Biomedical Engineering Reference
In-Depth Information
pitch
Fig. A2. An example of a Z calibration standard (TGZ sample, images courtesy of Mikromasch).
These samples have a well-defined step height, enabling simple calibration of the Z axis sensitivity.
of the features. This is typically done with etched patterns in quartz or silicon. An example
is shown in Figure A3. Sometimes the specimen that is used for calibrating the Z axis can
be used for the X-Y axis as well. However, most specimens are accurate only in pitch or
step height. For very high-resolution calibration, any crystalline sample that can be
produced in atomic flatness and has a well-known lattice parameter could be used, but
mica and HOPG are the most convenient and commonly used. Table A2 lists some
available X-Y calibration specimens.
A3 XZ and YZ orthogonality
An AFM may be calibrated in X-Y and calibrated in Z and may not be useful for making
measurement of angles. This is because the XZ and YZ axis may not be orthogonal. The
reason for this is the crosstalk between the X-Y and Z axes as discussed in Chapters 2 and 6.
With the orthogonality references, this problem can be detected, and possibly corrected for.
This reference is fabricated by making a 1-D array, or line, of triangles in a silicon wafer,
see Figure A4.
Edge
step
length
pitch
Fig. A3. Example of a silicon X-Y calibration specimen (TGX grating, Mikromasch). Images
reproduced with permission from Mikromasch.
 
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