Molecules at interfaces: STM in materials and life sciences.

The scanning tunneling microscope (STM) enables us, for the first time, to directly observe individual molecules both at surfaces under ultrahigh-vacuum conditions as well as at interfaces with fluids or soft solids. In suitable systems, structure and dynamics of single molecules or monomolecular layers can be investigated at a resolution down to the atomic length scale and the time scale of milliseconds. The structure of individual biopolymers and biological membranes on solid supports can be studied on the nanometer scale. Furthermore, the STM may be viewed as a tool to address individual molecules, e.g., for molecular electronics studies or the manipulation of individual molecular structures. The paper reviews selected STM results on organic conductors, as well as small organic molecules and large biopolymers, which have been chemi- or physisorbed to conducting substrates. Finally, some prospects for future work are discussed.