Realtime Operation
Rev. F
Scanning Probe Microscope Training Notebook
37
Figure 16.1a
Scope Trace Demonstrating the Effect of the Setpoint Being Adjusted Too Close to the Free Air
Amplitude During TappingMode AFM
Notice that the tip tracks the surface up the sidewall properly but not down the sidewall with respect
to the scan direction. This occurs on opposite sides of features for the Trace and Retrace scan
directions.
This problem can be remedied by decreasing the Setpoint in TappingMode, or increasing the
Setpoint in Contact Mode.
16.2 Integral
Gain
The Integral Gain controls the amount of the integrated error signal used in the feedback
calculation. The higher this parameter is set, the better the tip will track the sample topography.
However, if the integral gain is set too high, noise due to feedback oscillation will be introduced
into the scan, as shown below.
Figure 16.2a
Scope Trace Demonstrating the High Frequency Noise that Occurs when the Integral Gain is Set
Too High
Setting the integral gain too low may result in the tip not tracking the surface properly, as shown
below.