Calibration, Maintenance, Troubleshooting and Warranty
Contact AFM Troubleshooting
316
MultiMode SPM Instruction Manual
Rev. B
(both of which are on the same side of the chip) will have dif
fi
culties with the laser optics due to
laser beam spillage over the side of the cantilever. This effect is more pronounced for samples
which are highly re
fl
ective.
Using a microscope that has an interferometric objective lens, it is possible to observe
fi
ve or more
contour lines following the length of the legs of the cantilever on a warped cantilever probe.
Cantilever probes which are not warped will have contour lines parallel to the substrate edge.
Nikon® sells interferometric objective lenses for their Optophot and similar microscopes (such as
the MPlan 40(x) DI 0.5 210/0). This is a recommended lens for observing contour lines on the
cantilever for diagnostic purposes. It is bene
fi
cial to use a bandpass color
fi
lter with this lens. Please
consult Nikon for further information.
15.11.8
Image vertical dimensions are not correct
•
When invoking the
Highpass
fi
lter
, height information will not be accurate. The
Highpass
fi
lter removes the DC component of scan information. This will invalidate the
height information in the image.
•
The
Z
Sensitivity
parameter must be calculated (as described in
) or height
data will be inaccurate.
•
When acquiring de
fl
ection data for height measurements, gains must be set low to
reduce movement of the Z piezo.
15.11.9
Z Center Position
goes out of range
The
Z Center Position
voltage is a measure of the average voltage to the Z electrode. The image
will disappear when the Z center position reaches either the fully extended or the fully retracted
ends of the Z center indicator. Possible causes include:
•
Having the
Z limit
too low.
•
Tilted sample. The sample should be as level as possible, particularly for larger scans,
because tilt in the sample can cause the Z scan to run out of range.
•
Mechanical drift will cause the sample-to-tip distance to change slowly bringing them
apart completely, or too close together. If this is the case, the Z center will show either
+220 (extended) or -220 (retracted), respectively.
•
Drift in the optical path
Differentiating between optical path or mechanical drift is the
fi
rst step in eliminating this problem.
The force curve is a very useful tool for this purpose. Go to the force curve immediately after
engaging. The force curve has two main regions: the sloping regions when the sample is in contact
with the tip, and the
fl
at region when the tip is free. Intersection of these two regions is what is
important. Watch the force curve and determine whether the curve drifts vertically or horizontally;
