Infusion Doping of Tunnel Junctions

Abstract

One of the problems confronting the experimenter who wishes to study organic monolayers by electron tunneling is that of introducing organic molecules into the tunneling structure. The descriptive term “doping” will be used to describe this process. As can easily be seen from other chapters in this book and from a study of the literature in this field,(1–6) organic molecules with a wide variety of properties are studied by electron tunneling, and several doping techniques have evolved to accommodate them. To be successful the technique must achieve a stable coverage of one monolayer or less inside the tunnel junction. The doping procedure must not cause unwanted chemical changes in the deposit such as decomposition due to heating or reaction with the chamber walls. Impurities must be excluded and the deposited monolayer must be stable during the remaining fabrication steps. Hope has been placed in the possibility that tunneling spectroscopy will become a routine tool for analysis of monolayers of organics. Since taking the spectra from a prepared tunnel junction is relatively easy to do, it remains for junction fabrication and doping techniques to develop to the degree that junctions can be prepared and doped easily and under a wide variety of conditions of interest to the surface chemist.