Electric Force (EFM) Imaging
Electric Field Gradient Detection—Procedures
258
MultiMode SPM Instruction Manual
Rev. B
Figure 14.4c
Shift in Phase at Fixed Drive Frequency
•
Under Interleave Controls set the
Lift start height
to
0nm
, and
Lift scan height
to
100nm
. (The lift height can later be optimized.) Set the remaining Interleave parameters
(
Setpoint
,
Drive amplitude,
Drive frequency
, and gains) to the main Feedback
Controls values. This can be done by setting the
fl
ags (left of the Interleave Control
column) to “off” (grayed bullets). Set the
Analog 2
to
1V
(this will be optimized later).
•
Quit
Auto Tune
and return to
Image Mode
•
Engage the AFM and make the necessary adjustments to obtain a good topography
(
Height
) image on Channel 2.
•
Select the
Interleave Controls
panel. Set the
Setpoint
,
Drive amplitude
,
Drive
frequency
to Main (“off” grayed bullets). Verify that
Interleave scan
is set to
Lift
.
•
Choose a
Lift scan height
of
100nm
. This will be optimized later. Set the Channel 1
image
Data type
to
Phase
and choose
Retrace
for the scan
Line direction
on both
Channel 1 and 2 images.
•
Switch
Interleave mode
to
Enable
to start
LiftMode
. Set the Channel 1
Scan line
to
Interleave
to display interleave data. This screen should now display the cantilever
phase change due to electrical force gradients from the sample in the left image and
topography in the right image.
•
Optimize the
Lift height
. For high-resolution, make the
Lift scan height
as small as
possible without crashing the tip into the surface. If the tip crashes into the surface it
creates bright or dark streaks across the image. Also, if the
Lift scan height
is set
extremely low, the tip may continuously “tap” on the surface during the
LiftMode
scan.
Check this by toggling between the
Interleave
and main scan lines for the phase image.
The two images will look very similar if the tip is continuously tapping on the surface
during the
LiftMode
scan. In this case, increase the
Lift scan height
until the
Interleave
scan image abruptly changes, indicating that it is now oscillating above the
surface and not continuously tapping.
∆φ
Drive Frequency
90
0
180
Phase (deg)
∆
F
0
