REACTIVE GRAPHITE ETCH AND THE STRUCTURE OF AN ADSORBED ORGANIC MONOLAYER - A SCANNING TUNNELING MICROSCOPY STUDY

Two types of surface interactions of the basal plane of graphite with an organic ambient have been investigated with the scanning tunneling microscope: (1) At the bulk interphase between octylcyanobiphenyl and graphite local surface reactions have been observed with a threshold tip bias of — 1.7 V and lifetimes of the reaction products on the order of 1 s. At more negative bias between — 2.5 and — 4 V the reactions become more intense resulting in localized graphite etch. While a crystalline adsorbate phase of octylcyanobiphenyl is very rarely observed on the flat graphite surface, it occurs more readily after the etching procedure, indicating a lack of nucleation sites on the pristine graphite. (2) A monolayer of a mixed cellulose ether (laurylmethyl) transferred onto graphite by the Langmuir-Blodgett technique has been imaged in the tip bias range of + 10 mV to + 1 V with a resolution of better than 1 nm. From the images one can determine the conformation of the individual polymer molecule. The polymer is found to be extended over several tens of nanometers and characteristic kinks along the chain are observed, indicative of a conformation which results from the adsorption of a twisted ribbon. © 1990, American Vacuum Society. All rights reserved.