© ICSPI Corp. 2007-2021
nGauge AFM User Manual 2.0
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Example of Fine Z reaching 3.3 V: the tip has crashed into the sample. The amplitude is below
the setpoint:
If the Fine Z is moving towards the end of the range, go back to the Scan page and click
Pause
then
Reset
. Go back to the Approach page and ensure that the Fine Z is in the middle of its
range.
There are two main settings that affect the scan range: 1) Leveling and 2) Z Fine PGA.
The following two sections will explain how to use these settings to ensure that the Fine Z does
not reach one of the extremes.
5.7.2.1.
Leveling
Ideally, the tip is perpendicular to the sample. There are a few reasons why the tip may not be
perpendicular to the sample:
1)
nGauge AFM chips are installed at a 15º angle relative to the sample to ensure that the
tip comes into contact with the sample;
2)
The tip and cantilever assembly bends away from the chip at a certain angle (see image
of nGauge AFM chip in Section 3.2 MEMS AFM or AFM-on-a-Chip);
3)
The sample itself is also most likely not perfectly flat.
For these reasons, there may be “tilt” in the Y direction (slow scan axis) during scanning. In
severe cases, the tilt may cause the tip to lose contact with the sample as the scan progresses
or crash into the sample.
To correct for this tilt, a voltage can be applied to the Z actuator that increases or decreases
throughout the scan.
To change the direction of this leveling, the
Leveling Direction
can be set to Forward or
Reverse. The recommended default is
Forward
.
To change the magnitude of the leveling, change the
Leveling
setting. The recommended
default value is 5.
The tilt may be device specific. Different types of AFM chips may also require different Leveling
Directions and Leveling settings.
