Instruction manual

Force Imaging
Force Modulation
210 MultiMode SPM Instruction Manual Rev. B
14. Adjust the Integral Gain, Proportional Gain, Setpoint, and Scan Speed to obtain a good
topography (Height) image. For force modulation operation, set the Integral Gain and
Proportional Gain to values of 1-10 and set the Setpoint as low as possible using the cursor
keys (or by typing in new Setpoint values) until the cantilever pulls off the surface and the Z-
center voltage jumps to -220V.
15. Record the Setpoint value where the cantilever pulls off the surface (the “pull-off value”).
16. Increase the Setpoint until the cantilever touches the surface, and an image appears. Then
decrease the setpoint to a value just above the value where the pull-off occurred.
Note: If you adjust the Setpoint very close to the pull-off value, imaging perform
with the smallest and least damaging force. However, in this condition imaging
may be more unstable, as the cantilever may pull off the surface unexpectedly.
The setpoint value affects the force modulation contrast. Examine the contrast
of the force modulation image.
17. Optimize Drive amplitude for Force Modulation imaging. The amount of contrast and the
quality of both Height and Amplitude images depends on the Drive amplitude. In general,
increasing the Drive amplitude provides greater contrast in the force modulation image.
Note: It is possible to set the Drive amplitude too high. If this occurs, the Drive
amplitude no longer increases the contrast in the amplitude image. Instead, the
overall contrast in the force modulation image remains roughly constant, but
you will observe more artifacts in the image. For example, if the drive
amplitude is too high, the force modulation image becomes contaminated by
“edge effects” or “friction effects.” Operate at the lowest drive amplitude that
gives sufficient contrast to examine the sample. Low drive amplitudes also help
extend the life of the cantilever tip and reduce sample damage.
Procedure for Optimizing Drive Amplitude
1. Start with a small Drive amplitude value of 50mV.
2. Increase the Drive amplitude with the right arrow keys or type in new values. The contrast
of the Amplitude (force modulation) image increases.
3. Continue increasing the Drive amplitude until sufficient contrast appears in the Amplitude
image. If the Drive amplitude increases to the point where contrast is no longer improving,
reduce the Drive amplitude slightly.
Note: Force modulation contrast also depends on the Setpoint. In general, if using a
larger Setpoint (larger tracking force) use a smaller Drive Amplitude to obtain
good force modulation images without artifacts. If it is difficult to obtain a clear
force modulation image that is free of artifacts, try reducing or increasing the
Setpoint and then optimizing the Drive Amplitude.
4. Readjust gains (if necessary).