Electrical modes in scanning probe microscopy

Scanning probe microscopy methods allow the investigation of a variety of sample surface properties on a nanometer scale, even down to single molecules. As molecular electronics advance, the characterization of electrical properties becomes more and more important. In both research and industry, films made from composite materials and lithographically structured elements have already reached structure sizes down to a few nanometers. Here, we review the major scanning probe microscopy modes that are used for electrical characterization of thin films, that is, scanning conductive force microscopy, Kelvin probe force microscopy and scanning electric field microscopy. To demonstrate the possibilities and capabilities of these modes, reference samples were fabricated by means of focused ion beam deposition and analyzed using the described methods. Furthermore, two upcoming modes are presented that are based on: i) local current measurements while the SPM-cantilever is excited into torsional vibrations, and, ii) changes in a backscattered microwave that was coupled into a scanning probe microscopy-cantilever. The scanning-probe-based electrical modes are applicable for studies of functional layers used in soft matter electronic devices under realistic environmental conditions.