User`s guide

Introduction to the Agilent 5500 1
Agilent 5500 SPM User’s Guide 22
detector. As the cantilever bends, the position of the laser spot changes.
The resulting signal from the detector is the Deflection, in volts. The
difference between the Deflection value and the user-specified Set Point
is called the “error signal.”
Figure 5 Basic AFM principles
Figure 6 shows the force interaction as the tip approaches the sample. At
the right side of the curve the tip and sample are separated by large
distance. As they approach, tip and sample atoms first weakly attract
each other. This zone of interaction is known as the “non-contact”
regime. Closer still, in the “intermittent contact” regime, the repulsive
van der Waals force predominates. When the distance between tip and
sample is just a few angstroms, the forces balance, and the net force
drops to zero. When the total force becomes positive (repulsive), the
atoms are in the “contact” regime.The various AFM techniques