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1. The other important fact 1s the light intensity delivered by the source In order to have a clear and sharp view of the sample with the optical microscope you will have to adjust the light intensity delivered by the light source Besides 1t 1s useful not to have the optics totally vertical Instead you can try to place 1t in a similar way as shown in the next picture AFM head Fig 3 12 Itis advisable not to place the optics completely parallel to the laser of the AFM head 44 e Finally you can try changing the camera settings in the software in order to see the best image as possible with the best resolution Fig 3 13 Example of image taken with the optical microscope system Gold electrodes with metallic contacts 45 Chapter 4 First Use of the System STARTING WSxM 1 Before turning on Dulcinea electronics put the sample on the magnetic support of the piezo or non magnetic sample holder in MFM case 2 Make sure the height of the micrometer support screws 1s enough to hold the head above the sample without crashing the cantilever Place the cantilever chip in the cantilever holder and then insert the cantilever holder into the head see Chapter 2 3 Turn Dulcinea electronics on and run WSxM You will find the following options Re DA LY ER Fig 4 1 4 Select the Data Acquisition option by pressing PA Then the following icons will appear 5 Check that the parameters of the system you are goi
2. To do it by software take a look to the Z values on the top of the Channels Values Menu see Fig 4 29 This value is telling you the Z off in nm Just add that number to your Z off and the green bar will be centered As a general rule anytime you want to center it add the value you see in the Channels Values Menu to the current value placed in the Zoff dialog 62 For example if Z value 200 nm and you have a Zoff 300 nm to center the green bar you should place Zoff 100 nm APPROACH IN CONTACT MODE 20 In the Control Menu set the initial scan Frequency to 1 Hz and the Number of Points to 256 The Set Point value will be used by the feedback system to control the tip sample distance In Contact Mode the feedback channel is the Normal Force CH1 you can see 1t in the Feedback Menu Fig 4 30 The system keeps 1t constant comparing the Set Point value with the Normal Force value from CH1 you can see it in the Channels Values Menu Fig 4 29 changing the tip sample distance to keep the Normal Force constant To set an initial value for the Set Point before approaching check the Normal Force value channel 1 CH1 in the Channels Values Menu see Fig 4 29 Since you have tuned the photodiode in the Photodiode Menu making the red and the green crosses coincide the Normal Force and the Lateral Force should be 0 Place the initial Set Point around 0 2 0 4 V as shown in the next figure Size nm 0 Freq Hz f
3. 4 43 Fwd Bck signals after doing what has been said in Fig 4 42 Fig 4 44 the system is in the proper feedback range obtained after waiting a few seconds after Fig 4 43 IMPORTANT Once you have performed the Motor Move Approach then some Step Approaches and also some Set Point increments if the system is not in the proper feedback range you can enter a scan size for example 2000 3000 nm and continue with the Approach Instead of seeing a sudden flattening of the Fwd Bck traces when the system achieves the proper range you will see topography traces which also can be used to indicate when the tip is close enough to the sample NOTE You can change the Set Point value directly typing its value but you can do it also using the arrows in the dialog box You will get large value changes clicking the arrow To produce smaller changes click the arrow while pressing SHIFT or CRTL to even smaller ones This is important even more when you are very close to the right position between tip and sample in order to properly achieve the Set Point value Note that all the parameters in WSxM can be changed in this way Once you have the tip close to the sample with Fwd Bck traces equal and flat it could happen that the green bar which tells you how much elongated is your piezo scanner is not centered If the green bar is far away from the center and the Z Gain is 15 or 10 we do recommend stepping the motor in the Approach Menu After sc
4. cover the AFM head with the glass cover 53 APPROACH IN DYNAMIC MODE 11 Select the Dynamic Menu by pressing Then the following window will appear LMC Patametete Miremara Frequency Hz 11 1000 al Massi Frequency Hz 150000 Frequency Hz foo E Delay au 150 DB Amplitude v as 4 Phase legit 270 Filer out Hz exo Gan Gsm ry 2 Gan cut amphlude PS gt Gain cut Y phase 2 Default Faks Info Haranta Frequency Hel Undefined Frequency Hz Undefined Component yt Lndehaed Y Component HT Undelmed Ampitude Vh Undeinad Linear Scar Adranced Hiiragi Fig 4 24 12 Check that the parameter values are the proper ones for your cantilever and if not change them Usually cantilever manufacturers specify the applications for each cantilever While soft cantilevers lt 1 N m are commonly used in Contact mode in some cases they can also be used in Dynamic modes The most important parameters are the Minimum and Maximum Frequencies the Amplitude of the voltage applied to the cantilever driving piezo and the Delay Briefly the delay 1s the number of times the amplitude of the cantilever at the resonant frequency X component and its phase Y component are measured to obtain an average value Y ou should know roughly the value of the resonance frequency of the cantilever you are using In this way you can fit the limits of the frequency searching interval Mini
5. 3 0 25 0 2 0 15 0 1 0 05 Amplitude V OF Ta 10000 1 5e 4 2e4 2 5e4 3e4 3 5e4 4e4 45e4 Frequency Hz Fig 4 56 A typical resonance frequency peak and the mechanical resonances of the liquid cell system Note the range of the Frequency in the figure going from 10 kHz to around 500 kHz Total Amplitude V Total Amplitude V 0 0 l l l 6 5e 4 Te 4 7 5e4 Se 4 Frequency Hz Fig 4 57 a Resonance freq peak in air l 8 5e 4 J4 9 504 TA A 2604 2884 3e4 324 3de4 Frequency Hz Fig 4 57 b Resonance freq peak in water F 81 kHz F 28 kHz Final Remarks for operation in liquid environment Values for the feedback parameters Proportional and Integral in liquid environment are usually different from those used when operating in air usually smaller Anytime you introduce liquid thermal drift is usually strong You will need to allow some time for the system to stabilize Jumping Mode allows an accurate control of the force applied to the sample Dynamic Mode does not 80 A few relevant references I L Ivanovska P J de Pablo B Ibarra G Sgalari F C MacKintosh J L Carrascosa C F Schmidt and G J L Wuite PNAS 101 7600 7605 2004 F Moreno Herrero P J de Pablo R Fern ndez S nchez J Colchero J G mez Herrero and A M Bar Applied Physics Letters 81 2620 262
6. an anti vibration table e You will receive the digital camera placed on the top of the optics You can change its orientation by loosening the coupling part the one on the top of the optics fixed with three allen screws Plug the camera into a USB port in the CPU The software is already installed The CD with the drivers and the software is provided separately To access the different sections of the digital camera software you must click on the shortcut Fig 3 3 Icon for the optical microscope software that you have in the desktop on your computer 37 The next screen you should see looks like NA OZNTZA Click here to start the digital camera video visualization B Media E ES My Photo H My oo ge My Voice Fig 3 4 Then the live video will start and you will see the next options Resolution A Video device settings Video Device Creative WebCam Pro ex Video while live video Video Size 640 x 480 Format Source Captured photo Capture settings resolution Photo size 1024 x 7D0 Save Photo in My Alburn Save Video in My Alburn Save automatically Photo capture Video capture B Settings Fig 3 5 Live video If you click the Settings icon Settings hkl General Image Capture Video Capture ay This settings page allows you to set the general properties of the application Here you can sele
7. bottom corner Scan Phase and Linear Scan Minimum frequency Enter the lower limit for the frequency range over which the resonance frequency is going to be searched Maximum frequency Enter the higher limit for the frequency range over which the resonance frequency is going to be searched Frequency WSxM will display in this box the value of the active frequency Delay The number of times the amplitude of the cantilever at the resonant frequency X component and its phase Y component values are measured to obtain an average value Setting the delay properly insures you obtain an accurate value for the amplitude square root of the square of these values of the signal from the dynamic board Amplitude Amplitude of the excitation applied by the dynamic board to the dither piezo in the cantilever holder If the tip were free oscillating without feedback increasing this amplitude would result in a larger oscillation of the cantilever However because of the feedback attempts to maintain a given set point amplitude increasing the oscillation causes the tip to approach the sample since the feedback attempts to keep the amplitude constant Phase Phase difference between the oscillation of the cantilever and the signal applied to the dither piezo 90 Filter out Upper limit for the low pass filter used to eliminate high frequency noise that may be present in the signal going to the dynamic board A typical value is ab
8. button In principle it is not necessary to switch off Dynamic Mode if it is ON or to turn off the laser WSxM will automatically perform these tasks A shutdown message will appear on the front screen of Dulcinea Then you can turn Dulcinea off 74 MEASUREMENTS IN A LIQUID ENVIRONMENT Scanning Probe measurements under liquids are performed using a specially designed liquid cell that is shown schematically in Fig 4 50 The instructions below assume you already have a basic knowledge of the Nanotec Electronica SPM Hardware as described in this manual laser support beam magnet support magnet sapphir xl Ndoa liquid meniscus NINN liquid pool Figure 4 50 A schematic diagram of the liquid cell not to scale Pay Attention When using the liquid cell no liquid must enter into the piezo scanner If this happens switch off the system and contact us To use the liquid cell follow the instructions below e Put the desired sample into the plastic liquid pool You can fix it firmly with grease Fixing the sample to the pool is critical to avoid movements while measuring which in the case of a liquid environment could be especially important e Clean the sapphire window of the cantilever holder as required Chloroform or a cleaner for screen filters gives the best results A clean window is critical to achieve high sensitivity 75 Fig 4 51 Place a small drop of vacuum grease onto the cantileve
9. getting to the end in order to avoid damage to the piezo e Connect the piezo scanner to the chassis through the LEMO connectors see Fig 2 9 making sure that you align the red points in each of them Listen for a click when connecting them together The high voltage signal to the piezo scanner is supplied through this connector 14 The next step is to check that the motor is properly connected see Fig 2 10 MOLEX CONNECTOR 2 PINS Fig 2 10 Motor connection e Make sure you connect the MOLEX connector as shown in Fig 2 10 In case it is connected in the opposite way the motor will approach when you want to withdraw 15 Now it is time to place the head To do that follow the next diagram LEMO CONNECTOR FGG 1B BP LEMO CONNECTOR HCG 1B Fig 2 11 AFM head assembly e You have to place the head onto the three micrometer screws at the motor base matching them with the appropriate holes in the head see Fig 2 11 You can also place it at the parking head see Fig 2 1 e Connect the head to the chassis through the LEMO connectors see Fig 2 11 making sure that you align the red points and that you hear a click when connecting them 16 At this point once you have assembled all the mechanical components Now you must connect the mechanical system to Dulcinea DB 37 CONNECTOR Metallic cover Fig 2 12 Dulcinea connection Note the screws in the DB37 connector do not screw into the c
10. in the Control Menu This will force the dashed square to change its size To change the angle of the scanned area use Angle in Control Menu One of the sides of the square has a different color This feature is used as a reference line that allows you to determine the angle you are scanning with 0 is when this side is at the bottom To change the portion of area over which you are scanning click once on the point where you want to go If you have clicked on the wrong point double click on any point to return to the original point 95 These actions will be displayed in a yellow square showing the change made but they will not be updated until you click Update in the Control Menu The change of position will be shown on the Control Menu automatically displaying the new X Y Offset values When you click Update a progress bar will show you the progress of the Offset movement and 1t will also be represented as the movement of the yellow square When all the parameters have been updated the computer will continue measuring 96 Appendix C Jumping Mode Non contact sampling sometimes the properties of the sample need to be measured when the tip 1s far from the sample To do this you can make the tip stop approaching for a while at a determined distance from the sample while you perform a measurement You can select the available Air 1 e Non contact Channels on Viewer Options when working in Jumping Mode Distance tip sam
11. of all of the measurements taken as the representative data point In most cases it 1s better to use this mode when acquiring data Secure use this button to withdraw the tip when needed This is done by retracting the Z piezo preventing the tip from crashing into the sample during times when the stability of the AFM head 1s being disturbed While withdrawal is being done WSxM will show a notice box in the screen To elongate the Z piezo after the changes have been done click on Update or click on Secure again There are two bars on the right of the box The green bar on the right monitors the Z piezo elongation Since the best position for scanning is the midway position a red mark is used to indicate this optimal spot The red bar on the left monitors the error achieved when measuring This error represents the difference between the Set Point and the actual value of the normal force The lower this bar is the more accurate scan you get There may be many contributions to this error The error scale number is the one in the box below the two bars It represents the scale at which the error bar is shown You can change its value either by entering it in the box or by using the back and forth buttons on the right of the box Using them you will get a change in one unit if the number is higher than two and a 10 change for the other values no matter whether the CTRL or SHIFT keys are pressed or not Some of the parameters discussed abov
12. off determine the Z offset on the sample Angle determines the angle in the X Y plane at which the sample will be scanned The effect of changing the angle can be viewed using the Position Window Bias use it to set the voltage between the tip and the sample if you have a conducting tip The voltage will be applied to the tip Set Point determines the reference normal force between the tip and the sample or the reference tunnel current for STM Depending on the mode that is being used the Set Point has negative or positive values When working in Dynamic Mode it is negative and the closer to zero it 1s the closer the tip is to the sample In Contact Mode the value should be positive and the bigger it is the harder the tip is pressing against the sample Usually the Set Point is displayed in volts or nA for STM however when Force Calibration has been applied it may also be displayed in nN or in nm If you enter a value too high WSxM will warn you and will set an allowed Set Point value Signal Gain determines the gain for the incoming signal to Dulcinea This Gain should not be modified unless for some reason the incoming signal is extremely low There are only four allowed values for this box 0 654 1 5 and 9 808 Z Gain determine the factor by which the Z signal will be amplified in Dulcinea There are six allowed values for this box 0 06 0 29 1 5 10 and 15 Use a value that suits the Z scale of the sample If you
13. parameter you can change 1s Motor Voltage V which controls the motor speed It is usual to use a value of 6 8 V approximately 19 Once the parameters are set press Approach in the Move option If Z Gain in the Control Menu is not 15 the maximum one WSxM will suggest you to change it to this value to let the piezo move all the Z range if necessary The screw will move until the tip is in range Then the motor will stop and the piezo will extend retract you can notice this by looking at the vertical green bar shown in the Control menu and in the Approach Menu which represents the Z piezo displacement If the piezo is fully extended the green bar will be at its maximum If the piezo is fully retracted then the green bar will disappear You will also notice 1t because there will be no topography Fwd Bck traces 60 e How to know when the tip is close enough to the sample When the system 1s working properly the Fwd Bck traces should be similar At the beggining before scanning Size 0 display the Topo view in oscilloscope mode with a viewing scale of 2 nm and Filter Offset This means that the tip 1s close enough to the sample and the system has the proper feedback settings Just after the whole approaching process since the sample is not moving and the tip is just oscillating above the sample there is no topography variation This is why the Fwd Bck traces should be flat and constant equal to cero If the Fwd Bck
14. parameters The calibration parameters shown in Piezo Settings vary depending on the piezoelectric scanner Scan Options ms I Feedback Control E ACA Scan Blas Logaryt mic Feedback On 7 y PA ak J Retrace Ho F la 4 EE _ Variable Speed el s Delay rs hs o Til mak Pro Safety Z Litt mE CITS No Found percent Andas Chi Curen al Fig 5 7 Feedback and Scan parameters 16 17 18 19 Using the Viewer Options set the channels as follows Channel 0 Current nA F plane Channel 1 Topography nm F plane Channel 2 Current nA F plane Channel 3 Topography nm oscilloscope mode FB offset Channel 4 Current nA oscilloscope mode FB offset Set the manual z piezo position knob to 5 0 V offset This knob is on the front of Dulcinea to the right of the LCD screen If you want to enable the manual positioning of the z piezo check the z manual icon 2 to the left of Z off set in the Control Menu to make the manual position knob active Be careful this knob overrides the current tip distance feedback system If the z manual icon is not checked this knob will not be active and the Zoffset will be changed only by software Now we are ready to approach the tip Open again the Approach Menu and go to Advanced AE Ane Approach Motor Time ma Walt Time ma Approach feedback F Approach feedback Motor Voltage MI Motor Step Time ms pproach c
15. so follow the instructions given in steps 23 and 24 HOW TO ACQUIRE IMAGES 30 Once tip and sample are close enough and in the proper feedback range start scanning To do this assign a value to the Size in the Control Menu the resulting image will be a square with the size you just specified equal to the length of one side It is advisable to start the scanning with the maximum Zgain to allow the piezo to move over its entire range to avoid crashes Enter a Size that is not too large around 2000 4000 nm by entering the proper parameters to obtain a reliable image before increasing the scanning Size It is very important to fit the value of XY Gain in the Control Menu to get the best resolution possible Place the minimum XY Gain that WSxM allows Note that you can also use automatic XY Gain 1f you are using a Develop version of WSxM then WSxM will do the work for you You can learn more about the meaning of XY Gain as well as the other Control parameters by reading Appendix B You must understand that the Z Gain is also very important Once you are scanning and obtaining images it is very important to work with a Z Gain as low as possible to get the best possible resolution The Z values are monitored using an indicator bar in the Channels Values Menu see Fig 4 29 The width of this indicator bar displays the range of the data along the Z axis If the indicator bar width is very small compared to the range of the scanner yo
16. the spatial coordinates To measure distances between two points click on one point and extend the line to the other one The status bar will also display the modulus of the vector between the two points length of the line between the two points and if you draw more than one line the angle between both lines will also be shown 94 4 il Center Use it to redefine the center of the portion of the sample being scanned On the Status bar two boxes will show you the matrix coordinate equivalent to pixel coordinates and the real coordinate equivalent to the spatial coordinates where the cursor 1s positioned Click on this icon and then click on the point you want to define as the new center of the image WSxM will re center the image You can also redefine a new center using the features of the Position Window To open the Position Window press ma in the toolbar The following graph will appear Position Fig B 1 Use this window to visualize and change the area over which you are scanning Use it also to check the orientation of your sample and the size of the area you are scanning The dashed square represents the maximum area that can be scanned given the selected XY Gain on the Control Menu whereas the blue square represents the area that is actually being scanned To change the size of the scanned area use Size in the Control Menu To change the maximum area that can be scanned use XY Gain
17. 2 2002 F Moreno Herrero J Colchero J G mez Herrero and A M Bar Phys Rev E 69 031915 2004 Pay Attention No liquid must enter into the piezo scanner If this happens switch off the system and contact us 31 Chapter 5 Tutorial on HOPG Use of Air STM Head Highly Ordered Pirolityc Graphite HOPG is a laminar compound lts surface 1s extremely inert and flat Using Scanning Tunnelling Microscopy 1t 1s simple to obtain atomic resolved images of this surface In this tutorial the process to obtain those images 1s described 1 Stick the HOPG sample to a thin plate of a ferromagnetic material A conducting epoxy is the best choice of adhesive If conducing epoxy is not available use a regular epoxy to stick the sample and contact the edge of the sample with the metal plate using silver paint 2 Stick a piece of Scotch tape to the surface of the HOPG sample Pull the tape to obtain a fresh surface This cleaving process usually leaves graphite flakes on the surface using the edges of the tape remove as many flakes as possible 3 Place the sample on the scanning piezo With a multimeter check the resistance between the sample and ground the external side of any BNC in the electronic is grounded The resistance must be a few ohms otherwise the silver paint is not getting a good electrical contact 4 Cuta 1 5 cm platinum iridium wire Fig 5 1 Air STM Head 82 5 Take the STM head and partially uns
18. 23 Cantilever holder ready for use 22 8 To remove the cantilever chip and replace it with a new one the process 1s similar to that already described but in reverse order An explanatory diagram 1s provided below Using the CEB fork stretch the rubber Once the rubber strip has been lifted strip unclamping the cantilever chip push it back holding the CEB fork on from the cantilever holder the CEB base with the CEB stop CEB fork CEB sto CEB base Diagram showing the CEB fork position held against the CEB base by the CEB stop after pushing back the rubber strip Remove the old cantilever chip and insert a new one If you do not insert a new cantilever chip If you insert a new cantilever chip Release the rubber strip to its natural Clamp the cantilever chip with the position rubber strip remove the CEB fork 23 INSTRUCTIONS FOR CHANGING THE RUBBER STRIP To change the rubber strip of the cantilever holder you will need a screwdriver and tweezers 1 Using the screwdriver loosen the four screws in the cantilever holder to release the top part blue one as shown in Fig 2 24 Notice that it is not necessary to unscrew them entirely Fig 2 24 Releasing the top part of the cantilever holder 2 You will now have two separate parts as shown in Fig 2 25 Fig 2 25 Removing the top part of the cantilever holder 24 3 Using the tweezers remove one side of the rubber strip holding 1t wit
19. 4e 4 8 11e 4 Frequency Hz Frequency Hz Fig 4 25a Fig 4 25b NOTE The optimal Total Amplitude value for the cantilever to oscillate will depend on many parameters including sample roughness and the selected cantilever If the sample is very flat you can usually use a small value but if it is rough you should use larger ones typical values range from 0 2 V to 5 V It is advisable to use the lowest input Amplitude possible to avoid instabilities To implement this you can adjust the Gain in located in the dynamic window see Appendix A Once you have found the cantilever s resonance frequency check that it 1s similar to the expected value and exit the Dynamic Menu Once Dynamic Menu is closed while measuring you can see and change the Dynamic parameters by pressing the button see Fig 4 26 Dynamic Settings 55 Gain ir eal Gain out 3 200 Gain out ef Amplitude joo Frequency Hz 294092 97 Phase Deg hoa fs Filter cut Hz 30824 p rg Scan Senesitrity KHz 0 048 Advanced Update Fig 4 26 14 In the Control Menu see Fig 4 27 This menu is usually already opened button insert the scanning Frequency Freq Hz and the Number of Points in one scan line Size nm lo alo Freg Hz io af Paints jse 2 af x off mfo af Y ofta fo af E Z otf nmo af Angle IS alo HY Bias mv Jo o Set Point Ef 0 88 af Signal Gain af Z Ga
20. 6nmx6nm From LNM Laboratorio de Nuevas Microscopias Departmento Fisica de la Materia Condensada UAM 99 Centro Empresarial Euronova 3 Ronda de Poniente 2 Edificio 2 14 Planta Oficina A Tres Cantos E 28760 Madrid SPAIN Phone number 34 918 043 347 Fax 34 918 043 348 e Mail nanotec nanotec es 100
21. Amplitude reduction to Range 9 gt Advanced 2 Piezo position Move Step Withdraw Withdraw Approach Approach Fig 4 33 The Approach Menu controls the motor There are two options Move and Step Move the screw rotates in a continuous movement until it is in range The parameter to control the Move Approach option is Amplitude reduction to range You will change this value depending on the cantilever you are using and how careful you want to be while approaching For example with cantilever_1 it could be OK to use a value of 10 approximately while with cantilever_2 which is more fragile than the other and usually has longer tips a value of 5 should be OK For the latter case since the tip is longer the cantilever is further away from the sample while approaching so the electrostatic interaction 1s lower and almost all the amplitude reduction is due to the tip sample interaction As the amplitude will reduce constantly during the approach due to the long range cantilever sample interaction the Amplitude reduction to range tells the system to look for a sudden change of the Amplitude equal to that selected in this field Step the screw rotates in a discrete way with short displacements for each step The parameter to control the Step option is Motor Step Time ms It is usual to use a value of 100 ms when tip and sample are still far and 50 ms when they are closer The other
22. WS NANOTEC SPM user manual Dear friend Thank you very much for selecting Nanotec Electronica SPM products The Nanotec team hopes that you will enjoy them and we are sure they will satisfy all your SPM measurement requirements In the following pages you will find instructions for the different parts of the system Please read them carefully paying special attention to the safety recommendations included for optimal results Also you will find with your system a WSxM 2 0 software manual with explanations about the different software options Please note that at http www nanotec es you can subscribe to NanotecForum a discussion forum to which all Nanotec Electronica SPM users are welcome Best regards The Nanotec Electronica Team Centro Empresarial Euronova 3 Ronda de Poniente 2 Edificio 2 14 Planta Oficina A Tres Cantos E 28760 Madrid SPAIN Phone number 34 918 043 347 Fax 34 918 043 348 e Mail nanotec nanotec es Instruction Manual Index Chapter 1 Dulcinea electronics DS TO eater p 4 Sal AIG UNC IONS it ces es ee ele p 6 l stallation MSU MCU ONS propor p 7 so A ee eer nee ene meee meee eres p 7 Chapter 2 AFM Hardware PR A o nn II cea ueaesmcehetacenpeseeeeenes p 9 Installation nStrUCUON Saint ria p 14 Ao A O E ces sane ie nee mee eennteerens p 18 Instructions for changing the rubber StrIp oocccccccoccnononnnnnnnnnnonnnnnnnnnnnnnns p 24 O e UN EEE eene p 34 Chapter 3 Opt
23. ad or to any extra intermediate electronics using the cable s for this purpose Now you can power on the electronics and the computer and start WSxM software to control it 4 Use of the electronics WSxM software 1s used to control the Dulcinea electronics First start the WSxM software WSxM 3 0 or later required When starting the Data Acquisition part of the software File Acquisition Acquisition Start WSxM will recognize that the Dulcinea electronics is connected and will display the serial number and software version Dulcinea electronics will also respond to this communication and will update messages on the screen If the Secure button is pressed WSxM software will detect it and prevent you from beginning the Data Acquisition before unpressing the Secure button This button 1s generating an extra offset to the Z piezo voltage that will not allow you to work properly With the acquisition started you can use the button besides the Z Off parameter Z Offset in the Control menu to enable manual handling of the Z Offset to the piezo You can use the Scanning Dulcinea outputs menu for selecting the signals you want to monitor In some cases these signals can be used to interface third party systems Chapter 2 AFM Hardware 1 Description The Nanotec AFM mechanical system can be divided into two main parts the chassis and the head In the following images a general view of the different components is provided Labels pro
24. al adjustment of the photodiode Screw 4 for coarse horizontal adjustment of the photodiode Fig 4 13 7 Adjust the photodiode position in such a way that the laser spot reflected from the cantilever is centered on the photodiode To do this click on Tune Photodiode lk A window to help you align the photodiode will appear Two screws control the coarse movement vertical movement screws 3 and 3 and horizontal movement screw 4 The other two screws horizontal movement screw 5 and vertical movement screw 6 control fine movement The coarse movement allows you to position the whole photodiode holder with your hands see Fig 4 15 The blue bar labeled Optical Power must be as high as possible and the red cross must be centered inside the blue square Note that when having some optical power the green cross appears when the red cross 1s inside the blue square see Fig 4 16 The green cross is a magnified view of the red cross With the fine movement screws you can precisely adjust the photodiode making the red and the green crosses coincide by using screws 5 and 6 as shown in Fig 4 17 After this process the blue bar in the Photodiode Menu which corresponds to the total Optical Power should be as high as possible usually at least over the mid point and the crosses in the photodiode window should be centered Do not worry if you do not have the maximum Optical Power It depends on the laser adjustment the optics in t
25. anning for a while you may notice that the green bar has drifted from its centered position You do not have to make Step approaches to re center the green bar Instead you can use the Z offset Zoff in the Control Menu There are two options by software or by hardware To do it by hardware first of all make sure the knob on the front panel of Dulcinea 1s in the middle range 5 Then enable the icon wE beside Zoff and you will be able to center the green bar by turning the knob To do it by software take a look at the Z values listed on the top of the Channels Values Menu see Fig 4 29 This value indicates the Z offset in nm Just add that number to your Z Offset and the green bar will be centered As a 67 general rule anytime you want to center 1t add the value you can see in the Z values in the Channels Values Menu to the current value placed in the Zoff For example 1f Z value 200 nm and you have a Zoff 300 nm to center the green bar you should enter Zoff 100 nm APPROACH IN JUMPING MODE 25 In the Control Menu set the Number of Points to 256 In Jumping Mode the Z piezo scanner jumps at each point in the image essentially performing an FZ curve For this reason the Frequency in the Control Menu is not relevant Other parameters control the movement as we will see later and that is why working in Jumping Mode the Frequency in the Control Menu is disabled In Jumping Mode the feedback channel is the N
26. aphy variation This is why Fwd Bck traces should be flat and constant If the Fwd Bck traces are not similar you must make further adjustments There are a number of possibilities to consider A If the piezo is fully extended maximum vertical green bar shown in the Control Menu and in the Approach Menu You will also notice it because there will be no topography in the Fwd Bck traces continue to approach the tip toward the sample For this e Use the Step option in the Approach Menu giving the necessary steps to center the green bar 1t 1s advisable to get 1t centered while measuring because then the Z piezo will be in terms to move in the maximum range in both directions up and down e Increase the Set Point value until getting Fwd Bck traces the same reaching this state with a sudden flattening of them If the Z piezo becomes fully extended again before the traces flattening repeat the above process When the Fwd Bck traces become equal center the green bar by making step approaches When the green bar 1s centered close the Approach Menu B If the piezo is not fully extended there are two possibilities e Fwd Bck traces are flat and constant having reached this state by the appearance of a sudden onset of flattening The system is in the proper feedback range Center the green bar by making step approaches withdrawals When the green bar 1s centered close the Approach Menu e Fwd Bck signals are not flat and constant i
27. art 3 in the diagram to the base of the stand part 2 using the three allen screws parts 1 and their respective pressure washers e Place the arm of the stand the long black cylinder part 3 a into the orifice of the grey block that comes with the leg part 3 b This grey support block is fixed to the leg by means of one of the two screws equipped with black knobs that come separately This screw is the one that enables the horizontal movement of the optical microscope when it comes over the AFM head Make sure the part that supports the grey block to the leg black cylindrical part with a manual screw part 3 c is very well fixed because it is the part that supports all the weight of the optical microscope The other manual screw with a black knob is used to fix the arm to the grey block In order to balance the microscope system it is recommended to position the grey block in the middle of the arm as shown in Fig 3 1 e At the end of the arm unscrew the part called part 7 in the diagram with its washer part 6 and insert the final part of the stand part 5 replacing parts 6 and 7 to their initial position e Place the optics part 4 in the diagram into part 5 of the stand leaving the connection for the optical fiber on the right side e Connect the light source with the optical microscope by means of the optical fiber leaving the light source and the AFM chassis on different tables usually the AFM chassis is placed on
28. cantilever oscillation CH15 you can see it in the Feedback Menu Fig 4 30 The system keeps it constant by comparing the Set Point value with the value from CH15 you can see it in the Channels Values Menu Fig 4 29 changing the tip sample distance to keep the Amplitude constant To set an initial value for the Set Point before approaching check the Amplitude value channel 15 CH15 in the Channels Values Menu see Fig 4 29 When you approach to the sample the oscillation amplitude will decrease due to the tip sample interactions but also due to the cantilever sample interactions the latter is a long range interaction with a low variation with the distance For some cantilevers this interaction can produce false stopping points when approaching That is why you have to put an initial Set Point value lower than the amplitude shown in CH15 this implies a Set Point value closer to 0 than that found in CH15 57 e If you are using a cantilever similar to cantilever_ 1 the initial Set Point value should be around 1 2 the initial value in CH15 e If you are using a cantilever similar to cantilever 2 the initial Set Point value should be 3 4 the initial value in CH15 16 In the Feedback Menu see Fig 4 30 This menu is usually already opened button 4 Insert feedback parameters P and I Proportional Integral As a general rule take P 20 and I 10 as initial values Main Linear Feedback On P Smooth input 2 mont
29. crew the two screws that hold the triangular plates tip holder The screws must be loosened just a little bit in order to allow the platinum iridium wire to be inserted between both plates Fig 5 2 Loosen the top plate 6 Insert the wire leaving about 7 mm protruding out of the plates and tighten the SCTCWS Fig 5 3 Insert the tip wire 83 7 Cut the very end of the protruding wire at an angle of about 45 8 Raise the three micrometer screws so that when the STM head is placed on these screws the tip will not touch the sample The front two micrometer screws must be moved by hand the third screw is moved using the motor but can also be moved by hand To move the third scew using the motor open WSxM go to Data Acquisition DA and then click on 66 Once in the Data Acquisition Menu ha click on 2 and the Approach Menu will appear approach o Motor Voltage Gi Motor Step Time ms Bo aie Approach curent n Mo A Advanced Pieza position hove Shep Mtra Withdraw Approach Approach Fig 5 4 Approach menu 9 Click on Withdraw to move the motor until the micrometer shaft lengths are long enough to hold the head and tip above the sample 84 10 Place the STM head on top of the 3 micrometer screws and clamp the head to 11 12 13 14 15 the base using the retaining springs Make sure that the tip is not touching the sample By using the 2 manual approach scr
30. crews 1 and 2 in Fig 4 13 You will know when the laser beam is falling on the cantilever because the typical diffraction pattern will appear 47 To align the laser and to tune the photodiode place the SPM Head on the Head Parking supports see Fig 4 6 Head Parking Parking scre n Fig 4 6 Hand held screen 48 Now follow these steps e Place the laser beam on the chip which contains the cantilever you will see just a diffuse red light on the parking screen and the shadow of the chip cantilever Fig 4 8 The approximate dimensions of the cantilever chip s shadow are 2 x 3 mm e Then move the laser beam along the chip parallel to the cantilever use screw 1 see Fig 4 13 until arriving and surpassing the edge of the chip You will know when you surpass it because you will see a clear spot under the cantilever holder Fig 4 9 it is advisable to place a paper screen at the base of the Head Parking as shown in Fig 4 6 e Once the laser beam is beside the edge of the chip move it perpendicular to the cantilever with screw 2 searching for the cantilever until you find its diffraction pattern e To make the final adjustment you can use a little piece of paper Hand held screen placed as shown in Fig 4 7 to visualize the diffraction pattern Move the laser perpendicular to the cantilever length use screw 2 until it is positioned in the middle of the cantilever diffraction pattern with maxim
31. croscope head and place it in the right position above the optical cube of the AFM head Until you are familiar with the optical system practice with it away from the AFM system to avoid damage if you do something wrong e When installing and operating with the optical system make sure it does not touch any part of the AFM head Position it in such a way that the optical microscope can be moved removed above the AFM head properly While looking for the optimum focus position take special care that any part of the optical microscope does not touch the laser or its cable as it could misalign it 4 Use of the optical microscope Once the optical microscope 1s installed the first thing you must do is to turn on the light source and to start the software of the digital camera in the CPU e Then you have to place the optical microscope objective above the optic cube of the AFM head e Probably you will not see anything at first You have to look for the right vertical distance between the optical microscope and the AFM head in order to have the sample in focus The correct focus is about 2 3 cm above the head You also will have to take into account the zoom of the microscope It is advisable to begin with the lowest zoom as possible and then once you have an image change it as required See figure 3 11 42 USB cable Camera NNITAR Focus Fine Adjustment Optical Fiber Fig 3 11 Optics in the optical microscope 43
32. ct the default Album settings directory to store files where Default directory to store media files images will be saved if you C Media check the box Save automatically see Fig 3 5 When the video file in the album is comupted You have to select the C Always delete destination and create there a Always ignore new album see next image Fig 3 7 Carcel Amb Fig 3 6 Settings You have to click in see Fig 3 4 The next menu will appear Add Alburn f Create new album This option vall allow you to crate a new folder to add i into the album library Use existing folder as album This option vell allow you to add an existing folder mto the albur library Note The folder name will be used as the album name Fig 3 7 Add Album 39 Brightness Image Modes Black and White In this menu you can change all the pase E t usual camera control parameters Gamma z da Flip Vertical brightness contrast in order to Saturation a g Backlight improve the image which is being given by the digital camera The other possibility is to select Use an existing folder as album Add Album A ES C Create new album This option will allow youto create a new tolder to add it into the album librar Use existing folder as album This option will allow you to add an existing folder into the album library Note The folder name will be used as the album name Alb
33. do not know the scale as is customary for the first time the sample is scanned use the highest value and modify it as needed when scanning XY Gain determine the factor by which the X and Y signals will be amplified in Dulcinea As for Z Gain there are six allowed values for this box 0 06 0 29 1 5 10 and 15 Use the minimum value that allows you to scan over the desired area of the sample The maximum area allowed on the Position window is determined by this value Please observe that in order to obtain large scanning areas with a piezo high voltages have to be applied 92 The buttons in the low part of the box are used as follows Up Middle and Down click on them when you want the tip to move to the upper middle or bottom part of an image while you are scanning They are useful when modifications to the scan parameters have been done while the tip is scanning Y Scan this button 1s pressed by default It makes the tip scan in the Y direction If this button 1s not pressed the scanning will be only done in the X direction If the Y scan 1s deactivated the scan will be done over the same line on the X direction every time This feature can be useful when a particular feature on the substrate is being investigated as a function of time Smooth During normal operation at every scanned point several measurements are acquired but only one is selected to represent a data point If this option is selected WSxM will use an average
34. dotted arrow in Fig 2 39 You have to place the head side screw see continuous arrow in Fig 2 39 in the retaining spring hole as shown in the next image Fig 2 40 After placing one of the Retaining Springs do the same with the other spring NOTE While you place the first retaining spring with one hand with the other one hold the head If you are using a MFM head you have to be more careful In this case the head has no magnets so it is not magnetically fixed to the chassis When placing the Retaining Springs while you place the first one with one hand always hold the head with your other hand and after placing this first retaining spring do not let go of the head until placing the other one 33 3 Safety instructions e If you have an optical table remember to slacken the optical table brakes in order to move the optical table with the micrometer screws e Bevery careful while placing or changing the piezoelectric scanner It is one of the most fragile parts of the system e Never try to disassemble any mechanical hardware or electronic component of the system without previous authorization from the manufacturer or authorized representative e The micrometric motor approach screw in the chassis see Fig 2 2 can also be moved by hand after pushing down the motor If you move it in this way make sure that after the movement the white plastic coupling piece 1s perfectly aligned otherwise the micrometer screw will
35. e are set by default by WSxM Usually the default values are the ones you entered when you last used the program To change a parameter just type a new value into the dialog box associated with the parameter Any modifications entered into a dialog box are highlighted with a yellow background until they are implemented IMPORTANT To make any modifications effective you have to click on the Update button located in the lower part of the box The changes can be implemented by pressing Intro immediately after the change is entered Otherwise the background will remain yellow and no changes will be made to the existing scanning parameters 93 The updating will take an amount of time required for the tip to finish scanning the current line However if you change the Set Point or the Bias value by using the cursor the update will occur automatically as soon as the tip finishes scanning the current line In this case the Update button does not need to be clicked Quality representation buttons Use an appropriate quality representation when changing the size of your windows ea Low quality representation WSxM plots one fourth of the data points on each line Medium quality representation WSxM plots one half of the data points on each line High quality representation WSxM plots every data point on each line Repaint Often the scale of an image is changed in the course of a scan All scan lines after the change w
36. ease check that the cantilever is fully inside the liquid and the liquid is touching the sapphire window If this is not the case either you need to approach the tip to the sample or you need to add more liquid into the pool Fig 4 53 Liquid capillary marked by red arrow Due to the presence of the liquid the position of the laser on the cantilever needs to be readjusted in the normal direction along the cantilever You should realign it while you check on the Hand held screen until you have again the 2 spots Adjust the photodiode position as in standard SFM Contact mode Proceed in a similar way as in standard Contact Mode Jumping mode Proceed in a similar way as in standard Jumping Mode However please realize that the adhesion force between tip and sample is much smaller because there 1s no capillary T1 and or liquid neck formed between the tip and the sample Therefore there 1s no capillary contribution to the adhesion force see Fig 4 54 Air standard Liquid environment e A w Z e 0 2 c r 0 F gt if A hn fh lil y i 0 5 10 15 2 2 Distance Z nm Ida Vuelta 60 80 100 120 Distance Z nm Fig 4 54 Force vs Distance curves in air and in liquids In liquids the adhesion force is greatly reduced As a consequence the values for the parameters of the Jumping Mode are slightly different than those used when working in an air environment For example e Ju
37. ell coupled to the micrometer If not the motor will not move the micrometer 52 To fix the Retaining Springs follow the next instructions Fig 4 19 With one hand steady the head while with the other hold a retaining spring You will notice that the L shaped piece of the retaining spring has a hole marked by the orange dotted arrow You have to place the L shaped piece into the side screw marked with a continuous green arrow using the retaining spring hole Fig 4 20 After placing one of the Retaining Springs do the same with the one on the other side NOTE While you insert the first retaining spring with one hand with the other hand you must hold the head If you are using a MFM head you have to be more careful In this case the head has no magnets so it is not magnetically fixed to the chassis After placing the first retaining spring always hold the head with the other hand do not let go of the head until placing the second retaining spring 9 Once you have secured the head use the two manual screws to approach tip and sample until they are close but without crashing It is advisable to move them with your thumbs as shown in the next images see Fig 4 21 and 4 22 If you turn the screws clockwise the head will approach to the sample and if you turn them in the other direction the head will withdraw Fig 4 21 Fig 4 22 10 Turn on the laser and check again the photodiode position Once it is tuned
38. ers first of all it is usual to take P 2 1 but this is not a hard and fast rule A higher value for the feedback this means P and I higher allows a faster response of the system There will come a time if these parameters are set too high at which the system will begin to oscillate in Dynamic Mode you can easily see this by looking at the Amplitude and Phase images channels CH15 and CH16 respectively In Contact Mode it 1s useful to monitor channels CH1 and CH2 the Normal force and Lateral Force It 1s important to find optimum values for these two parameters They should be as high as possible but without introducing spurious oscillations into the system Jumping Mode The important parameters in this mode are Set Point in the Control Menu Jump off Jump sample and Control cycles in Jumping Parameters Menu and the Feedback parameters P and I in the Feedback Menu e Increase decrease the Set Point value to approach withdraw the tip and sample by piezo movement e As we have said previously the Frequency value in the control Menu is not relevant To control the speed of the system you must adjust the Jump off Jump sample and Control cycles All of them are inversely proportional to the scanning speed so you can try to reduce them as much as possible but you must allow the system to faithfully react to changes in the topography of the sample in order to obtain the best image possible e In terms of Feedback parameters it is d
39. etermined in much the same way as in Dynamic and Contact Mode 12 HOW TO SAVE IMAGES 32 To save images select the images you want to save by enabling the Save checkbox for each of them in the Viewer Options menu see Fig 4 31 In the Acquisition Menu select Saving Options or click El Acquisition iew sc Stan Finish settings select Head Lever Settings saving Options Representation Acquisition Lithography Exit Fig 4 48 A window will appear as shown in Fig 4 48 You can select the folder where you want to save the images their name and a number counter which will appear in the image name and which will increase automatically each time you save an image The extension in the image file name will show the type of image acquired and if it has been acquired using the Fwd or Bck signal For example f top means a Fwd Topography image b ch15 means a Bek Amplitude image f chl16 means a Fwd Phase signal image f chl means a Fwd Normal Force image and b ch2 means a Bck Lateral Force image Saving Options Selected Folder C A WSXMDEV_8_4 Data ie Selected Name MyFile Number to begin ooon Continuous Saving Fig 4 49 Once you have selected a folder specified a name for the images and selected the ones you want to save by pressing El in the Control Menu the Save icon will turn yellow as well as the headings of the images to be saved Note that when the Save button is not
40. ews and the motor approach the tip to the surface until the distance 1s smaller than 1 millimeter Watch the tip reflection on the surface 1t helps to approach tip and sample A magnifing lens and good illumination may help to approach tip and sample Try to keep the STM head level Ah Y Fig 5 5 Manual coarse tip approach Watch the tip reflection on the surface Cover the microscope with the bell jar and if possible with a box to isolate from acoustical noise as much as possible Close the Approach Menu and then click first on Gb and then on YA Check that the Head Parameters match those in figure 5 5 Click again on G0 and set all the parameters of the Control and Feedback Menus as in the next figure 85 NE Mame Smal F Active Type STM Approach Type Joc Motor Sian Positive Negative Eb rim O Piezo Settings gt Freq H 2 9 9 766 A cal nm E Points 128 cal im ja sof rant eb E Z cal amA 14 woti ale Piezo Polarity a E olf nm af Piezo Mame Antonia Load _Load Angle o AS 2 Bias ini 200 Preamp Gain mv tra 100 F in CEDEN mafi Bias Gain i Signal Gair Allow High Voltage bias E Gain 10 ma Bee Blas Offset ro oy an an Lom fo High fO ani a 1 H 5 Up Scan en I Fast STM Head Middle f Smooth Update Cancel Down Secure Fig 5 6 Head and Control
41. f jo Advanced Update Main Linear Feedback On y ilt n m o 4 gt Update K Delay ms 20 Jumping No bafety Z Lift nm 5 4 Round percent 20 4 A LAA ScanZ _ sy Dynamic Yes V Keep Comments when saving image Retrace No Non linear correction Fig 4 32 In the Viewer Options menu for each image as initial settings select the options shown in Fig 4 32 you can display the parameters controlling each view in the Viewer Options menu by just clicking on the corresponding image For example in Fig 4 32 the parameters for View N 2 are the ones shown in Fig 4 31 As another example for view N l we have Channel Topo topography Oscilloscope mode On button _Osci pressed and Fwd Bck signals at the same time On button F B pressed There are two traces one for the left to right scanning direction called Forward Fwd colored in blue and the other one for the opposite sense Backward Bck colored in red To activate a particular view in the Main window View N 0 double click in the view and WSxM will take it to the Main window You can learn more about viewer options and other menus in the WSxM software manual 59 Different views 18 Now is the time to approach tip and sample Select the Approach Menu by pressing 2 You will see the following window Approach A ES Motor Voltage V r Motor Step Time ms 50 gt
42. ge value changes by clicking the arrow To produce smaller changes click the arrow while pressing SHIFT or CRTL for even smaller ones This is important even more when you are very close to the right position between tip and sample in order to achieve the proper Set Point value All the parameters in WSxM can change in this way An alternative way of approaching tip and sample you can use in very special situations consists on increasing the Amplitude to the cantilever driving piezo but this is a CRITICAL process In case you do it make sure you take low increments for the amplitude for example increments of 0 01 V and watching what happens Once you have the tip close to the sample with Fwd Bck signals equal and flat it could happen that the green bar which tells you how much elongated is your piezo scanner is not centered If the green bar is far away from the center and the Z Gain 1s 15 or 10 we do recommend to step the motor in the Approach Menu After scanning for a while you may notice that the green bar has drifted from its centered position You do not have to make Step approaches to re center the green bar Instead you can use the Z offset Zoff in the Control Menu There are two options by software and or by hardware To do it by hardware first of all make sure the knob in Dulcinea 1s in the middle range 5 Then enable the icon beside the Zoff and you will be able to center the green bar by turning the knob
43. h _ po Feedback Ch E 7 17 Selecting the images to display e In the Viewer Options Menu see Fig 4 31 This menu is usually already opened button You will have JE No 2 Channel Topography nm Filter Offset Oscif Fwd Bek F E Horiz Views number 4 je Vertical W Save Fig 4 31 The next figure summarizes Fig 4 32 the above discussion by showing a typical configuration for the screen with the most important menus opened 58 Control menu Feedback menu Scan Options menu E WsxM 4 0 Develop 6 1 Acquisition Started Acquisition Yiew Scanning Advanced Window Help imply 2 EA com elele f 22 Size mmj apy Freq Hz 1 01 alel Points 256 afe xof l Yoff fo fr Sfo f Angle fo lol HY Bias miv 0 lol Set Point v fos8 lol Signal Ganf afl 4 Z nm 1629 95 a Linear Step Y EE EEE Inv Chri _ a f Ilatea 0 023 P View nef2 y Channel Topography nm Fiter Offset Oscif Fwd Bek F AS aM AWannels Yiewer Auto XY Gain 10 gt Mo 3 Gain in ale u Mid Down Secure y Horiz Views number 4 rl o Vertical V Save Z Gain 10 afe A am E Gain out Xx Gain out Y Amplitude W Frequency Hz p Y Scan dle f Smooth E 23409237 l P 20 al gt Feedback Ch Amplit y fo de Phase Deg 109 E Filter out H2 faoeza l input 2 Fra Scan Sensitivity KH2 V oss
44. h the tweezers as shown in Fig 2 26 Then do the same with the other side removing the rubber strip from the top part of the cantilever holder Fig 2 26 Removing the rubber strip 4 Take a new rubber strip and place it in the top part of the cantilever holder The two points in the rubber strip show the position of the holes used to fix it to the top part of the cantilever holder Place one side of the rubber strip holding it with your fingers and the tweezers A possible way to do this is shown in Fig 2 27 Fig 2 27 Placing a new rubber strip 25 5 Place the other side of the rubber strip as shown in Fig 2 28 pes TEA EAT e Fig 2 28 Placing a new rubber strip 6 Finally replace the top part of the cantilever holder to 1ts original position and tighten the screws with the screwdriver pressing the top part down with your fingers as shown in Fig 2 29 to get the top part properly fixed while tightening Fig 2 29 Replacing the top part of the cantilever holder with a new rubber strip 26 7 Finally you have your cantilever holder with a new rubber strip ready for placement of a cantilever chip see Fig 2 30 Fig 2 30 Cantilever holder with a new rubber strip 2l Once you have mounted a cantilever you can place the cantilever holder in the head as shown in the next image Two magnets will hold it at the right position In case of MFM there are no magnets the cantilever holder
45. hassis just plug in the connector and make sure it is well connected Fig 2 13 Dulcinea connection Detail in Fig 2 2 showing the DB37 connector and the cables coming from Dulcinea To Head To Head HV Fig 2 14 Dulcinea connection Dulcinea back view 17 Now you have to insert a cantilever into the cantilever holder If you use silver paint to fix the cantilever place a small drop of 1t on the cantilever holder and then insert the cantilever chip waiting at least 2 3 minutes to allow the silver paint to dry If you use the mechanical fixing method follow the next instructions INSTRUCTIONS FOR USING THE CANTILEVER EXCHANGE BAY CEB To use the cantilever exchange bay CEB to exchange cantilever chips an SPM user will need the parts illustrated in Fig 2 15 below Tweezers CEB fork CEB stop Cantilever holder Magnets CEB base Fig 2 15 Required parts 1 Place the cantilever holder on the CEB base as shown in Fig 2 16 Fig 2 16 Positioning the cantilever holder on the CEB base 18 2 Using the CEB fork align the two prongs with the rubber strip as shown in Figure 2 17 NOTE If you are using a MFM cantilever holder which does not have a magnetic base you must be more careful You must position the cantilever holder with one hand while stretching the rubber strip with the CEB fork Fig 2 17 Positioning the CEB fork under the rubber strip 3 Once you have positioned the CEB fo
46. he head and the cantilever you are using since they have different backside coatings 51 NO INTENSITY BAD BETTER BEST Laser On C Off Photodiode j z Photodiode Optical 3 Optical Optical Tune Photodiode ENET Tune Photodiode cOn Tune Photodiode pean Fig 4 14 Fig 4 15 Fig 4 16 Fig 4 17 Notice in Fig 4 14 that if you do not have signal in the photodiode red and green crosses appear centered but you know there is no signal because there is no blue bar HEAD POSITION AND MANUAL APPROACH 8 Turn Off the laser by clicking Off in the Photodiode window and place the head above the sample the head fixes to the support screws magnetically unless you are using a MFM Make sure not to touch any head micrometer screws in order not to change the previous laser tune and also make sure not to crash the tip If there 1s any doubt about crashing raise even more the support screws before placing the head Once it is placed you can fix the head with the two L shaped parts anchored to the base with springs Retaining Springs see Fig 4 18 Three micrometer screws placed in a triangular pattern make the head support see Fig 4 18 The two screws at the front can be moved by hand while the other is motorized and controlled through WSxM but it can be also moved by hand pushing the motor down with one hand and moving the screw with the other If you move it in this way after the movement make sure the motor is w
47. he signal coming out of the dynamic board plotted as a vector therefore 1ts value 1s the square root of the squares of the X and Y values It 1s written in green because it corresponds to the green curve in the lower window Use the buttons on the bottom of this box to perform a Phase Scan or a Linear Scan independently of the other scans You can use them to fine tune the frequency of resonance or 1f you have lost the resonance frequency for any reason and you do not think it is necessary to go over every step of the tuning When working on Dynamic Mode the phase 1s set in such way that the X component amplitude is negative Increasing the Set Point bringing it closer to zero therefore moves the tip closer to the sample as is the usual case in SPM 91 Appendix B Basic Channels Viewer and Control commands Size determines the size of the portion of the sample that will be scanned Freq determines the frequency in Hz lines per second 1 e 1Hz means one line per second at which the sample will be scanned It is proportional to the speed at which the tip will move across the sample Points determines how many data points will define the image Start with a low number of points if you plan to test a new or different feature That way the test scanning will take less time X and Y off determine the X and Y offsets on the sample You can view the portion that is being scanned using the Position Window see Fig B 1 below Z
48. ical microscope PA a en RUE O A p 35 Installation TST Aa p 36 MCU TNS CL CUO IN no a cletisss p 42 Use OPS Optical MUCIOSCOP Emisores p 42 Chapter 4 First Use of System Hardware amp Software A A err errr eecree rn errr ere ae eee p 46 Laso AHS A A p 47 Head Position and Manual Approach o oooooooooooooononoccncnccnnnnnnnnnnnonnnonononnnoss p 52 Approach m Dynamo Modest p 54 Approach T COn act M OUE epson EEO EA p 63 Approach in Jumping MoOde ooccccnnnnnnnnnnnnnnnnnnnnnnnnnnnnonnnononnnnnnnnnnnnnnnnnnnnnnnnnnnnns p 68 How Acure Mares eera E E p 71 PHONO AVS HA OCS ee E PO E OE p 73 Td O VC ita p 74 Measurements in Liquid Environmentt cccccccseeceeececeeeeeeeeeeeeeeeaaaeeeaes p 75 Chapter 5 Tutorial on HOPG Use of Air STM Head EAN AAA E Na p 82 Appendix A Date Meier p 90 Appendix B Basic Channels Viewer and Control Commands ccccccccnccnnnnnnnnininininos p 92 Appendix C Jumping Mode ccccccnnnnnnnnnnnnnnonnnnnnnnnnnnononnnnnnnnnnnnnnnnnnnnnnnnonnnnonnnnnnnnnannnnnns p 97 Appendix D AY and LOS ies p 98 Atomic force microscope images of a DNA molecule partially covered with gold The right image shows a modification introduced by the AFM tip From LNM Laboratorio de Nuevas Microscopias Departmento F sica de la Materia Condensada UAM Chapter 1 Dulcinea electronics 1 Description Dulcinea is an electronic system specifically designed to control SPM equipment While the mo
49. igurable BNC monitors Using the Scanning Dulcinea outputs menu in WSxM software 4 you can select a specific signal to monitor Please note that A and B BNCs have a low pass filter of SOK Hz while C and D have a low pass filter of 800KHz Dulcinea Back View BNC Connectors RS 232 DB9 Connector P E IN ADC auxiliary channels IDC dept P OUT DAC auxiliary channels HV Connector BNC Connectors IDC 20 Connectors P Power 90 to 240 V ac 50 60 Hz Fuse 2A Fig 1 2 Dulcinea Back View BNC connectors target specific signals to monitor and allows for external inputs o AC Mode BNCs only useful when Dynamic Board is installed VCO Out Driving signal to vibrate cantilever 10V PID Out Phase Lock Loop PLL output only useful when PLL has been activated in WSxM software I Out Driving signal for magnetic cantilever oscillation It is an AC current source with the same frequency as the VCO Out selected in the WSxM tapping menu Ext In Input signal Allows input of an external signal for the dynamic mode reference 10V o General use BNCs Sum Output sum of the four photodiode quadrants Z Mod Input signal Allows input of a modulation voltage to be applied to the Z piezo voltage with gain 1 It has an allowed input range of 10V The maximum input frequency allowed is 10 KHz Bias Mod Input signal Allows input of a modulation voltage to the Bias Voltage between the tip and the sam
50. ill acquire a new look since the color scale has been modified To update the entire image you can the repaint button right hand side of the top banner that contains the names of the views You can change each of these values by typing in the desired value or you can use the arrow buttons located to the right of each number These values are only used for real time imaging and do not affect the data saved in the hard disk The icons on top of the image in the main window are used as follows a Zoom use it to zoom in on an image Click on its icon and select the center of the square region that is going to be zoomed by clicking on it On the Status bar two boxes will show you the matrix and the real points over which the cursor is positioned Click the mouse button again and the zooming process will begin WSxM will start scanning the zoomed portion of the image therefore the Size and the Offsets on the Control Menu will change Measure use this command to measure over the image On oscilloscope view it is used to measure the horizontal and vertical distance between two points on the profile of the sample Click on this icon and select the two points by moving the markers over the profile The vertical and horizontal distances will be displayed on the status bar When using this command on an image view the status bar will display the matrix coordinate equivalent to pixel coordinates and the real coordinate equivalent to
51. io rr Points 258 alo xott mmja ale Yoff gt Sz off mijo gt Angle jo gt HYP Bias mfo alo SetPoint ivi oz fr Signal Ganf a Z Bain fia afl Auto Y Gair po a i Secure Middle Smooth er mj Fig 4 38 21 In the Scan Options see Fig 4 39 select Dynamic No Jumping No and Retrace No Then the system will work in Contact Mode If you have not done a Dynamic tune then the Dynamic Mode option will be disabled as shown in the next figure 63 Scan Z Dynamic Ha You can see the values of the different channels in the Channels Values Menu see Fig 4 29 22 Selecting the images to display e In the Viewer Options Menu see Fig 4 31 select the views as shown in the next figure 10 l Topograp 2 D2 Topograp 3 Normal fi 05 iFf4 Lateral fo Fig 4 40 64 In the Viewer Options Fig 4 31 for each image as initial settings select the options shown in Fig 4 40 How to do it is explained in step 17 23 Now is the time to approach tip and sample Select the Approach Menu by pressing 2 You will see the following window Motor Voltage Motor Step Time ma Force difference to Range w Advanced is position Move Shep withdraw Withdraw Approach Approach Fig 4 41 The parameter to control the Move Approach option is Force difference to range V The value shown in Fig 4 41 0 2 V should be OK but if you want to be very careful wi
52. is fastened by two clamps The three ball system ensures a good stability for the cantilever holder Fig 2 31 Cantilever holder in the head e Finally once you have properly assembled the AFM system computer Dulcinea and the hardware you can check that everything is properly connected by switching on the system running WSxM turning On Off the laser in the Photodiode Menu and moving the motor up and down with the commands Withdraw Approach in the Approach Menu To do this follow these instructions 1 Turn Dulcinea electronics on and run WSxM You will find the following options Re DA LY ER Fig 2 32 2 Select the Data Acquisition option by pressing PA Then the following icons will appear Lica Par JP eon eal AA 110 I MO Ik Fig 2 33 28 3 Check that the parameters of the system you are going to work with are suitable For that click on 4 Select Head 3 Ed Mame Large Iv Active Type AFM Approach Type oc Motor Sign Positive Negative Piezo Settings cal rm 25 Y cal my 235 amp cal rim 35 Piezo Mame Antonio _ Load Piezo Polarity Configurators rz AY range vy 150 af to iso zZ range mf S0 afH to iso Bias Gain 1 Allow High Voltage bias Bias Offset mw Low i o High lo Offset Speed nmz 4720 Angle jo OR Cancel Fig 2 34 Select the piezo you are using changing the calibration va
53. lecting the channel in the Viewer Options menu of the WSxM software o Out DAC Auxiliary channels Three output channels 12 13 14 are available for the user through these BNC connectors They can be used for DC output voltages and multiple feedbacks In addition the SCRIP Lithography in WSxM allows user program outputs o Frequency Mod Only useful when the Dynamic Board is installed this monitor BNC will allow you to visualize the voltage that comes from the DSP board controls the frequency modulation in the 3dModes Frequency Z or in the digital PLL working mode HV Connector This connector has all the high voltage usually 150V outputs coming from the Dulcinea electronics RS 232 DB9 connector P Serial connection with the computer Power 90 to 240 V ac 50 60Hz Fuse 2A Power supply input Compatible with power supplies from 90V to 240V including American 110V and European 220V and AC frequencies of 50 to 60 Hz Universal power supply it comes with a 2Amperes fuse for short circuit prevention and there is also a replacement 2A fuse included in the same place Safety instructions Never touch the High Voltage part of the electronics while the unit is powered on It has dangerous voltages that can cause severe damage including death When powering off the electronics please take care of waiting a minimum of 30 seconds before powering it on again Keep the electronics away from water Keep the electronics away fr
54. lues 1f necessary Your piezos have been calibrated at Nanotec and the calibration values are written on a label attached to the piezo cables Please check that the sign of Zcal is correct For Dulcinea users it must be negative The motor you have is a DC motor Sign Negative Make sure that the checkbox Active in the top of the window is checked before exit If this box is not activated your changes will not be updated Now click OK Then press 60 and Dulcinea electronics will initiate enabling the rest of the menus SP iec gov Sart Be A AE EE AA MA Fig 2 35 29 4 Turn on the laser by clicking on Mi The Photodiode Menu will appear Photodiode Tune Photodiode Optical power Fig 2 36 e Select On to turn it on The laser should turn on To turn it off select Off 5 Select the Approach Menu by pressing You will see the window shown in Fig 2 37 Approach E Approach Motor Voltage MW 7 d Motor Woltage M Motor Step Time ma 50 d Motor Step Time ma Force difference to Range M 0 2 d Force difference to Range w Advanced Z Plezo Advanced Plezo position position Step Move Step Withdraw Withdraw Stop withdraw Approach Approach Approach Approach Move Fig 2 37 Fig 2 38 30 The Approach Menu controls the motor There are two options Move and Step e Move the screw rotates in a continuous movement e Step the screw rotates in a disc
55. mp off can be as small as 10 nm e Jump sample when jump off is very small use a number of steps higher than the jump off the higher the jump sample the more stable the measurement will be but 1t will take longer as well you need to find a compromise e Control cycles since the jump sample is not as large as in air the number of cycles can also be small Minimum value allowed is 4 cycles the higher this number the more stable the measurement will be but it will take a longer time as well you need to find a compromise 78 Dynamic mode The cantilever holder for measurements in liquid environment has a piezoelectric see Fig 4 55 in order to oscillate the cantilever for Dynamic Mode Fig 4 55 Piezoelectric marked by red arrow in the liquid cell In this case the piezoelectric is far from the cantilever to avoid contact with the liquid environment and the whole cantilever holder 1s vibrated This implies some important differences with respect to Dynamic Mode in air The spectrum will show not only the peak corresponding to the cantilever resonance frequency but other peaks corresponding to mechanical resonances of the whole system cantilever holder plus cantilever see Fig 4 56 When working in liquids the resonance freq of the cantilever decreases to approximately 1 3 of its value in water see Fig 4 57 The Q of the cantilever decreases in liquids and the peak is wider 79 0 45 0 4 0 35 0
56. mum and Maximum Frequencies in a rational way For example for a cantilever with f 71 kHz and k lt 1 N m the default values in the 54 dynamic window should be OK we will refer to this cantilever in following examples as cantilever_1 However for one with f 250 kHz and k 40 N m cantilever 2 in following examples you have to change at least the Maximum Frequency to for example 450000 Hz Another important parameter is the Amplitude of the voltage applied to the cantilever driver piezo You have to select a value in order to get a reasonable resonance peak see Fig 4 25b It 1s recommended to start with a low value 0 25 V and increase decrease it 1f necessary depending on how much you want the cantilever to oscillate If the amplitude of the cantilever driving piezo is too large your resonance peak would resemble that shown in Fig 4 25a The other important parameter is the Delay The system needs some time to perform a good dynamic tune It is advisable to place a Delay value higher than 150 To learn more on Dynamic Mode see Appendix A 13 Once you have set the parameters discussed above press Tune and WSxM will search automatically for the resonance frequency of the cantilever The next figure shows two images as an example The one in the left corresponds to a saturated resonance peak and the one in the right to a non saturated resonance peak R gt mn gt e E Z T T s 2 E Fa o 5
57. ncrease the Set Point value If Fwd Bck signals become the same by suddenly flattening gt OK you are in the right conditions to measure Center the green bar with step approaches withdrawals and close the Approach Menu If the piezo gets fully extended go to case A above If the piezo is fully retracted check the vertical green bar shown in the Control Menu and in the Approach Menu this represents the Z piezo displacement If the piezo is fully retracted there will be no green bar Also there will be no evident variations in the Fwd Bck traces check the Normal Force value CH1 in the Channels Values Menu see Fig 4 29 You should find that the CH1 value is higher than the Set Point which is why the piezo has retracted You must enter a Set Point a bit higher than the CH1 value for example if CH1 0 6 V you could enter 0 65 0 70 V The piezo will extend and you the situation will be covered by the above discussion either the piezo will or will not be fully extended Follow the suitable instructions given above depending on the system state 66 Fig 4 41 Fig 4 42 Fig 4 43 Fig 4 44 Fig 4 41 after the motor Move approach stops the system is in range but tip and sample are not close enough Fig 4 42 after changing the Set Point and making some Step approaches Fwd Bck traces start to be flat and equal Changing just a little more the Set Point will lead to a sudden flattening of Fwd Bck traces Fig
58. nfo al Auto Y Gainfio 100 a F Middle Smooth Secure Fig 4 27 e Asa general rule set the initial Frequency to 1 Hz and the Number of Points to 256 Fields colored in grey must be changed using the arrows on their right Some fields can be changed and the new value will be directly updated and in other fields when changing the value the background turns yellow When this happens they must be updated by first pressing the Update button or Enter key on the keyboard To learn more about the other parameters in Control Menu see Appendix B 56 15 In the Scan Options Menu see Fig 4 28 This menu 1s usually already opened button Select Dynamic among the possible measurement modes In case none of them 1s selected the system will work in Contact Mode The final configuration should be Dynamic Yes Jumping No and Retrace No Scan p ynamic e Jumping Ho Sp afety 2 Lift rim 5 4 Retrace Mo ound percent 5 4 Wait a few seconds to give time for the system to change into Dynamic Mode and press Update in the Control Menu Then the values of the different channels will be updated in the Channels Values Menu This menu 1s usually already opened If not you can see it by pressing see Fig 4 29 e The Set Point value in the Control Menu Fig 4 27 will be used by the feedback system to control the tip sample distance In Dynamic Mode the feedback channel is the Amplitude of the
59. ng to work with are suitable For that click on 4 Select Head 3 Mame Large IV Active Type AFM Approach Type oc Motor Sign Positive Negative Piezo Settings cal rm 25 Y cal rim 235 amp cal rim 35 Piezo Mame Antonio Load Piezo Polarity Configuration rz AY range vy 150 af to iso En Z range qu a FO al to f0 al Bias Gain 1 Allow High Voltage bias Bias Offset mw Low W o High lo Offset Speed nm 4720 Angle jo Ok Cancel Fig 4 3 46 Select the piezo you are using changing the calibration values 1f necessary Your piezos have been calibrated at Nanotec and the calibration values are written on a label attached to the piezo cables Please check that the sign of Zcal is correct For Dulcinea users it must be negative The motor you have 1s a DC motor Sign Negative Make sure that the checkbox Active in the top of the window is checked before exit If this box 1s not activated your changes will not be updated Now click OK Then press 60 and Dulcinea electronics will initiate enabling the rest of the menus LASER ALIGNMENT AND PHOTODIODE TUNE 6 Turn on the laser by clicking on MI The Photodiode Menu will appear Tune Photodiode Optical power Fig 4 5 e Select On to turn it on e Adjust the laser beam to be focused on the cantilever by using the micrometer screws closest to the laser s
60. not move with the motor e The AFM head can be safely handled as shown in the next figure Fig 2 41 Handling the AFM head Do not touch the optical parts in the AFM head optical cubes laser photodiode Take special care not to touch the laser or 1ts cable since this might cause misalignment It is also advisable not to touch the micrometer screws after you have positioned the laser on the cantilever and performed the photodiode tune e If you use silver paint to fix the cantilever to the cantilever holder do not use liquids to clean the silver paint from the holder Particles of silver paint could get between the different parts of the holder producing undesired electrical contacts 34 Chapter 3 Optical microscope 1 Description The optical microscope that Nanotec provides with the AFM system can be divided into four different parts It is shown in the next image Camera Optical Microscope Stand Optics Light source optical fiber Fig 3 1 Optical Microscope 35 2 Installation instructions First of all it is necessary to assemble the optical microscope stand A diagram showing the different parts is given below We will follow that diagram to explain the steps of the assembly See figure 3 2 3 b Grey Block L Manual screw Allen yA screws Fig 3 2 Optical microscope stand diagram 36 e Fix the upright column of the stand the metallic cylinder we refer to as leg p
61. om electromagnetic radiation sources Never open the electronics unit without the previous agreement of the manufacturers Never change the fuses for a different type 3 Installation instructions In your Dulcinea based system you will need the following items Dulcinea electronics Computer system CPU screen keyboard and mouse with preinstalled Digital Signal Processor DSP RS 232 Serial cable Please notice that your computer has a DSP installed if two flat cables IDC50 are coming out from the rear panel Before starting the installation please make sure that you have all the needed components and that both the electronics and the computer have the power supply cable unplugged The RS 232 cable communicates between the computer and the Dulcinea electronics It is needed for WSxM to recognize that Dulcinea electronics is installed Connect this cable from COM1 or COM2 serial port in the computer to the Dulcinea rear panel RS 232 connector The cables labelled From DSP analog multi color and From DSP digital gray going out from the computer carry real time signals required for the proper working of the electronics You should connect From DSP analog cable to the From DSP analog connector located on the rear of Dulcinea and From DSP digital cable to the From DSP digital connector Finally you should connect the To Head and To Head HV connectors to your SPM he
62. ormal Force CH1 you can see it in the Feedback Menu Fig 4 30 The system keeps it constant comparing the Set Point value with the Normal Force value from CH1 you can see it in the Channels Values Menu Fig 4 29 and the tip sample distance is changed to keep the Normal Force constant To set an initial value for the Set Point before approaching check the Normal Force value channel 1 CH1 in the Channels Values Menu see Fig 4 29 As you have tuned the photodiode in the Photodiode Menu making the red and the green crosses to coincide the normal force and the lateral force should be 0 Place the initial Set Point around 0 2 0 4 V 26 Open the Jumping Parameters Menu by pressing 2 P Topo From Last Control Point gt 2 Motion Jump off rim 500 gt Jump sample Jeo al Control cycles ET a Mon contact samplin Distance nm lo Delay lo Stifinezz Points fro Offset correction f None C Fast Slow Bias always On To Fig 4 45 Now we will explain the parameters To learn more about Jumping Mode see Appendix C 68 Topo From in this box the user can select how to process the data points that WSxM will use to construct the topography of the sample The DSP continuously acquires data while the feedback loop is closed which means that the tip is in contact with the sample During this time many Z data points are acquired by the DSP The exact number depends on
63. out 8 KHz Gain in Amplification factor of the normal force signal coming from the head to the dynamic board You should increase the gain 1f the output signal from CH15 or CH16 is too low for example if the output signal is smaller than 0 3 V Gain out Amplification factor of the signal coming out of the dynamic board and going to the DSP You can use it for the same reason you use the Gain in amplification It 1s better to use the Gain in amplification because the dynamic board works with the amplified signal Be careful not to saturate the output Default limits Click on this button to set the WSxM default values for the Max and Min frequencies Info box In this box WSxM will display information about the normal force signal coming out of the head into the dynamic board Resonance Frequency of the cantilever oscillation When running the cursor over the graphs it will turn into a crosshair Use it to click on any point you want to obtain numeric information WSxM will provide you with the following information about the point Frequency value of the point selected by the cursor X component of the signal coming out of the dynamic board plotted as a vector It is written in red because it corresponds to the red curve in the upper window Y component of the signal coming out of the dynamic board plotted as a vector It is written in blue because it corresponds to the blue curve in the upper window Amplitude of t
64. ple distance at which a specific measurement will be done Set this number by typing it in or use the arrow buttons Delay Set here the number of cycles this new measurement will require Type in the number or use the arrow buttons Stiffness The stiffness is defined as the slope of the jumping Force Distance data after jump to contact A least squares fit to a straight line is performed to accurately estimate the slope Points set here the number of points used to a fit line to the contact region of the force vs distance data Type in the number or use the arrow buttons Bias always on select it if you want the Bias always on Otherwise the bias will be on only when measurements are being done as non contact sampling You can learn more about the jump mode by consulting the following references Jumping Mode in Scanning Force Microscopy by P J de Pablo J Colchero J G mez Herrero and A M Baro App Phys Lett 73 3300 1998 Jumping Mode and Tapping Mode by F Moreno Herrero P J de Pablo J Colchero J Gomez Herrero and A Baro Surface Science 453 152 158 2000 Atomic Force Microscopy Contact Tapping and Jumping modes for Imaging Biological Samples in Liquids by F Moreno Herrero J Colchero J G mez Herrero and A M Baro Phys Rev E 69 031915 2004 97 Appendix D XY and Z Gains In any digital acquisition system in order to obtain data with the best resolution you should take care that
65. ple with gain 1 It has an allowed range of 150V The maximum input frequency allowed is 10 KHz IDC50 Connectors P IDC50 male connectors for low voltage communication with the SPM head and the Digital Signal Processor DSP which is inserted in a PC slot inside the computer o To Head Connector with the low voltage 10 V signals that go to the SPM head In Nanotec Electronica systems you will have to connect here the cable labelled Po Head o From DSP Analog Connector with the low voltage 10V analog signals coming from the DSP You will have to connect here the multi colour cable labelled From DSP Analog o From DSP Digital Connector with TTL control signals coming from the DSP You will have to connect here the gray cable labelled From DSP Digital IDC20 Connector P Digital In Out DC20 male connector with user available in out digital signals It gives trigger signals configurable by software in the WSxM View Digital Signals menu and it receives digital inputs from the Nanotec Electronica counter electronics BNC Connectors o In ADC Auxiliary channels Four input channels 8 7 6 5 are available for the user to introduce any low voltage 10V signals These signals will automatically be measured by WSxM software and they will be acquired synchronous with the scan generation allowing the user to map these signals with respect to the piezo scan You can view and save these signals by se
66. pressed these headings are red and the ones which will not be saved are blue When the scanning reaches the end of the scanning square top or bottom the images get saved and the Save button switches off If you select Continuous Saving the save button will change into Tial and after pressing it the system will not switch it off until after sequentially saving your files 73 When the Continuous Saving option 1s selected the selected images will be saved every time the scanner reaches the top and the bottom of the scanning square TURNING OFF DULCINEA 33 Stopping the acquisition and turning off the system BEFORE TURNING OFF Dulcinea electronics ALWAYS EXIT WSxM To exit WSxM stop scanning This 1s easily accomplished by entering a value of 0 to the Size in the Control Menu After the scanning has stopped move away the sample from the tip using the Approach menu by clicking Withdraw in the Move option allow the tip to withdraw a reasonable distance and turn off the motor The Withdraw button will change into a Stop button and you will have to press it to stop withdrawing Using the two micrometer screws see Fig 4 22 withdraw totally the tip from the sample Leave the Feedback parameters on P 20 and I 10 Put the X Y and Z offsets to 0 Just in case leave the gains on 10 if not while closing WSxM this will automatically occur Once you have completed these steps you can finish the acquisition by pressing the STOP
67. r holder Then place the chip cantilever sliding 1t to 1ts final position e Mount the cantilever to the cantilever holder designed for liquid environments You can fix it either with grease see Fig 4 51 or with a rubber strip Fig 4 52 depending on your application Fig 4 52 Move the rubber strip to expose the chip mounting platform Place the chip cantilever and then hold the chip with the rubber strip e Align the laser onto the cantilever with the help of the parking screen e Due to the sapphire window two different laser spots will appear on the Hand held screen The spot corresponding to the sapphire window will always be there while the spot related to the reflection from the cantilever will only appear when the laser is properly aligned onto the cantilever usually showing a characteristic diffraction pattern e Put the SPM microscope head onto the three micrometer adjustment screws 76 Before putting any liquid into the pool manually approach or use the motor the cantilever to the sample until you see a distance of about 1 mm between the chip of the cantilever and its reflection on the sample After you introduce the liquid the cantilever sample distance will not be easily seen Remove the SPM head from 1ts normal position and fill the pool with liquid Now return the SPM head to its position over the sample A liquid capillary will form between the cantilever holder and the liquid surface see Fig 4 53 Pl
68. rete way with short displacements in each step Press Move Withdraw and the motor should start moving raising the screw To stop it the Move Withdraw button will change into a Stop button see Fig 2 38 If you press Stop the motor will stop While withdrawing if the motor goes down then it is approaching it means that probably the motor connection see Fig 2 10 is connected the wrong way so check it If the laser and or the motor do not work stop the acquisition pressing In Dulcinea electronics a shutdown message will be received then turn it off Check all the system connections and make sure all of them are firmly fastened especially the DB37 connector on the base of the hardware see Fig 2 13 Repeat the above process and try again The laser and the motor should now work 31 e To finish with the AFM Hardware we will discuss how to use the Retaining Springs see Fig 2 2 Once you have placed a sample on the sample holder you will position the AFM head with the cantilever holder and a cantilever on the micrometer approach screws see Fig 2 2 At this time you have to use the Retaining Springs to fix the head to the chassis These springs act as a final antivibration measure With one hand take the head while with the other take a retaining spring as shown in the next image Fig 2 39 32 You will notice that the handling piece of the retaining spring the L shaped one has a hole see
69. rk under the rubber strip stretch the rubber strip by pushing the CEB as shown in Figure 2 18 Fig 2 18 Stretching the rubber strip 19 The entire CEB fork will now fit onto the CEB base The CEB stop see Fig 2 15 and Fig 2 19 will clamp the CEB fork into position with the rubber strip stretched as shown in Fig 2 18 leaving an open space in which to place the cantilever chip CEB fork CEB stop CEB base Fig 2 19 Diagram showing the CEB fork position held in place on the CEB base by the CEB stop after stretching the rubber strip 4 Using the tweezers slide a cantilever chip into the appropriate position as shown in Figure 2 20 Fig 2 20 Inserting the cantilever chip 20 5 Once you have inserted the cantilever chip carefully re position the rubber strip with the CEB fork being careful not to touch the cantilever chip as this may result in damage to the cantilevers Fig 2 21 Final positioning of the cantilever chip underneath the rubber strip 6 When you have moved the rubber strip over the cantilever chip as shown in Figure 2 21 lower the rubber strip and remove the CEB fork see Figure 2 22 If the cantilever chip needs slight adjustment in the cantilever holder you can adjust the cantilever chip position using the tweezers Fig 2 22 Removing the CEB fork ZN 7 Finally you have the cantilever holder with the cantilever chip in place and ready for use see Figure 2 23 Fig 2
70. s voltage to 100 mV In the Freq Hz field in the Control Menu set 14 In the Round Percent field in the Scan Options set a high value 70 to avoid the effects of the high scan speed of the piezo You should see some kind of periodic structure on the screen If the scan size 1s increased the number of features should increase accordingly Try to improve the image by playing with the Bias voltage and Set Point values As a general rule the image will improve by itself as the time goes by Try to increase the value of the P and I The periodic structure will appear also in the Topo image P 2 and I 1 could be reasonable values but you can try higher ones though always avoid oscillations If you want to save the images select the path and name using the Saving Options El Remember there are not clear conditions to obtain good images You have to take into account the next facts e Small Bias between 25 and 300 mV is usually a good option e The Set Point can be between 0 5 nA and 8 nA 88 e As smaller the P I values the response of the system will be slower That usually gives good current images but poor quality topographic images e Experiment also with the frequency and the number of points to improve the Image e You can change the X Y offsets to scan another place on the surface e Change the Angle to scan using another side of the tip 34 If after 30 minutes playing around you are not able to obtain a periodic str
71. select None the system will identify the point of zero force as the value you set when you made the photodiode tune If you select Fast Slow you will activate the offset correction at different times during the scan The Fast offset correction will adjust the point of zero force at the end of each scan line while the Slow offset will perform the adjustment after each jumping point 69 27 In the Scan Options see Fig 4 46 select Dynamic No Jumping Yes and Retrace No If you have not done a Dynamic tune then the Dynamic Mode option will be disabled as shown in Fig 4 46 15 Safety Z Lift mf Sound percent A Hon linear You can see the values of the different channels in the Channels Values Menu see Fig 4 29 28 Selecting the images to display e In the Viewer Options Menu see Fig 4 31 select the views as shown in Fig 4 47 hal Selected Channel ams hal Channels Viewer Fig 4 47 70 In the Viewer Options Fig 4 31 for each image as initial settings select the options shown in Fig 4 47 How to do this is explained in step 17 As you can see in Fig 4 47 in Jumping Mode the system is performing an F Z curve at each point in the image From this data it is possible to make Adhesion and Stiffness maps This can be done by simply selecting Adhesion and Stiffness as channels to display 29 Now it is time to approach tip and sample The process is the same as in Contact Mode
72. since it is negative you have to change it to values closer to 0 If Fwd Bck traces get the same with a sudden flattening gt OK you are in the right conditions to measure Center the green bar with step approaches withdraws and close the Approach Menu If the piezo gets fully extended go to case A Fig 4 34 Fig 4 35 Fig 4 36 Fig 4 37 Fig 4 34 after the motor Move approach stops the system is in range but tip and sample are not close enough Fig 4 35 after changing the Set Point and making some Step approaches Fwd Bck traces start to be flat and equal Changing just a little more the Set Point will lead to a sudden flattening of Fwd Bck traces Fig 4 36 Fwd Bck traces after doing what has been said in Fig 4 35 Fig 4 37 the system is in the proper feedback range obtained after waiting one or two seconds from Fig 4 36 IMPORTANT Once you have done the Motor Move Approach then some Step Approaches and also some Set Point increments if the system is not in the proper feedback range you can set a scan size for example 2000 3000 nm and continue with the Approach Instead of seeing a sudden flattening of Fwd Bck traces when the system gets the proper range you will see topography traces which can be more visual to know when the tip is close enough to the sample NOTE You can change the Set Point value directly typing its value but you can do it also using the arrows in the dialog box You will get lar
73. st immediate application 1s to the control Nanotec Electronica SPM products Dulcinea is designed in an open and modular way in order to facilitate interfacing with any other AFM SNOM STM system Dulcinea Front View Configurable BNC Graphic display 240x128 connectors for monitoring 10 turn adjustable potentiometer Software activated LED active Indicator Push switch Fig 1 1 Dulcinea Front View Graphic display Notifies the user about events like the start end of the communication with the computer and gain changes It is also available for future implementations Z Manual 10 turn adjustable potentiometer Software activated This potentiometer can be used for manually adjusting the Z Offset applied to the piezo For its use it needs first to be enabled by software using WSxM selection available in the Control Menu During normal operation the Z Offset is set by software and this knob is only used for special applications It is important to only enable disable it by first moving to the intermediate 50 position The maximum offset you can apply is 50V Z Manual LED active Indicator This LED will be on when the manual offset is active Z Secure push switch At any moment you can press this button to generate an offset voltage of 150V to the Z piezo voltage This allows fast withdrawal of the tip from the sample without using the software BNC connectors for signal monitoring A B C D Software conf
74. th your tip you can reduce 1t until 0 1 V As the zero force level will drift during approach due to long range cantilever sample interaction the Force difference to range tells the system to look for a sudden change of the Normal Force equal to the selected in this field 24 Once the parameters are set press Approach in the Move option If Z Gain in the Control Menu is not 15 the maximum one WSxM will suggest that it be changed to this value to allow the Z piezo to move through its entire range if necessary The screw will move until the tip is in range Then the motor will stop and the piezo will extend retract you can notice this by looking at the vertical green bar shown in the Control menu and in the Approach Menu which represents the Z piezo displacement If the piezo is fully extended the green bar will be at its maximum If the piezo is fully retracted then the green bar will disappear You will also notice that there will be no topography Fwd Bck traces e How to know when the tip is close enough to the sample When the system is working properly the Fwd Bck traces should be similar At the beggining before scanning Size 0 display the Topo view in oscilloscope mode with a viewing scale of 2 nm and Filter Offset This means that the tip is close enough to the sample and the system is in the proper feedback range Since the sample is not scanning and the tip is just 65 above the sample there is no topogr
75. the data you want to measure fits as well as possible into the range of your system In this way you will avoid digitalization problems The Dulcinea SPM controller is based on 16 bit DACs Digital to Analog Converters and ADCs Analog to Digital Converters This means that for any continuous value that you enter the maximum number of different values will be 2 65536 Those 65536 different values are correlated to voltage values between 10V and 10V With the maximum gain 15 you can produce up to 150V If the topography you want to measure is rough i e one micron your measurements will use about 10000 different values so you will get good data but if you want to measure very small features like Inm heights the data will have only 10 different values so you will not have very good data and you will find that the data is limited by your digital system resolution So the ideal way of measuring small features 1s to have a small voltage range like 5 10 times the range of your data it is better not to adjust 1t too much because you could get out of range but you would like this small voltage range to be centered around the maximum limits set by your piezo elongation This is why it is so important to center the green bar and reduce the XY and Z Gains 98 Low coverage images showing Pb adsorbed on a Si 111 7x7 superstructure The UHV STM images have been simultaneously taken using the retrace facility in WSxM Image size
76. the value entered into the Control cycles dialog box Choose Average of Control Points if you want to use the average of all the data points acquired on during contact to make the topographic image or choose Last Control Point if you want to use only the latest data point measured The Z motion box allows you to input three important parameters They are Jump off maximum distance between the tip and the sample on every jump If you are using a Short piezo scanner insert an initial value of 500 nm If you are using a long one use an initial value 1500 nm Jump sample the number of steps taken during each jump This number is inversely proportional to the scanning speed AS initial value use 60 Control cycles the time the tip spends with the feedback closed in contact with the sample after every jump It is also inversely proportional to the scanning speed AS initial value use 20 These three parameters control the speed of the piezo scanner movement As we have already emphasized the Frequency in the Control Menu is not relevant It is possible during a jump image that the Z piezo may drift To compensate for this possibility an Offset correction dialog box is provided The Offset correction allows you to keep the Normal Force applied by the tip to the sample constant that is you can make the difference between the Set Point and the point of zero force when the tip is far from the sample always the same If you
77. traces are not similar just after motor approach you must make further adjustments There is a number of possibilities to consider A If the piezo is fully extended maximum green bar in the Control Menu and in the Approach Menu You will also notice it because there will be no topography Fwd Bck traces variation continue to approach the tip toward the sample For this e Use the Step option in the Approach Menu giving the necessary steps to center the green bar it is advisable to get 1t centered while measuring because then the Z piezo will move over the maximum range in both directions up and down e Increase the Set Point value since it is negative you have to change it to values closer to 0 until getting Fwd Bck traces the same reaching this state with a sudden flattening of them If the piezo gets fully extended again before the traces flattening repeat the above process When Fwd Bck traces become equal center the green bar by making step approaches When the green bar is centered close the Approach Menu B If the piezo is not fully extended there are two possibilities e Fwd Bck traces are flat and constant having reached this state by the appearance of a sudden onset of flattening The system is in the proper feedback range Center the green bar by making step approaches withdrawals and close the Approach Menu after the green bar is centered e Fwd Bck traces are not flat and constant Increase the Set Point value
78. u will observe an indicator bar that appears as a short vertical line one pixel in width as in Fig 4 29 This means that your gain is large you have a lot of extra range To improve image quality you can step by step decrease the Z Gain After each step you will perhaps find out that you need to readjust the Z Offset At one moment you will see that the red vertical line for the Z value in the Channels Values Menu is not a line but a bar As you lower the gain the bar gets wider That means that you are using a Z range comparable to the range of your data so your image will be improved Take care not to decrease the gain too much 71 because this might move the tip out of range you might obtain saturated data or much worse you might crash your tip For more information about the XY and Z Gains see Appendix D 31 In order to obtain good images you will need to adjust some parameters Dynamic and Contact Mode The important parameters in these modes are Scanning Frequency Freq Hz and Set Point in the Control Menu and the Feedback parameters P and I Proportional Integral in the Feedback Menu button e Increase decrease the Set Point value to approach withdraw tip and sample by piezo movements e You need to set a Frequency value which allows the system to react to the changes in the topography of the sample Scanning frequency value is usually in the range from 0 5 to 2 5 Hz e In terms of Feedback paramet
79. ucture withdraw the head cut the tip and try again You can also take a new fresh HOPG surface using a piece of tape as explained in step 2 35 If you have cut the tip 3 times without good results something else is wrong Fig 5 9 Example of Air STM Topography and Tunnelling Current images 89 Appendix A Dynamic Menu When pressing Tune in the Dynamic Menu WSxM will go through different kinds of scans to find the resonance frequency First it will make a scan over the frequency range selected by the user on a logarithmic scale that way it will roughly find the resonance frequency Secondly it makes a linear scan over a shorter frequency range set by the results of the first scan to fine tune the resonance frequency Then it performs a phase scan to determine the phase of the incoming signal The ultimate result is a determination of the amplitude of the oscillation and its phase The Nanotec system assigns the phase signal as the input to Channel 16 and the amplitude as the input to Channel 15 When performing the phase scan the resonance frequency might change Therefore to finish the search WSxM goes through a last linear scan to get the actual resonance frequency The values shown in the parameter boxes will usually be different from those set at the beginning They will be the last parameters determined from the last scan You can make WSxM repeat any of these processes separately by using the buttons on the left
80. um intensity Then move the laser beam along the cantilever length use screw 1 until the spot is at the edge of the cantilever you will notice that because the diffraction pattern gets distorted with rings appearing in addition to the maximum Fig 4 8 The next three diagrams shows an approximation to the diffraction patterns corresponding with the most usual cantilever geometries Diffraction patterns for three of the most common cantilever geometries are shown Parking Screen Diffraction Pattern Hand held Screen Diffraction Patterns EEKE LAKK 000 OMe oe Please observe that the drawing is not to scale Fig 4 10 49 Parking Screen Diffraction e 00 Gre 00 CIC v yer Hand held Screen E Diffraction Patterns __o e eoghosoco o Please observe that the id DON e OK drawing 1s not to scale s po Fig 4 11 AR DI pap cam ene Parking Screen Diffraction Y An ag Patterns wae S N l 7 N N 7 N a e di a w i Sl So Se Hand held Screen Diffraction Patterns Please observe that the drawing is wy O GG ox not to scale e Fig 4 12 50 Screw 3 for coarse Screw 2 for laser vertical adjustment of alignment on the cantilever the photodiode Screw 5 for fine horizontal adjustment of the photodiode Screw 1 for laser alignment on the cantilever Screw 6 for fine vertical adjustment of the photodiode Screw 3 for coarse vertic
81. um name Album type Import From Fay 3 Floppy A EB Discolocal C cy Windows 2000 D a Creative E cy Backup F Fig 3 8 Add Album Then you can select the folder you want to save your files in Finally if you click Source see Fig 3 5 a dialog will appear x Camera Controls Image Controls M Full Auto Mode Compensation White Balance f Auto Freeze indoor ncandescent Auto fe Shutter Speed Gain E Fluorescent Outdoor User Defaults Save Restore Factor Defaults Restore Flickerless f 50H E Hz Close Fig 3 9 Properties 40 Fig 3 10 Example of a complete system configuration IMPORTANT e Fora proper use of the optical microscope the stand should be placed behind the AFM chassis placing the optical microscope above the AFM head moving the optical arm from the right That is why it is advisable to plug the optical fiber coming out from the right in order not to have anything above the AFM head when the optical microscope is removed This arrangement insures that it 1s possible to place the glass cover while using the AFM system e The light source induces mechanical vibration please do not place it on the same table as the AFM chassis and head 41 3 Safety instructions e When operating with the optical microscope you will need to tighten and loosen the manual screws in order to position the mi
82. urrent n Simple Fine Approach Piezo poskan Move Step Withdraw Withdraw Approach Approach Fig 5 8 Approach menu 87 20 21 2 29 24 23 26 2i 28 29 30 31 32 33 Set the parameters as shown in the figure and click on Fine Approach The green bar will start to move up and down This motion reflects the motion of the Z piezo element At the central position of the green bar the motor is switched on during the time indicated in Motor Time After several steps the head will be in range Be patient depending on the tip sample distance that you have left after step 11 this process can last for several minutes When the In range message shows up click on Update Control Menu the green bar will go all the way up If Fwd Bck current signals are oscillating reduce P and I as necessary i e 0 6 and 0 3 respectively or even lower to avoid the oscillations Click on Step Approach until the green bar will be slightly above the center Close the Approach Menu and incrementally decrease the Z gain to 0 29 If you are using the manual positioning of the z piezo adjust the z manual knob as necessary to keep the green bar near center Change the Zoffset in the Control Menu or using the knob in Dulcinea if it is selected to set back the green bar to the central position Start to scan by setting 8 in the Size nm field in the Control Menu Reduce the Bia
83. vide a description of the different components Head Parking Piezo scanner Motor base Security brakes to fix the optical table while transporting it Micrometer screws to move the optical table Optical table Sorbothane balls Fig 2 1 Chassis To Head cable To Head H cable Security brakes to fix the optical table while moving it DB37 connector from Dulcinea LEMO female connector for the head Mierometer motor approach screw 3 A e Sample holder Micrometer manual approach screws Fig 2 2 Chassis top view 10 Optical cubes Photodiode LEMO male i A connector Ph Micrometer screws for laser alignment on the cantilever Screws for coarse Micrometer screws adjustment of the for fine adjustment photodiode of the photodiode Fig 2 3 SPM Head Photodiode Cantilever holder Cantilever Motor base Fig 2 4 SPM Head cutaway view Detail of the SFM head showing the laser path through the optical system in red 11 Fig 2 5 Piezo scanners long and short Fig 2 6 Cantilever holder A glass cover bell jar is provided with the system to reduce acoustic and environmental noise as well as to perform atmosphere control Fig 2 7 Glass cover 12 The Cantilever Exchange Bay CEB is a metallic base and fork designed for easy placement and removal of cantilevers Fig 2 8 Cantilever exchange bay CEB Other elements which are not sho
84. wn in the images Metallic cover for the chassis you will see it in Fig 2 12 e Standard cantilevers for starting up e Silver paint and scalpel to fix remove the cantilever on from the cantilever holder in case you prefer this method instead of the mechanical one e Rubber strips for cantilever fixing e Computer with DSP inside and computer monitor CD with WSxM software and DSP drivers already installed 13 2 Installation instructions When you receive your AFM system 1t should appear as in figure 2 1 except the piezo scanner it will not be installed Take the sorbothane balls out of their package and place them under the chassis as shown in Fig 2 1 If you have an optical table after you have placed the chassis in your laboratory loosen the optical table brakes to easily move the optical table with the micrometer screws Since the piezo scanner is one of the most fragile parts of the system it is packed separately from the rest of the chassis and you will have to place it in position To do this refer to the next diagram Grooved brass screws i Piezo scanner LEMO CONNECTOR FGG 18 LEM CONNECTOR PHG 1B Fig 2 9 Piezo scanner assembly e The grooved brass screws are already placed in their final position in the motor base so you will find them there You have to fix the piezo scanner to the motor base with them but you do not have to tighten them very strongly stop when you realize they are

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