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-deposited o n friction-transferred polytetrafluoroethylene (PTFE) substrates was invest igated by optical and electron microscopy and electron diffraction. Highly birefringent 6T films are formed at high or low deposition rates. Electron diffraction indicates the presence of three different crystal populations d iffering by the orientation of the 6T molecular axis and/or the molecular p lant. First, the strongest substrate/deposit interactions are based on epit axy and lend to a well-defined, symmetric molecular arrangement (type I) wi th the 6T molecular and the PTFE chain axes parallel and the 6T molecular p lanes tilted at +/-33 degrees to the substrate. Second, more 'defective' or ientations result from interactions with the hare glass surface (type II) a nd with the PTFE film edges or ridges (type III), respectively. As shown in a parallel study using spectroscopic techniques, these defective orientati ons have a definite impact on the overall optical properties of the sexithi ophene thin films. (C) 1998 published by Elsevier Science S.A. All rights r eserved.