Forms

LineScan

Press the Lin Button to take a line scan of the image. First select two points of the image by pressing the left mouse button. The linescan is displayed in the upper linegraph of the linescanform-window. To perform measurements on the linescan press the Measure button.

Use the left mouse button to select a new point. With the right mouse button you can switch between points. Pressing the Shift button allows to move a whole line. Pressing the right mouse button together with the Shift button will switch to the prependicular averaging mode.

Important: If the linescan form is opened through the menue selection first, all linescan data will be displayed always in the this particular window. Otherwise pressing the LIN button will always open a new window.

Autosize Selects automatic scaling of the linegraph

Autolinebacksub Selects automatic subtraction of linear background

Line Display Trackbar Move to show a line scan of a particular image line. A FFT of the selected line is shown in the lower line graph.(The number of points/line has to be a power of 2)

Popup menu of upper linegraph xydesign: Select to adjust the appearance of the line graph CopyClipboardData: The line scan data are copied to the ClipBoard CopyClipboardXYGraph: The line scan graph is copied to the ClipBoard Printxygraph: The line scan graph is send to the printer Measure: Do measurements of the plot data. Redrawline: The line in the image is redrawn

Popup menu of lower linegraph has the same items as the upper popup menu and one additional entry: Show Frequency: Gives the FFT in frequency [Hz] instead of inverse distance [1/Å] (updated when the Line Display Trackbar is moved)

Channels Select the channels which are displayed

Rampcontroller

Click on the Ramp button. This opens the 'Rampcontroller'-window with control elements necessary to perform the coarse approach. The 6 buttons with arrows in the top of the form correspond to moving the tip in respect to the sample surface. Moving in x/y direction can also be done using the x/y cursor keys on the keyboard. The page up and page down keys are used correspondingly for rotation up and down. Selecting the burst mode in x/y or rotation will result in a series of steps corresponding to the number of burst steps displayed in the ramp parameter list. When the Crash Protection is switched on, the program checks before each step, whether it can detect a tunneling current. If this is the case it will cancel the step. Usually the crash protection should be switched on, but in cases where the tip is already crashed, the protection has to be switched off. The program issues some warnings when the ramp windows opens to inform the user to do necessary changes for a successful ramping. These are: First retract the tip, reset the x- and y-offset in the STM-program, select the appropriate gain (1-10, depending on the temperature) in the x- and y- channel of the HV-amplifier and set the external offset voltages to zero. The usual coarse approach is done by controlling the approach with an optical microscope. When the tip is close enough, the automatic tip approach can be switched on, by pressing the Approach button. It will start a combination of single coarse approach rotation steps combined with tip approach testing until the tip can reach the sample. Approach stops when a tunneling current is detected. The value of this threshold current is set by the current slider. Important: When the approach stops, the tip is automatically retracted, by setting the current to zero. Before leaving the coarse approach by pressing the Quit button, you have to select the mode for scanning. When the Main/Coarse button displays 'Coarse' mode, then the outer 3 piezos are used for scanning, otherwise the center piezo is used. In the normal operation of the microscope the 'Coarse' mode should be selected. Select the required set point current to see if the approach was successful. Now the tip should be retracted manually by using the external HV-amplifier z-offset voltage to go out of tunneling. Select the required gains and re-approach the tip again.

See also: Approach Tips

The Coarse Approach operation is controlled by the following parameters:

Puls Height[V] Input the peak to peak height (in V) of the sawtooth pulse used for moving the inertial slider. Two different values are used for the lateral XY motion and the rotational motion.

Puls-Duration[sec] Input the duration of a single sawtooth pulse in seconds.

Burst-Count Determines the number of sawtooth pulses applied when operating the coarse control in burst mode.

Approach Period[sec] Determines the time for a single approach cycle including approach and retraction of the tip to find the sample surface.

Approach Burst Count This is the number of coarse pulses applied between two approach cycles.

Approach Retry Count This is the number of retry operations done before the approach is stopped.

Grid

The form 'Grid-Image- Transformation' contains several functions for different kinds of image transformations. A suitable combination of the procedures below will allow transformations useful for drift correction, superstructure analysis, extraction of registry information. To open the form press on the grid button in the STMAFM form. With the 6 slider controls a grid can be overlayed on the image. The lateral position, the angles of the grid and the distance between the grid lines can be adjusted. An alternative way to input the grid is pressing the Mouse button and to mark 3 points (the first one is the center, the other two determine the direction of the two lines). Pressing the Rotation button will rotate the image in such a way that one set of the grid lines (X-Axis) is parallel to the horizontal direction. Pressing the Zoom button will zoom the image by the value set in the edit control positioned next to the right of the button. The image is zoomed around the center point of the grid. By pressing on the X..,Y.. button the actual center position of the grid is stored and displayed on the button. Selecting a new center position with the mouse, as described above, and pressing the Move grid to Center button will move the new defined center to the stored center position. The Transform button will transform the image according to the 2 Parameters in the edit controls below. The first is the new angle between the lines in the image and the second is the new ratio the grid line distances. Selecting the HexGrid check box will draw a grid suitable for hexagonal unit cells. If draw inverted is selected the grid is drawn by a inversion process. Otherwise you can select with <Grid Color> the line color of the grid.

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TimeSpectrum

It is very often useful to take a time record of the A/D input channels, without scanning or changing the biasvoltage. This is for example a convenient way to characterize the noise performance of the STM. To take a time record just press the Start Button on the Time-Spectrum window or press the TS button on the main window. Five channels are recorded simultaneously. The A/D channels 0 and 3 (ADC0 is called current I) and the topography signal output from the feedback loop, called Z. The displayed channel is selected by the corresponding channel button. Three parameters control the data acquisition:

Spec_Points The number of data points taken for a single spectrum. This must be a power of 2, to allow FFT of the data. (Maximum is 4096)

Spec_Freq[Hz] The sampling frequency. (Limited by the DSP_Clock value)

Spec_Avrg_Count The number of spectra averaged. Averaging is done only for the spectrum, i.e. the FFT data.

Channels First select the check boxes to determine the channels which are acquired during data acquisition Part of these channels can be further selected to be displayed.

The results are displayed in two line graphs. The upper one shows the time behaviour. (The vertical scale is always in V) The lower one shows the frequency spectrum. (The vertical scale on the left shows the peak to peak value of a pure sine component, the right scale the rms amplitude for non correlated signals)

The frequency resolution depends on the number of points and the sampling frequency. Important: The current signal and the ADC1 signal are filtered by a first order digital filter, which is controlled by the same CurrentRC Parameter. The contents of the memo field is saved together with the file.

In the lower right the AVRG Value and the Standard Deviation of the timespectra data are shown.

Save The data is saved in ASCII Format

FFT logscale: Displays the Spectrum in LogScale

Waterfall: Displays the time dependence of the Spectra in a Waterfall like mode at the bottom of the window

3d-view

This part of the program allows the display of 3d views of selected parts of the images. To start, open the window by clicking the 3d View button. Then click on <New Data> in the main menue and select a rectangular region on the image displayed in the STMAFM program. A new form will be opened, where the rendered image is displayed. The sliders in the 3d-view form allow to change the orientation, size, offset and lighting of the 3d object. The 3d image can be displayed in different ways, depending on which check boxes are checked. So the lights can be switched on or off, the 3d image can be shown using lines, hidden lines, or in the normal surface view. Checking the save box will start saving of each images displayed. With this feature a series of BMP images for movies can be created. Checking the Box box will draw a 3d box with x,y,z axes in the 3dimage.In the light sources field the angle of the light source can be changed. Apart from a directed diffuse light source ambient lighting can be added.

Under the menue item Color the color of the background and of the lines can be changed. Morover the image can be copied to the clipboard (in BMP format), to a new window or the data can be exported in PoVRay format. (New List means that a new imagedisplaylist is created for the underlying OPENGL rendering program. This usually done automatically)

Selected views can be saved and are saved with the program.

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Lateral Manipulation

To perform a lateral manipulation with the tip one has first to press the Button LM and then to select the starting and the final position of the manipulation path by selecting these points in the image with the left mouse button. A thin line is drawn on the screen between these points. After the manipulation is completed a separate window opens up where the tip height and current during the manipulation is displayed. By pressing the save button this data set can be saved in a *.LAT File.

Different kinds of manipulation procedures can be performed. They are selected by choosing a certain manipulation mode number in the manipulation parameter field. These different modes are described in the following. The speed of the tip is controlled by the parameters latmandelay and latmanddx, which are used throughout the whole process and not only when the tip is manipulating.

Mode 1: This is the simplest constant current mode manipulation. Starting from the top of the image the tip moves in a straight line to the starting point of the manipulation using the standard feedback parameters used for imaging. Then the feedback parameters are switched to the ones selected in the lateral manipulation parameter set . These are current, voltage and gain of the preamplifier. Then the tip moves using these manipulation parameters to the final position. There the parameters are set back to their original imaging values and the tip moves back to top of the image.

Mode 2: Similar to mode 1, but the tip moves first to the final position, then starts the manipulation to the starting position and goes back to final position. It switches back to imaging parameters and moves to the top of the image.

Mode3: Similar to mode 1: The tip first moves to the starting point. Then it moves to final position and back to the starting position using the normal imaging parameters, but the tip height and current are recorded during these two scans. Then the parameters are switched to the manipulation parameters and the tip moves to the final position. Then the parameters are changed back to the imaging parameters and the tip moves back to the starting position while again recording the tip height and current. Finally the tip moves to the top of the image.

Mode 4: This is a constant height manipulation mode. The tip moves first to the starting position. Then it moves from the starting to the final position and back taking data in normal imaging mode. Then the feedback is switched off and the tip moves from the starting to the final position in constant height mode. The height used is given by the height of the tip when the feedbackloop is switched off plus the additional offset given by latmanccdz. This means that the height depends on the imaging parameters. Then the tip moves back from the final position to the starting position in imaging mode, but taking data again. Finally the tip moves to the top of the image. With the extension factor the manipulation path can be extended at the final position by the factor given by latmanextlextension. The starting point is not affected by the extension factor.

Mode 5: Similar to mode 4. In this mode the extension affects also the starting position. The extension positions are first calculated. The tip moves in imaging mode to extended starting position. Then moves to the final extended position and backward and takes data in imaging mode. Then the tip moves to the starting position, while taking data in imaging mode. Then the tip moves from the starting position to the final position in constant height manipulation mode. Then it moves back to the starting position in imaging mode and takes data. Finally it moves back to the top of the image.

Mode 6: Similar to mode 5. The only difference is that the tip moves from the starting to the final position and backward in constant height mode and not only in the forward direction, as done in mode 5.

Mode 0: This mode is different from the other modes. In mode 0 the tip follows always the mouse position immediately. The height of the tip is displayed on rate meter appearing on the left. By pressing the upper case L key the imaging parameters are switched to the manipulation parameters and back again. (By pressing the upper case S a small 64 pixel * 64 pixel scan is performed.) Clicking with the mouse button will stop the continuous following of the tip. After additional clicking the tip moves to the new mouse position in a straight line and tracks the mouse position again.

These parameters control the lateral manipulation processes.

Mode Select one of several different manipulation modes. There are constant current and constant height modes. For example P0 is the origin of the image. Then the tip moves to P1, the first point selected with the mouse. The tunneling parameters are changed to manipulation parameters and the tip moves from P1 to P2. There the normal tunneling parameters, used for imaging, are selected again and the tip moves to the origin P0.

Voltage[V] The tunneling voltage applied during the manipulation phase.

Current[nA] The current used during manipulation

Gain preamplifier The gain used during manipulation

Manip. Speed[Å/sec] The speed of the tip for lateral movements. Used for all movements. Step Size determines the number points measured during a lat. manip. scan.

Extension Extension value for manipulation modes 4-6

Const. Height Z-Offset In constant height mode the tip sample distance can be varied by this parameters. Positive values [Å} correspond to a closer approach to the surface.

Channels Select the channels acquired during data acquisition

LatChannelForm Press to open a new Form to display the manipulation data.

Lateral Speed [Å/sec] Speed at which the tip is moving from the origin to first starting point

LM in old place Repeat the LM using the previous coordinates

Load Ext Lat Par Load the lateral manipulation cooordinates from an external file.

The measured data is displayed in separate windows. X and Y scaling can be adjusted by the user. Two independent axis can be displayed. (Press 2.Axis) LP Low Pass Filter TP Makes the Windows transparent to put it on top of another window.

Right click to open the Popupmenu. XYDesign, XY Series Edit allows to change the appearance of the Data Copyclipboard.. copies the Plot or the Data into the clipboard PrintXYGraph prints the XY Plot Measure allows measuring the distance between points in the plot AutoUpdate: The Plot is updated every second during Data Acquisition. Lowpass filters the data (very simple just nearest neighbor average)

Vertical Manipulation / I/V Spectroscopy

Vertical manipulation (spectroscopy) is started by pressing on the VM button and selecting a point in the image by clicking with the left mouse button. The tip uses the lateral speed value to move to the vertical manipulation position. When the manipulation is finished the measured data appears in a separate window and can be saved with the Save button. Different channels can be selected to be recorded. Usually an external Lockin will be connected to ADC1. The internal Lockin supplies the signals dI/dV, d2I/dV2, di_q,d2_q. The form of the voltage and the z-height ramp is controlled by 8 points in time. In the case of the voltage one can define 8 time points and their corresponding voltage value. For example (0,1000), (256,0), (512,2000),(1024,-1000) define a ramp starting with 1000mV at time 0. Then it will be linear interpolated to time 256 with 0 Volt. Then it goes up again to 2000mV at time 512 and finally reaches -1000mV at time 1024. The time values correspond to the number of points taken. In this case these are 1024 points. A maximum of 100000 points is possible. The z-height values already include the gain of the z-amplifier. This means, that changing the HV gain will not change the z-height ramp, because this will be automatically corrected. Vertspecback = 1 will apply the ramp in forward and backward direction. Vertspecback=n will apply the ramp in forward and backward direction n-times (n>=1). The shape of the ramps is shown in the lower graph in the vertical manipulation window.

Vertical spectroscopy can be done during scanning. Press the VM Button and select a point in the unscanned image area.

These parameters control the vertical manipulation and spectroscopy

Gain preamplifier Gain of the preamplifier during data acquisition

Speclenght[sec] Select the recording total time of the spectrum.

Spectrum backward 0: The Spectrum defined in the V,Z table is taken only once. 1: The spectrum defined in the V,Z table is taken once in forward and once in backward direction >1: Defines how often a forward and backward spectrum is taken

Lateral Speed[Å/sec] Speed at which the tip moves to the place where the spectrum will be taken.

Z- Offset Defines an additonal offset which is added to the z values in the table

Z-Drift Defines an increment which is added to the values in the table to compensate drift effects

Repeat Count Defines how many separate spectra are taken and stored.

Spectra/Line Defines the number of spectra equally spaced along a line between a start and endpoint,selected by mouse input. The first spectrum is taken at the startpoint of the line the last one at the endpoint of the line.

V,Z table 4 points can be defined to create a voltage and z table used for vertical manipulation and spectroscopy. The data values are plotted in the graph below. The first Time Value should be set to 1 (not 0, still allowed for compatibility), otherwise the first value might not be displayed. (Voltage(green), Z-Position(blue))

Spec_X_Grid Spec_Y_Grid Determine the spacing of the spectroscopy grid. First spectrum position is (spec_x_grid,spec_y_grid) in pixel coordinates.

SGrid_Channel Number of channels recorded during the grid spectroscopy mode

SpecGrid_Delay Delay in DSP cycle units added before/after a vertical spectrum is started/finished.

SpecAvrgCount Number of Spectra acquired and averaged directly on the DSP board. For Count>1 be aware that the current preamplifier gain for vertical spectroscopy will be set the same to the normal preamplifer gain. Between the spectra the feedback loop will be switched on to readjust the sample tip distance.

SpecAvrgFBDelay On Time of the Feedback loop in DSP cycle units between spectra in Averaging mode.

Save File Save the present Vert. Spektrum

Single_Spectrum Take one single spectrum. Select the position with a left mouse button click on the image. Same like pressing <VM> button

Spectra along Line Take a series of spectra equally spaced a long a line defined by two mouse clicks.

Spec in old Place Take a spectrum at the X,Y position of the previous scan.

Multiple Spectra Select several spectra taken one after the other. Left Mouse button select another spectrum, right mosue button stop selection and start data acquisition.

MultSpec from File Use an external file (Ascii) to define a series of spectra. Only 256*256 pixel images allowed. No zoom. First line contains number of spectra. Each following line contains the x y image coordinates(integer) of each spectrum.

Spectra on Grid Spectra taken at each grid position. (Analysis of the Grid data is done in another program)

SaveSpecgrid Save the Grid File. Two files are saved. One *.specgrid.dat File with all the parameters and the *.specgrid File with the grid data

VFB_Mode Select the VoltageFeedbackMode I(V,z): Normal Operation feedback loop is OFF z(V): Constant current operation

VFB_Current[nA] Current setpoint used in z(V) Mode. FB_Channel has to be current.

Load Vert_Params Load only the parameter of a spectrum and not the data

External VZ Data If not checked the VZ Data for a spectrum are taken from the VZ-Table parameter. If checked the VZData is taken from a different source table, which can be loaded from an external file. This allows the user defined design of arbitrary VZ arrays of up to 100000 points. File format see below.

Filenames: First Letter is the machinename, in case you have more than one LTSTM or you want to assign different users. Followed by DATE.TIME.VERT. VERT is the standard fileextension. In case you take repeated spectra in a point or take spectra along a line an additional "L#Number.R#Number." indicator is added before the VERT file extension. L indicates line position and R indicates the numbering in repeat mode.

The measured data is displayed in separate windows. X and Y scaling can be adjusted by the user. Two independent axis can be displayed. (Press 2.Axis) LP Low Pass Filter TP Makes the Windows transparent to put it on top of another window.

Right click to open the Popupmenu. XYDesign, XY Series Edit allows to change the appearance of the Data Copyclipboard.. copies the Plot or the Data into the clipboard PrintXYGraph prints the XY Plot Measure allows measuring the distance between points in the plot AutoUpdate: The Plot is updated every second during Data Acquisition. Lowpass filters the data (very simple just nearest neighbor average)

Slider

Brightness and Contrast Use the slider window to control the brightness and contrast of the image. The slider marked B adjusts the brightness of the image. The slider marked Z controls the contrast. Above both sliders the corresponding height range in (+/-)Å is displayed.So total height difference between black and white for example is two times the displayed value. On the right for multichannel images the channel, which is displayed can be selected.

Biasvoltage The polarity of the biasvoltage can be changed by pressing with the mouse on 'V' label, or by pressing the +/ - keys.

Press the right mouse button on the 'V' label to open a Popupmenu for the biasvoltage. Three options exist: SetBiasMinvolt: If selected sets the current biasvoltage as the minimum biasvoltage. SetBiasMaxvolt: If selected sets the current biasvoltage as the maximum biasvoltage. This feature can be used to avoid tunneling outside a specific bias voltange range. i.e for example to limit the maximum biasvoltage to protect the tip, when using the silder.

ResetBiasMinMax: If selected deletes the Min/Max values again.

Current Press the right mouse button on the 'A' label to open a Popupmenu for the current.

Log: logarithmic scaling of the current slider Lin: linear scaling of the current slider

Channels Select the displayed channel. For Channel Nr.= 0 all channels are displayed.

Zoom Allowed zoom factors are x1, x2, x3, x4.

Tip up/down Press this button to fully retract or to approach the tip.

The height of the slider window can be adjusted. This changes the height of the sliders simultaneously.

FFT Evaluation

This part of the software allows use to analyse FFT transforms of the images. (Always crosscheck the results)

Load Files

Loading Files is done using the Open *.Dat menu item.

You can define your own favorite directories in the Windows Places Bar region. (Use for example the TweakUI utility.)

Options:

Full Parameter Load: Check to load all parameters, not only those relevant for the loaded file type.

Disable Warning: If checked no warning will be given when files are loaded in data acquisition.

Open allows to select in running program or alternatively in a newly opened analysis program.

AFM

In the following we discuss the operation of the internal PLL system. The internal PLL can operate up to 32kHz ( based on 16 samples per period at 512kHz max sample rate). This usualy covers operation of standard quartz tuning fork sensors as the qPlus sensor. (For higher frequencies optionally the Zurich Instruments PLL can be used externally.) The input signal from the Preamplifier is connected to the ADC3 input of ADDA Board 2, while DAC5 of the same ADDA Board supplies the excitation signal.

PLL Centerfreq: determines the center frequency of the PLL. (Change either by typing the number directly or increase/decrease by using the up/down/ page up/page down and both in combination with Shift key) PLL-Ampl[nm]: Input the Set value of the Amplitude in nm when the Amplitude controller is on PLL-Exc[V]: Input the Excitation value in Volt PLL-Phase: Phase Shift of Exciation Signal. Has to be optimized const stable PLL operation PLL F Range[+/-Hz]: PLL frequency tracking range. max. allowed deviation from center frequency

PLL On: If selected operation of the PLL is switched on Ampl Control: If selected Amplitude Control is switched on Active Damping: If selected the Amplitude control can electronically damp the cantilever vibration Ref Signal f: If selected DAC2 of the PLL board outputs a reference of the PLL frequency Ref Signal 2f: If selected DAC2 of the PLL board outputs a reference of the 2nd harmonic of the PLL frequency

P[Hz/Deg]: Proportional value of the PLL frequency controller Int[Hz/deg/s]: Integrator value of the PLL frequency controller LP Filter[Hz]: Value of the 4th order loop filter P Ampl[V/nm]: Proportional part of the Ampl controller LP Amp filter[Hz]: Loop filter of the Amp controller df Post Filter[Hz]: Filters the PLL freq data finally before it is output to the STM feedback controller

Sensor Cal[V/nm]: Calibrate the Preamp output in nm units SRS Gain: Optionally include the SRS Preamp gain

PLL FreqScan, PLL Phase Scan: Start a frequency or Phase Scan Filter PLL_Scan: Filter the Scan Data. (simple 1.order lowpass). can be repeated to allow a beeter calculation of the Q factor etc. Show Phase: Displays the phase. Has to be selected to calculate the Q Factor.

Results: Automatic determination of CenterFreq and Q Factor

ScancenterFreq, FreqSpan, ScanTime, ScanPoints: determines the properties of the Frequency Scan or PLL Phase Scan

20 steps to successful AFM operation

For a first setup of a functioning PLL useful for scanning in CC, CH or CF mode please refer to the following graphical guide.

In order to start scanning please perform the following steps: a) For constant current mode (CC, dynamic STM) 14. Approach the tip and observe the frequency shift changing from Δf=0 Hz to a finite negative value. 15. Select the channels dF, Amplitude and Damping in the Parameter window in order to measure these signals. 16. Set the current setpoint to a finite value, i.e. e.g., 10 or 100 pA. 17. Start scanning in CC mode as you would do in STM mode.

b) For constant force mode (CF, nc-AFM) 14. Change the feedback mode to LinAbs and the feedback channel to dF. 15. Change the integrator value to e.g. -0.0003 or something in the same order of magnitude. 16. Select the channels dF, Amplitude and Damping in the Parameter window. 17. Set the constant frequency setpoint to a value close to but a little bit smaller than the finite Δf value from above. 18. Start scanning in CF mode as you would do in STM mode. 19. Adjust the scanning speed and the integrator together with the amplitude and phase control of the tuning fork. 20. Observe the current signal and increase the setpoint in order to go closer to the surface.