Instruction manual
Electric Force (EFM) Imaging
Surface Potential Imaging—Procedure
266 MultiMode SPM Instruction Manual Rev. B
Table 14.7a Basic Extender Module toggle switch settings for surface potential imaging.
Note: The toggle switch combination of Surface Potential = ON and Analog2 = ON is
not recommended and can produce erratic and undefined results.
2. Mount a sample onto the sample holder. Make any external electrical connections that are
necessary for the sample.
3. Mount a metal-coated NanoProbe cantilever into the electric field cantilever holder. MFM-
style cantilevers (225µm long, with resonant frequencies around 70kHz) usually work well.
It is also possible to deposit custom coatings on model FESP silicon TappingMode
cantilevers. Verify that all deposited metal adheres strongly to the silicon cantilever.
4. Set up the AFM as usual for TappingMode operation.
5. Use Cantilever Tune: AutoTune (as described in Step 6 of Section 14.4) to locate the
cantilever resonant peak. Remember, however, that the Extender box has been reconfigured
so that the phase detection circuitry now acts as a lock-in amplifier. Any procedures that are
normally used to view or adjust the phase signal will now affect the lock-in signal instead
(see Figure 14.5a).
In this case, two curves should appear in the Cantilever Tune box: the amplitude curve in white
and the lock-in curve in yellow. In the event you find more than one resonance, select a resonance
that is sharp and clearly defined, but not necessarily the largest. It is also helpful to select a resonant
peak where the lock-in signal also changes very sharply across the peak. Multiple peaks can often
be eliminated by making sure the cantilever holder is clean and the cantilever is tightly secured.
6. Engage the AFM and make the necessary adjustments for a good TappingMode image while
displaying height data.
Mode Tip or Sample Voltage
FM/Phase Surface
Potential
GND/Surface
Potential
Analog 2
TappingMode
Contact AFM
MFM
√ √
Surface
Potential
√ √
Apply voltage
to tip or sam-
ple (Use for
electric field
gradient
imaging; tun-
neling AFM)
√ √