Instruction manual

TappingMode AFM
Preparation Prior to Imaging
Rev. B MultiMode SPM Instruction Manual 107
7.2.4 Adjust Laser and Photodetector
Verify that the tipholder has been fitted with a TappingMode, single crystal silicon probe and
aligned per instructions provided in Chapter 5 of this manual. Photodetector voltage values are
displayed on meters mounted on the front of the MultiMode base. The laser photodetector is
adjusted using the photodetector adjustment knobs on the left-top and left-rear of the head (see
Figure 7.2c below). Recall that RMS amplitude is an AC signal which does not have any real
meaning until cantilever tuning is completed (see Section 7.2.5). The laser spot will need to be
approximately centered prior to entering the Cantilever Tune routine.
Figure 7.2c Photodetector adjustment knobs and SPM voltage meters.
Photodetector output
signal (RMS AC volts).
This value is directly
influenced by the
Drive amplitude
Deflection voltage. This
changes according to
how beam is centered
vertically. At 0.00 Volts
beam is centered.
Sum signal. This
value changes
according to how
much of the beam
falls on the
photodetector.
parameter when tip
is at resonance.
Photodetector adjust-
ment knobs.
VERT
SUM
0.26 0.00
4.0
RMS