Piezoelectric Scanners: Creep and Bow
Rev. F
Scanning Probe Microscope Training Notebook
19
9.0
Piezoelectric Scanners: Creep and Bow
9.1 Creep
Creep is the drift of the piezo displacement after a DC offset voltage is applied to the piezo.
This may occur with large changes in X & Y offsets, and when using the frame up and frame down
commands when the piezo travels over most of the scan area to restart the scan.
When a large offset is performed, the scanner stops scanning and a DC voltage is applied to the
scanner to move the requested offset distance. However, the scanner does not move the full offset
distance all at once. It initially moves the majority of the offset distance quickly, and then slowly
moves over the remainder. The scanning resumes after a majority of the offset distance has been
moved although the scanner is still slowly moving in the direction of the offset. Creep is the result
of this slow movement of the piezo over the remainder of the offset distance once scanning has
resumed.
Creep appears in the image as an elongation and stretching of features in the direction of the offset
for a short period of time after the offset.
Figure 9.1a
Calibration Grating
An example of creep is shown in the image of a calibration grating (see
). The tip was
scanning from top to bottom and an offset of 10µm in the X direction was performed near the
beginning of the scan (indicated by the arrow). The slight bending of the lines which occurs directly
after performing the offset are due to creep. The creep settles out by the end of the scan.
When creep appears in the image, it will often settle out by the end of the scan and the next image
may be captured. For very large offsets (>50µm), it may take longer than 1 scan for the creep to
settle out. The creep can be reduced by offsetting beyond the desired point and then offsetting back
to the desired point.
