SCANNING-TUNNELING-MICROSCOPY OF CHAIN-MOLECULES AT SOLID-FLUID-LNTERFACES

Scanning tunneling microscopy has been employed to investigate chain m olecules, which have been self-assembled at the interface between thei r melts or organic solutions, and a solid hat surface of a semimetal o r a semiconductor. Also it has been used to observe chain molecules in a precursor wetting layer in the vicinity of the edge of a solidified alkane melt drop. With a resolution in space and time of 10 pm and 10 mu s, respectively, it is possible to investigate (i) commensurabilit y between substrate and adsorbate lattices, (ii) the packing of molecu les and molecular mixtures with various symmetries on several structur ally and chemically different substrates, (iii) temperature and compos ition induced order-disorder transitions between 2-dimensional crystal s and liquid crystals, and (iv) the current through individual molecul ar segments at different bias voltages. We summarize some of our work in this area, and report on new results on an alkoxylated poly(p-pheny lene) on the basal plane of highly oriented pyrolytic graphite (HOPG).