Kelvin Probe Microscopy

Scanning probe microscopy methods allow investigating a variety of sample surface properties on a nanometer scale, even down to single molecules. As molecular electronics advances, the characterization of electrical properties becomes more and more important. In research and industry, films made from composite materials and lithographically structured elements have already reached structure sizes down to a few nanometers. Therefore electrical modes play an increasing role for material characterization.

Kelvin probe force microscopy (KPFM) is sensitive to local variations in the work function of materials. The work function depends on the specific material, adsorption layers (e.g. water), oxide layer thickness, dopant concentration, electrostatic charges, surface dipole moments and temperature. Thus the KPFM mode becomes useful to study surfaces made from different materials, e.g. polymer blends, composite materials. Furthermore functional materials and devices (e.g. solar cells) can be investigated which respond to light or to vapours. In order to study light induced charging of surfaces (e.g. solar cells) we have build up a photo-sensitive scanning force microscope which is situated in an environmental chamber (see Figure 1).

Figure 1: in the photosensitive scanning probe microscope, two types of sample illumination are available: white light (top) and laser light at 488 nm (bottom).
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