SEXITHIOPHENE THIN-FILMS EPITAXIALLY ORIENTED ON POLYTETRAFLUOROETHYLENE SUBSTRATES - STRUCTURE AND MORPHOLOGY (VOL 303, PG 207, 1997)

The structure and morphology of sexithiophene thin films vacuum-deposi ted on friction-transferred polytetrafluoroethylene (PTFE) substrates was investigated by optical and electron microscopy and electron diffr action. Highly birefringent 6T films are formed at high or low deposit ion rates. Electron diffraction indicates the presence of three differ ent crystal populations differing by the orientation of the 6T molecul ar axis and/or the molecular plane. First, the strongest substrate/dep osit interactions are based on epitaxy and lead to a well-defined, sym metric molecular arrangement (Type I) with the 6T molecular and the PT FE chain axes parallel and the 6T molecular planes tilted at +/- 33 de grees to the substrate, Second, more ''defective'' orientations result from interactions with the bare glass surface (Type II) and with the PTFE film edges or ridges (Type III), respectively. As shown in a para llel study using spectroscopic techniques, these defective orientation s have a definite impact on the overall optical properties of the sexi thiophene thin films. (C) 1997 Elsevier Science S.A.