QUANTITATIVE SCANNING TUNNELING MICROSCOPY AND SCANNING FORCE MICROSCOPY OF ORGANIC MATERIALS

The capabilities and limitations of scanning tunneling microscopy and scanning force microscopy for a quantitative characterization of organic materials are discussed. Resolution in space and time, as well as measurements of electronic properties and forces are analyzed for three classes of systems, i.e. (i) molecular monolayers on atomically flat conductive supports, which are thin enough to allow electron tunneling through them, (ii) protein layers with a. metallic overcoat, and (iii) native proteins or other macromolecules on electrically insulating substrates. In particular, we suggest criteria to define lateral resolution, which are not exclusively based on the ratio of signal to noise, as usually exploited in transmission electron microscopy.