Force Imaging
Force Calibration (TappingMode)
228
Dimension 3100 Manual
Rev. D
13.5 Force Calibration (TappingMode)
Force Mode
allows the imaging of forces between the tip and surface, including chemical bonds,
electrostatic forces, surface tension and magnetic forces. In TappingMode, you can observe forces
by measuring changes in tip RMS amplitude, phase, or TM deflection. The user may collect force
plots in one of two forms:
Force Plot
and
Force Volume
. The two forms are similar, with
Force
Volume
generating a map of many individual force plots. To produce high-quality force plots, it is
necessary to precisely control tip position relative to the surface.
13.5.1 Force Plots
When performing
Force Plot
in TappingMode, the piezo moves to the center of the current X-Y
scan, then turns off the X-Y scan motion. Next, a triangular waveform is applied to the Z electrodes
of the piezo tube resulting in the oscillating tip moving up and down relative to the sample. The
same Z-axis piezo motion occurs in Contact Mode AFM force plots. However, in TappingMode,
the force plot is a graph of the piezo’s extension versus oscillating tip amplitude, phase or TM
deflection, instead of deflection or friction.
Uses of
Force Calibration
in TappingMode include characterizing forces on the cantilever tip,
diagnosing SPM performance, calibrating the RMS amplitude or TM deflection, and configuring
Lift
Mode
. For example, as the oscillating tip is brought closer to the surface, tip motion is
dampened, which shows as an immediate drop in amplitude. When plotted, the graph resembles
CAUTION:
Because TappingMode cantilevers are relatively stiff,
Force Mode
can potentially damage the tip and/or surface. Before using Force
Calibration, read and understand the following section.
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