Introduction to the Keysight 5500
5
Keysight 5500 SPM User’s Guide
5-8
described below, can be generally described by their function within
these three domains.
Figure 1-6
Zones of interaction as the tip approaches the sample
The tip-sample interaction is complicated by additional forces,
including strong capillary and adhesive forces that attract the tip and
sample. The capillary force arises when water, often present when
imaging in the ambient environment, wicks around the tip, holding the
tip in contact with the surface. As long as the tip is in contact with the
sample, the capillary force should be constant because the fluid between
the tip and the sample is virtually incompressible. The total force that
the tip exerts on the sample is the sum of the capillary, adhesive and van
der Waals forces.
The van der Waals force counters almost any force that attempts to push
the atoms closer together. When the cantilever pushes the tip against the
sample, the cantilever bends rather than forcing the tip closer to the
sample atoms. The deflection, therefore, can be used as a reliable
indicator of surface topography.
Contact Mode AFM
In Contact Mode AFM, the AFM tip is attached to the end of a
cantilever with a low spring constant (typically 0.001 - 5 nN/nm). The
