Nanosurf easyScan 2 AFM, Operating Instructions Manual

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AFM Theory
Scanning Probe Microscopy
The easyScan 2 AFM is an atomic force microscope, which is part of the
family of scanning probe microscopes. When the first scanning probe
microscope, the scanning tunneling microscope (STM), it became possible
to look into the fascinating world of atoms. The STM was developed by
Gerd Binnig and Heinrich Rohrer in the early 80’s at the IBM research
laboratory in Rüschlikon, Switzerland. For this revolutionary innovation
Binnig and Rohrer were awarded the Nobel prize in Physics in 1986.
However, the STM technique is restricted to electrically conducting sur-
faces. A further development of the STM called the Atomic Force Micro-
scope (AFM) was developed by Gerd Binnig, Calvin Quate and Christoph
Gerber. The AFM extended the abilities of the STM to include insulating
material. Both the AFM and the STM microscopy techniques work with-
out optical focusing elements. Instead, a small sharp probing tip is scanned
very closely across the sample’s surface. The distance between the tip and
the sample surface is so small that atomic-range forces act between them. In
an AFM, tip is attached to the end of a cantilever in order to measure these
forces. The force acting on the tip can then be determined by detecting the
deflection of this cantilever.
The measurement of the cantilever deflection can be used to control the tip-
surface distance on an atomic scale. Thus, enormous resolution can be
achieved, so that even the atomic arrangement of surfaces can be probed.
This measurement is a so-called static measurement mode, in which the
static deflection of the cantilever is used. Generally, the forces acting on the
tip will cause it to snap onto the sample, which result in an effective, nano-
meter-range flattening of the tip, and friction and stiction between the tip
and the sample.
To circumvent the aforementioned problems, the so-called Dynamic force
microscopy modes can be used, as was pointed out by the AFM’s inventors.
The cantilever vibrates during the operation in these measurement modes.
In the dynamic modes, changes in the free resonance frequency and the