Biomedical Engineering Reference
In-Depth Information
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Fig. 6.11. Edge overshoot in the z axis. Top: the probe is scanned from left to right across a feature
on a surface; overshoot may be observed in the line profile at the leading and trailing edge of the
features. Bottom: the AFM image of a test pattern appears to have no artefacts at first glance (left),
but a line profile of the test pattern shows overshoot at the top of each of the lines (right, overshoot
arrowed).
Fig. 6.12. Scanner drift cause and effect. Left: creep in piezoelectric scanners causes the scanner to
keep moving even after the applied voltage stops changing. Right: the effect on AFM images is most
often seen as a distortion in the beginning of the scan (here, scanning from the top).
distortion. Alternatively, the instrument can be set to do a continuous line scan in the new
position. When the user observes that the features in the line scan are no longer changing,
the drift has stopped and the image scan should then be begun.
6.2.6 Z angle measurements
Mechanical coupling between the piezoelectric ceramics that move the probe in the x or
Y directions and the Z direction can cause substantial errors when trying to measure
vertical angles with the AFM. This sort of crosstalk is common in piezoelectric tube
scanners, and means that the accuracy of angles in the Z axis measured with most AFMs
 
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