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Electric Techniques
Electric Force Microscopy
Rev. D
Dimension 3100 Manual
293
16.2.5 Frequency Modulation
For more quantitative results, use frequency modulation (FM). This technique provides a direct
measure of change in resonant frequency sensed by the cantilever.
1. Follow all the steps required to perform phase detection EFM.
2. In the
Interleave Controls
panel, set the
Input feedback
to
Frequency
.
3. Switch the
Data Type
for
Channel 2
to
Frequency
.
Note:
It may be necessary to optimize the FM gains in the
Other Controls
panel to
properly track the shifts in resonant frequency (starting values:
FM
igain
=
40
and
FM
pgain
=
60
).
Note:
For NanoScope software versions 4.23 and lower, there is no
Input feedback
setting; just switch the
Data Type
for
Channel 2
to
Frequency
.
16.2.6 Amplitude Detection
Amplitude detection is inferior to the phase and frequency detection methods described previously
and is not the recommended technique for systems with an Extender Electronics Module.
Amplitude detection is the only technique available for systems without the Extender Electronics
Module. This section describes the differences in set up for amplitude detection. Changes in the
cantilever amplitude provide an
indirect
measure of shifts in the cantilever resonance frequency as
shown in
Figure 16.2q
Shift In Amplitude at Fixed Drive Frequency
1. Set the
Drive frequency
to the left side of the cantilever resonance curve, as shown in
Drive Frequency
Amplitude
∆
F
0
∆
amplitude
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