Properties of vacuum tunneling currents: Anomalous barrier heights
by J. H. Coombs, J. B. Pethica
A design of STM which does not use vacuum internal vibration isolation and may be cooled to liquid helium temperatures is described. Tunneling current characteristics underlying STM operations are discussed. A model is presented to explain the anomalously low (<1 eV) tunneling barrier heights often observed. On the basis of this model we suggest criteria for obtaining reliable STM images.