Electric Force (EFM) Imaging
Electric Field Gradient Detection—Procedures
Rev. B
MultiMode SPM Instruction Manual
257
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. Make sure that any deposited metal you use adheres strongly to the silicon
cantilever.
4. Set up the AFM as usual for TappingMode operation. In the
Channel
panels, be certain all
Highpass
and
Lowpass
filters are
Off
. Set the
Rounding
parameter in the
Microscope
>
Calibrate
>
Scanner
window to zero (0.00).
5. Select
View
>
Cantilever Tune
.
6. Follow the instructions below for the type of electric force imaging desired,
Phase Detection
or
Amplitude Detection
.
14.4.1 Phase Detection
Phase Detection is only available when the Basic Extender Module has been correctly con
fi
gured
into the system.
•
In the
Cantilever Tune
window, set
Start frequency
and
End frequency
to appropriate
values for your cantilever (e.g., for 225µm MFM cantilevers, set
Start frequency
to
40kHz and
End frequency
to 100kHz). Select
Autotune
.
•
Two curves appear on the Cantilever Tune graph: the
amplitude
curve in white, and the
phase
curve in yellow. (In
phase
curve is the dashed line and the
amplitude
curve is the solid line).
Figure 14.4b
Phase detection
Cantilever Tune
(for systems
with
the Basic Extender Module installed)
The phase should decrease with increasing frequency and cross the center line (90° point) at the
peak frequency. The phase curve then correctly re
fl
ects the phase lag between the drive voltage and
the cantilever response. Again, gradients in the electric force will cause a shift
∆
F
0
in the resonance
frequency. In this case, resonance shifts give rise to phase shifts
∆
φ
which can then give an image of
the electric force gradients; see
.
