© ICSPI Corp. 2007-2021
nGauge AFM User Manual 2.0
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5.5.3.
Vertical Scan Range and Fine Z
The Fine Z graph represents the tip height, and it is shown in units of V. When the tip engages
with the sample, the Fine Z should stay around the middle of the range (approximately 1.5 V).
The Fine Z changes during the scan, as the tip tracks the sample topography.
Important:
the Fine Z should never reach either extreme (0 V or 3.3 V) of its range. It is
recommended to monitor the Fine Z while scanning. More details on monitoring and controlling
the Fine Z range are available in the Scan section: 5.7.2 Fine Z and Vertical Scan Range.
5.5.4.
Fine Z Drift
After approaching, you may notice that the Fine Z drifts upwards or downwards. Usually this is
due to sample relaxation, such as polymer relaxation. The MEMS scanners are electrothermal,
meaning that they use thermal energy to move. For this reason, it may take some time before
the tip and sample reach a thermal equilibrium, depending on the sample.
Try clicking on
Disengage
then on
Approach
. If the drift continues, you can coarsely position
the tip height with Z Coarse so that the Fine Z is in the middle of its range or increase the Z Fine
PGA. Refer to 7.3.5 Fine Z Drift and Fine Z Not Centered for more information.
5.5.5.
Advanced Controls
Refer to Section 8.2 Approach Advanced Controls for details on advanced controls on the
approach page.
