Contact AFM Mode
Initiate the Engage Command
Rev. B
MultiMode SPM Instruction Manual
95
6.3
Initiate the Engage Command
Select
Motor
>
Engage
(or click the
Engage
icon). A pre-engage check, followed by Z-stage
motor sound should be observed. If for any reason the engage aborts because the SPM head is still
too far away from the surface, click on the
Abort
button and readjust the screws to start the tip
closer to the sample surface. Assuming the tip is better positioned before engaging again, an image
should begin to appear on the image monitor.
After good engagement is obtained, gradually reduce the setpoint offset (disengage-minus-setpoint)
to give a smaller contact force. A large offset between the setpoint and disengaged signal is
recommended during a
fi
rst try, because sometimes there are dif
fi
culties in engagement that can be
reduced with a larger offset. On subsequent engagements, try smaller signal offsets as con
fi
dence in
use of the instrument is gained.
6.3.1 Adjust Setpoint with Force Calibration
The most accurate way to minimize the
Setpoint
value is by using Force Calibration (
Realtime
>
View
>
Force Mode
>
Calibration
). This consists of obtaining a force plot, then adjusting the
Setpoint
value until the tip almost pulls free of the surface. In this way, it is possible to minimize
tip-sample forces and reduce wear on both the tip and surface.
Getting a good Force Calibration plot
Force plots are discussed in detail in
of this manual. For standard force calibration plots,
start with the following parameter values:
Panel
Parameter
Setting
Z Scan Controls
Scan Size
500 nm —1
µ
m
a
a. A good Z-axis scan size is from 500 nm to 1µm. Scans larger than 1µm may
diminish details and make them hard to see. Scans smaller than 500nm may
be too small and make it dif
fi
cult to pull the tip clear of the surface.
X offset
0.00 nm
Y offset
0.00 nm
Scan angle
0.00 deg
Scan rate
9.00 Hz
Number of samples
512
Average count
1
Display mode
Both
Trigger mode
Off
Start mode
Calibrate
Channel 1
Data type
De
fl
ection
Z range
(Set to maximum)
