Force Imaging
Force Modulation
236
Dimension 3100 Manual
Rev. D
4. Install the cantilever holder on the Dimension SPM head.
5. Align the laser on the cantilever.
Note:
Methods for aligning the laser are discussed in
6. Adjust the
Setpoint
. Begin with a
Setpoint
of
0V
. Recall that higher setpoints cause the
cantilever to push harder on the surface during scanning.
7. Turn the photodetector adjustment knobs to center the laser spot on the laser detector. Adjust
the
Vertical Deflection
to approximately -
0.5V
for FESP or TESP cantilevers, -
2V
for NP
cantilevers.
Note:
The force the cantilever applies to the surface is related to the difference
between the
Vertical Deflection
and the
Setpoint
and the spring constant of the
cantilever used. If the sample is very delicate, set the
Vertical Deflection
value
closer to the chosen
Setpoint
.
8. Find the
Bimorph Resonant Frequency
: The cantilever is oscillated by a small
piezoelectric bimorph mounted in the cantilever holder. For
Force Modulation
, oscillate the
bimorph at or near its resonant frequency. The bimorph resonance frequency is usually the
largest peak in the 5-30kHz range. This ensures the cantilever moves with sufficient
amplitude to produce elasticity contrast.
Note:
You need to find the bimorph’s resonant frequency only once. (Resonant
frequencies are unique to each force modulation cantilever holder.) Once you
find the resonant frequency, write it down for future use. This
Drive frequency
may be used as a starting place each time you perform force modulation
imaging; however, recheck the bimorph’s resonant frequency in free air using
Cantilever Tune
each time you install a new cantilever.
a.
Use a FESP or TESP cantilever. NP probes have confusing low frequency resonances.
b. Select
View
>
Sweep
>
Cantilever Tune
or click on the
Cantilever Tune
icon.
c.
The display monitor plots the
Frequency Sweep
, showing cantilever oscillation
amplitude versus frequency. To set the parameters controlling the
Frequency Sweep
plot, use the parameters in the
Sweep Controls
panel and the commands on the top
menu bar of the display monitor.
Содержание Dimension 3100
Страница 12: ...xii Dimension 3100 Manual Rev D ...
Страница 20: ...List of Figures xx Dimension 3100 Manual Rev D ...
Страница 72: ......
Страница 106: ......
Страница 118: ......
Страница 214: ...Scanning Tunneling Microscopy STM Etching Tungsten Tips 194 Dimension 3100 Manual Rev D ...
Страница 222: ......
Страница 266: ......
Страница 274: ......