Optimizing The Tappingmode Afm Signal After Engagement - Veeco 004-210-000 Instruction Manual

2.5.2 Optimizing the TappingMode AFM Signal after Engagement

The figures on the bottom of
voltages.
There are some basic rules to remember:
1. The setpoint voltage is always lower than the RMS voltage.
2. The difference between the RMS voltage when the tip is off the surface, and the setpoint
voltage dictates the amount of damping or "tapping force." The larger the difference, the
greater the tapping force.
3. The RMS voltage controls the amount of energy that is in the cantilever (figs. A and D). This
is important to note because some samples are stickier than others. The tip may stick and,
therefore, be held to the sample surface if the RMS amplitude is too small.
The initial setup for TappingMode AFM is to:
4. Tune the cantilever at its resonance.
a. Select View > Sweep > Cantilever Tune (or click the Cantilever Tune icon).
For Auto Tune Controls , make sure the Start Frequency is at 100kHz and the End
Frequency is at 500kHz . Target Amplitude should be 2-3V .
b. Click Auto Tune . A " Tuning ..." sign should appear and then disappear once Auto Tune
is done. When done, quit the Cantilever Tune menu.
c. Set the Peak Offset to 3-10 percent . The Peak Offset is the percentage of the
cantilever's free-air resonant frequency to be automatically offset. Peak offset is used to
compensate for changes in resonance before engagement due to the tip's interaction
with the surface after engagement. Range and Settings : 0-50 percent. Positive values
offset the Drive frequency rightward on the graph.
5. Engage the microscope.
Rev. B
Figure 2.5a show the relationship between the RMS and the setpoint
MultiMode SPM Instruction Manual
SPM Fundamentals for the MultiMode
Review of TappingMode AFM
45