Force Imaging
Force Modulation
208
MultiMode SPM Instruction Manual
Rev. B
Figure 11.6d
Typical Frequency Sweep Plot
Note:
The large drive amplitude is necessary because peaks are smaller than normally
seen during TappingMode operation. This is due to the cantilever not at
resonance; therefore, its motion is mostly vertical. Vertical motion is not
ampli
fi
ed by the beam de
fl
ection detection technique which is sensitive
primarily to changes in cantilever angle.
f.
Adjust the
Sweep width, Data scale
and the
Drive amplitude
until you can clearly see
peaks. Bimorph resonances typically occur between
8
-
20kHz
.
g. Choose a peak, then click on the
Zoom In
command (top menu bar of display monitor)
with the left mouse button. Two vertical lines appear on the
Frequency Sweep
plot.
h. Use the mouse to move the vertical lines until the selected peak is centered between the
lines.
i.
Increase or decrease the zoom range by clicking the left mouse button.
j.
When the peak centers and the zoom width is adjusted, double-click the right mouse
button to automatically adjust the
Drive Frequency
and
Sweep width
, and zoom in on
the selected peak.
k. Use the
Offset
command on the display monitor to center the peak in the graph. Click
on the
Offset
command with the left mouse button; a vertical, green line appears on the
plot.
l.
Move the line until centered on the desired peak (usually the frequency with the highest
amplitude), then double-click the left button to lock it.
m. Click
Execute
. The computer automatically changes the
Drive Frequency
so that the
peak is centered. You may need to click on this command more than once to properly
center the peak.
Note:
Once you choose the desired frequency, the
Frequency Sweep
plot should be
recentered similarly to the plot shown in (see
).
Peaks due to bimorph
Peaks due to cantilever
