SCANNING-TUNNELING-MICROSCOPY STUDY OF ORIENTED POLY(TETRAFLUOROETHYLENE) SUBSTRATES

Highly oriented molecular structures of organic molecules are important in many applications of thin films and interfaces. Recently, it has been shown that poly(tetrafluoroethylene), or PTFE, can be deposited mechanically to form highly oriented thin films on glass substrates. Such oriented PTFE films can in tum be used as substrates for growth of ordered films of organic molecules and polymers, e. g. conjugated polymers. Despite the fact PTFE is electrically insulating, we have been able to use scanning tunneling microscopy (STM) to examine details of oriented ultrathin PTFE films deposited on various substrates, in particularly Pt and highly ordered pyrolytic graphite (HOPG). Ordered structures originating from aligned chains were observed, and reproducible images were obtained at the submicron level. Nanometric molecular details are more difficult to resolve, but indicate interesting features. In particular, we have observed regions of parallel zig-zag shaped molecules, which are separated by approximately 6 angstrom.