check the scanning line relative to t...

Страница 303: ...Note In Figure 15 3a pits align with the vertical slow axis but skew with the horizontal fast axis The angle should be measured with the vertex near the center of the image and the vertices in the up...

Страница 304: ...to optimize the linearity correction parameters for individual scanners As discussed previously linearity correction is especially important for long range scanners 15 4 1 Adjust Mag0 and Arg 1 Select...

Страница 305: ...on is set to Trace 7 Move and size the zoom box until the beginning third of the scan s features are exactly aligned with the zoom box Note The beginning third of the scan is the standard for judging...

Страница 306: ...ced across the Fast axis Figure 15 4b Fast Scan Linearization Arg 5 After setting Fast mag0 and Fast arg insert the values for Slow mag0 and Slow arg These values serve as close starting points before...

Страница 307: ...ginning and ending of the scan then check the center 3 If the features in the center are too large reduce the Slow arg value If the features in the center are too small increase the Slow arg value 4 A...

Страница 308: ...is usually adequate however if more precision is desired use the following fine adjustment techniques to adjust Fast mag1 1 Use the same procedure for adjusting Fast mag0 2 As before set the Zoom box...

Страница 309: ...in the NanoScope software using the Capture Calibration command The basic calibration procedure using version 5 XX software and a 10 m calibration reference see Figure 15 1c is described in this sect...

Страница 310: ...es see Figure 15 5b Figure 15 5b Capture Control Dialog Box Note The capture status will begin at skip 2 The program skips the current scan plus one more before capturing an image for later calibratio...

Страница 311: ...ne File Browse or click on Browse to review all Capture Calibration files 11 Verify that all calibration images contain features spanning the full width and height of the image frame see the right ima...

Страница 312: ...llowing 1 Select one of the desired captured calibration images in the Capture directory Select Offline Utility Autocalibration The control monitor will display the X Y Piezo Calibration dialog box Ve...

Страница 313: ...the distance covered by the white line drawn on the image If a 10 m reference is being employed like portions of features are spaced 10 m apart e g between bottom edges left sides etc Note Measure fe...

Страница 314: ...Scan Controls panel to the maximum value 440V 2 Verify that the Scan angle is set at 0 00 degrees 3 Mount a calibration reference into the SPM and begin imaging This may consist of a generic e g 10 m...

Страница 315: ...wo fine tuning is required go to Step 3 below If the displayed distance agrees with the known distance skip to Section 15 7 3 3 Based upon the results in Step 2 perform the following calculation Divid...

Страница 316: ...t 440V Scan Size 1 Return to the image of the calibration reference Clear the horizontal line drawn in Section 15 7 2 click the right mouse button or click Clear After waiting for at least three full...

Страница 317: ...then use the mouse to draw a horizontal line between them For example on a 10 micron silicon reference draw the line from the left side of one pit to the left side of another pit as far away as possi...

Страница 318: ...dely spaced features on the sample image of known separation then use the mouse to draw a vertical line between them For example on a 10 m silicon reference draw the line from the top edge of one pit...

Страница 319: ...ater accuracy you must select an appropriate calibration standard and or a metrology head employed with a Veeco MultiMode microscope Note Refer to the label on your calibration reference sample to ver...

Страница 320: ...se to zero use the Realtime Motor Tip Up and Tip Down buttons to adjust 15 8 2 Capture and Correct an Image 1 Capture an image by selecting Capture in the Realtime menu or click on the CAPTURE icon Wh...

Страница 321: ...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 perform...

Страница 322: ...minent peaks These peaks correspond to two elevations on the surface the bottom of the pit and the top surface There should be a line cursor on each peak 4 If the two peaks do not appear in the displa...

Страница 323: ...pth indicated in Depth analysis by the Peak to Peak value 3 Multiply this quotient by the Z sensitivity value in the Z Calibration dialog box and replace the former Z sensitivity value with the new re...

Страница 324: ...the calibration standard with a 100V Z Center Position 4 Record the measured depth If the depth measured by the extended piezo is off by more than two percent continue on to Step 5 Step 8 Note The mea...

Страница 325: ...rn the X Y stage adjustment screws on the AFM microscope Do not turn more than a 1 2 turn in each direction 3 When the scanner tip encounters a pit in the Scope trace diagram it will display a step in...

Страница 326: ...omic scale imaging The Z axis is calibrated in the normal way using a silicon calibration reference as described in Section 15 8 above 15 9 1 Prepare Sample Perform the calibration with either highly...

Страница 327: ...ise due to thermal drift If difficulty is experienced obtaining an image Withdraw and try a different site on the surface then Engage again Many users find it easiest to obtain good image measurements...

Страница 328: ...rage distance displays on the bottom right corner of the display monitor s status bar If the measurements vary by more than 2 percent from the dimensions shown above make a correction 6 Correction of...

Страница 329: ...calibrating the Z axis 15 10 Quick Guide to Piezo Tube Calibration 15 10 1 Linearize Scanner This calibration is not necessary during routine maintenance 1 Engage in Contact AFM with these settings S...

Страница 330: ...Tune the X Y Scanner Note You can use Capture Calibrate and Autocalibrate in place of Fine Tune Sensitivity 1 Engage the microscope and scan at 440V 0 Scan angle 2 Adjust the X Fast sens until the fa...

Страница 331: ...Change the Z scan sens until the depth measures correctly actual depth measured depth Z Sens correct Z sens 7 Select Realtime Motor Tip Up to move the Z Center position to 100V 5V 8 Capture an image...

Страница 332: ...0a Calibration Recommended Parameters 019 020 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 90...

Страница 333: ...rge steps or topography These effects can cause scattered light to be reflected onto the photodiode assembly along with the reflected beam from the back of the cantilever The scattered light causes ch...

Страница 334: ...r beam using a magnifier or slip of paper Click on the Withdraw command to remove the cantilever from the surface and recheck alignment with the magnifier or paper method see Chapter 5 When satisfied...

Страница 335: ...ontamination The tip will effectively become longer and this will cause the feedback loop to raise the tip to keep the same tracking force The contamination can come off of the tip which will cause an...

Страница 336: ...itivity parameter must be calculated as described in Section 15 8 or height data will be inaccurate When acquiring deflection data for height measurements gains must be set low to reduce movement of t...

Страница 337: ...ple If image quality is poor with distorted shapes and low contrast try adjusting the gains first then optimize the scan direction to take advantage of the best tip shape to improve image quality Vary...

Страница 338: ...e Cal command will not provide a meaningful display when first invoked Z scan start and Scan size as well as Setpoint affect the position and shape of the curve and will probably require adjustment to...

Страница 339: ...ers produce strange resonance curves so the first thing to do when an unusual resonance curve occurs is to clean the groove on the cantilever mount and reseat the cantilever If this does not improve t...

Страница 340: ...age on the display monitor Increase the Setpoint voltage until the Z Center Position voltage jumps to the fully retracted position 2 Note the current Setpoint voltage value This value is just slightly...

Страница 341: ...beneath water see Figure 15 12b This is caused by operating with a drive frequency too close to cantilever resonance Use the arrow keys to increment the drive frequency a little lower Do this while w...

Страница 342: ...tapping force on the surface or because the tip encountered a feature too high to successfully traverse If this occurs change the tip Note Operating with a smaller difference between the RMS voltage...

Страница 343: ...lled Further suggestions for solving this problem consist of the following Use the fluid cell without the O ring as described in Chapter 7 of this manual This technique works best on hydrophobic surfa...

Страница 344: ...g the supplied O ring it is best to place the O ring on the sample before placing the head on the scanner 15 14 Adjustment Screw Maintenance Procedure This section covers maintenance procedures for ad...

Страница 345: ...ic rotational limp i e alternatively easy then difficult to turn Faint crunching or grinding noises when rotated Microscope cannot engage sample surface i e motor is unable to rotate rear adjustment s...

Страница 346: ...it may bind against the threaded insert If the bound adjustment screw is forcefully rotated the screw will almost always destroy the brass insert threaded inserts may become cross threaded or strippe...

Страница 347: ...Lubricate Apply a very fine layer of lubricant to each adjustment screw Lubricant may consist of high vacuum grease optical coupling grease or equivalent Screws should exhibit a slight sheen and no m...

Страница 348: ...noScope controller 4 screws 3 Using a screwdriver press the slot in the fuse holder and rotate the fuse a 1 4 turn counter clockwise 4 Gently pull the fuse away from the board 5 Carefully remove the r...

Страница 349: ...ature the following Completely motorized tip sample engage Fully vertical engage head does not tilt Easy to locate tip on desired scan area 0 5 m lateral repeatability on subsequent engages Accommodat...

Страница 350: ...ring c Secure the scanner to the ring using one of two screws supplied see Figure 15 16b Figure 15 16b Stabilizing screw for securing the vertical scanner to the support ring MultiMode AFM screw left...

Страница 351: ...rovided below 15 16 2 Select scanner Select Realtime Microscope Scanner and choose the appropriate scanner After highlighting the newly copied scanner file then click on the panel s Ok button to exit...

Страница 352: ...anner is adjusted to its maximum tube height the leadscrew may disengage from the motor coupling on the MultiMode base This is a built in feature to prevent motor burn out To reengage the leadscrew re...

Страница 353: ...ecial order shall carry the above warranties with respect to material and workmanship but shall be specifically excluded from any other warranties express or implied including those related to perform...

Страница 354: ...lied and constitutes fulfillment of all of Veeco s liabilities to the purchaser Veeco does not warrant that the system can be used for any particular purpose other than that covered by the applicable...

Страница 355: ...les of 39 314 Contact Force 101 203 Contact Veeco Technical Publications 333 D Data type force modulation 209 Data type 99 101 118 119 231 LFM 168 Date type 232 Deflection 99 DNA imaging with TappingM...

Страница 356: ...can height 221 principles of 219 L Laser safety hazard 5 symbol 5 Laser Hazard symbol 5 Lateral Force Microscopy 167 173 Left Image 93 LFM principles of 167 scan angle 169 Lift scan height 220 221 230...

Страница 357: ...ns 10 precautions 6 12 sample safeguards 12 symbols 5 Safety Hazards attention 5 electrical 5 general operator safety 6 12 laser 5 lifting 5 mechanical crushing 5 Safety Precautions 6 12 Sample precau...

Страница 358: ...op explained 37 drift during fluid imaging 323 loss of Z center position 316 no engagement 313 314 poor image lines 315 320 poor image repeating images 322 poor image rings around features 321 poor im...

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