Realtime Operation
Rev. F
Scanning Probe Microscope Training Notebook
39
The Scan Rate setting will greatly depend on the scan size and the height of the features being
imaged. In general, the taller the features and/or the larger the scan size, the slower the scan rate.
Typical Scan Rate settings are 0.5 to 2.0Hz for TappingMode and 1 to 4Hz for Contact Mode.
16.4 Other Important Parameters
Scan Size
: Adjusts the size of the X,Y scan area
X Offset, Y Offset
: Translates the scan area in X and Y directions without changing scan size
Note:
The
Zoom
and
Offset
commands found on the display monitor may also be
used to change the scan size and X and Y offsets.
Scan Angle
: Controls the angle of the fast scan direction of the scanner with respect to the X axis
Samples/line
: Determines the number of data points or pixels in X and Y (128, 256, or 512)
Slow Scan Axis
: Enables and Disables movement of the scanner in the direction of the slow scan
axis. (Y direction at 0° Scan Angle)
Proportional Gain
: Controls the amount of proportional error signal used in feedback calculation.
Typically set 30 to 100% higher than the Integral Gain
Data Type
: Selects the signal viewed on the display monitor - this parameter is set to Height for
topographical measurements
Line Direction
: Selects the direction of the fast scan during data collection: Trace (left to right) or
Retrace (right to left).
Microscope Mode
: Sets mode of operation to Tapping, Contact, or Force Mod
Data Scale
: Controls the vertical scale of the full height of the display and color bar. This
parameter does not effect the Realtime operation of the microscope, only the expansion and
contraction of the color scale.
Z-limit
: Allows the 16 bits of the digital-to-analog converters to be applied to a smaller vertical
range. This has the effect of increasing the vertical sampling resolution and should be used for
imaging very smooth surfaces (<5nm RMS) or performing atomic resolution.
•
For example, a Dimension or J MultiMode scanner may have a full vertical movement
of 6µm over 440V. By reducing the Z-limit to 55V, the full vertical movement of the
scanner is reduced to 0.75µm over the same 16 bits. Therefore, the vertical sampling
size becomes smaller, which increases the Z resolution.
Note:
Do not reduce the Z-limit if there is a chance that a feature will exceed the
reduced vertical range.