Maintenance, Troubleshooting and Warranty
Maintenance
340
Dimension 3100 Manual
Rev. D
18.1.2 Calibration
A description of the complete scanner calibration is located in a separate chapter. In general the
scanner’s calibration should be checked every three months. The main change in calibration will be
the loss of piezo sensitivity in the first year of use. This is an expected behavior. Loss of 10-15% of
the initial scan size is common.
Inspections and Procedures
Noise Test Procedure
Although a noise test is performed prior to shipment and during a new installation, this test is useful
to periodically test the instrument’s performance in your lab. Increases in the noise level of the
instrument are typically due to some sort of environmental change such as the introduction of new
equipment in proximity of the D3100 stage. The D3100 system itself is historically not prone to
degrade over time, although changes to the environment are a common source of noise.
Because the Dimension 3100 is sensitive to vibration, it is often a convenient tool for checking the
performance of the vibration isolation system. The following test can be performed under ambient
conditions or while an external noise source is applied to the floor.
1. Install a new cantilever and engage in TappingMode on a Si wafer (500nm to 1µm scan
size). You can also image the substrate of a silicon probe. The probe can be mounted to a
small sample AFM puck with double-sided tape and held to the stage magnetically. The only
limit to this sample is that the vacuum seal between the chuck and the sample won’t be
tested.
2. Set the
Z limit
to
55V
(~1µm). Set the
Samples/line
to
512
.
3. Set the gains as low as possible, while still maintaining a good image with visible surface
roughness. Do not lower the
Integral
and
Proportional gain
below
0.2
; the
LookAhead
gain
should be
0
.
4. Change the
Scan size
to
1nm
and capture an image. The Scan rate is not important for this
Scan size. You can set the
Scan
rate
to 10Hz to save time. If you have low frequency noise,
you may want to set the
Scan
rate to 2Hz so that you can see at least a few periods (longer
time base).
5. Perform a first order
Flatten Auto
. Then, run the roughness measurement. The
RMS value
should be typically
0.5Å
.
An easy way to analyze noise is to use the Section Analysis function. If you draw a line that is
perfectly horizontal, the one dimensional Fourier plot will show you what frequencies are
contributing to your noise. Remember that when the Scan size is this small, you no longer have an
image but rather a temporal graph of the Z displacement.
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