Maximize The Sum Signal; Figure 5.2D Signals Produced By The Photodetector Are Optimized Using The Head's - Veeco 004-210-000 Instruction Manual

Head, Probe and Sample Preparation
Laser Alignment

5.2.3 Maximize the SUM Signal

This section describes what to do after the laser spot is aligned on the cantilever and assumes
knowledge of how to read voltages from the meters mounted on the front of the MultiMode base. If
you are unfamiliar with reading the MultiMode voltage meters, skip ahead to MultiMode SPM
Voltage Meters: Section 5.4, then return to this section. Additional information is provided in each
of the various chapters on imaging.
After the laser beam is aligned on the tip of the cantilever using one of the methods described
above, move the mirror lever on the back of the head (Figure 5.2d) to maximize the SUM signal.
Next, adjust the photodiode positioner to set the output signal to the desired value.
Figure 5.2d Signals Produced by the Photodetector are Optimized using the Head's Various Adjustments
Photodetector mirror adj.
A-B signal
Tipholder clamping screw
Photodetector mirror lever
Y-axis X-axis
(Front-Top View)
Photodetector mirror adj.
C-D signal
(Rear View)
This adjustment is much less sensitive than the laser position adjustments. The maximized sum
signal should be approximately 4.0 - 9.0V for silicon nitride cantilevers. The value of this signal
varies with many factors. It is important to note that it is possible to see a large response on the bar
graph without having the laser beam on the cantilever, so it is important to visually verify that the
laser beam is on the cantilever and not rely on the bar graph alone. Attempting to engage with the
laser beam improperly aligned will usually destroy the cantilever and may damage the sample.
Rev. B MultiMode SPM Instruction Manual 83