Instruction manual

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 first try, because sometimes there are difficulties in engagement that can be
reduced with a larger offset. On subsequent engagements, try smaller signal offsets as confidence 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 Chapter 11 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
µm
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 difficult 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 Deflection
Z range (Set to maximum)