Force Imaging
Force Modulation
Rev. B
MultiMode SPM Instruction Manual
209
n. Adjust the
Drive amplitude
so the maximum response amplitude is about
1V
. Recenter
the peak if necessary.
Figure 11.6e
Correctly Tuned Force Modulation Frequency
Note:
You may also change the
Drive Frequency
by clicking on the
Drive
Frequency
parameter on the control monitor’s
Feedback Controls
panel, and
entering a new value.
Note:
Bimorph resonance should be between
5 kHz
and
30 kHz
. If peaks are found at
a much higher frequency, these are cantilever resonances,
not
bimorph
resonances.
o. Record the
Drive frequency
. This is the resonant frequency of your force modulation
bimorph.
9. Bring the tip near the sample with the manual motor controls.
10. Check the scan parameters
Scan speed
,
Scan size
and
Integral gain
to verify they are
reasonable for Contact Mode AFM imaging. Also, it may be desirable to readjust the detector
mirror adjustment screws if the
Vertical Difference
signal has drifted from the value
originally set.
11. For the
Channel 1
image, select
Data Type
>
Height
. Select
Data Type
>
Amplitude
for
the
Channel 2
image. The multi-image capability views both the topography data and the
force modulation (elasticity) data at the same time.
12. Reduce the
Drive Amplitude
to
0
before engaging.
13. Select
Motor
>
Engage
.
Note:
The motor moves the SPM head down towards the sample and stops once the
cantilever de
fl
ects to the chosen
Setpoint
. Under some conditions the system
may “false engage” before the cantilever actually reaches the surface. Increase
the
Setpoint
and engage again.
020
