Instruction manual

Magnetic Force (MFM) Imaging
Advanced Topics
238 MultiMode SPM Instruction Manual Rev. B
Setpoint
For the most reproducible results, it is best to use a consistent setpoint. In LiftMode, the total tip-
sample distance h
tot
is the sum of the average tip-sample distance in TappingMode h
T
, and the lift
scan height h
lift
(see Figure 13.6b). In TappingMode, the average tip-sample distance h
T
is equal to
the oscillation amplitude, which is determined by the setpoint. Large variations in setpoint can thus
change the total tip-sample distance in Liftmode, sometimes with visible results in the magnetic
image. For this reason, reproducible results are most easily obtained by using consistent setpoints.
Note that a lift scan height of 0nm still gives a mean tip-sample distance of h
T
in LiftMode.
Figure 13.6b Tip heights and oscillation amplitudes in TappingMode and LiftMode
The relationship between setpoint voltage and oscillation amplitude is known as the sensitivity. Its
value can be determined with Force Calibration; see Chapter 11 in the product instruction manual.
For 225µm MFM cantilevers, the sensitivity is typically in the range 15-20nm/V. A 1V Setpoint
typically corresponds to h
T
~15-20nm.
TappingMode pass
Lift pass
h
lift
h
T
h
tot
=
h
T
+ h
lift