
Magnetic Force Microscopy
Troubleshooting
270 Dimension 3100 Manual Rev. D
Note: This step is not necessary for NanoScope IV.
5. Click the Ok button when complete.
15.6 Troubleshooting
15.6.1 MFM Image Verification
The procedure described above should produce a good magnetic force gradient image of the
videotape sample. If there is a problem, check that the Interleave Mode is set to Lift, that Interleave
is Enabled and that the Scan Line is set to Interleave. Check also that the Interleave values of
Drive Amplitude and Drive Frequency are initially set equal to the main Scan Controls values.
15.6.2 Saturation in Amplitude Detection
If using amplitude detection, the magnetic force image can saturate (appear completely featureless)
if the Interleave Drive Amplitude is significantly different than the Drive Amplitude in the main
scan. Adjust the Interleave Setpoint to restore the image.
Note: The Interleave Setpoint has no physical effect in LiftMode since there is no
surface feedback during the lift pass.
15.6.3 Optical Interference
When using Amplitude Detection, optical interference may sometimes appear in the Lift
(magnetic force gradient) image when imaging highly reflective samples. Optical interference
appears as evenly spaced, sometimes wavy lines with ~1–2µm spacing superimposed on the lift
image. This occurs when ambient laser light (i.e., light passing around or through the cantilever,
then reflecting off the sample) interferes with laser light reflecting from the cantilever. Interference
can be alleviated by moving the beam spot up the cantilever away from the tip; one-third of the
cantilever length works well. The adjustment can be refined by carefully moving the beam spot
laterally a small distance on the cantilever while scanning until interference fringes are minimized.
Be careful not to move the beam off the cantilever or feedback may be lost.
Note: Optical interference is essentially eliminated by using phase detection or
frequency modulation.
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