Fluid Operation
TappingMode in Fluids
Rev. B
MultiMode SPM Instruction Manual
137
Note:
The slope of the Force Cal curve during probe interaction with the sample
surface is de
fi
ned as the
sensitivity
of the
fl
uid TappingMode measurement. In
general, higher sensitivity results in better image quality. If the sensitivity is
poor, check the mounting of the sample and
fl
uid cell.
8.3.3 Optimizing Image Quality
Adjust the setpoint by monitoring image quality, as follows:
1. Select an appropriate Scan size. Wait until the current scan line is over a tall feature, then
disable the slow scan axis. Select
View
>
Scope Mode
and observe the agreement between
the trace and retrace lines.
2. Increase the setpoint in small increments until the probe pulls off the surface and the
Z
Center
position voltage goes to retracted (i.e.,
-220V
).
3. Reduce the setpoint in small increments until an image appears.
4. Continue reducing the setpoint until the image is optimized.
•
The best images are obtained at setpoints just below where an image appears.
•
The NanoScope Controller attempts to keep the cantilever oscillation amplitude
constant during the scan.
5. Optimize the
Integral gain
and
Proportional gain
so the
Height
trace shows the sharpest
contrast and there are minimal variations in the
Amplitude
trace (the error signal).
6. Optimize the
Scan rate
to obtain the sharpest image.