Film thickness measurement and linear dichroism of organic thin films prepared by molecular beam deposition at oblique incidence

Linear dichroism - the in-plane optical anisotropy - is observed for organi c thin films grown on fused silica and glass substrates. The films made of [4-pyrid-4-yl-ethynyl-benzoic acid] and [4-trans-2-(pyrid-4-yl-vinyl) benzo ic acid] are deposited from an angle of about 30 degrees with respect to th e surface normal under ultra-high vacuum conditions. The film thickness mea surements by alpha-step, atomic force microscopy in tapping mode, and in si tu ellipsometry as well as transmission spectra are discussed in detail. Mo reover, the optical constants of these novel materials are determined using ellipsometry and transmission spectroscopy. The remarkable optical asymmet ry is found in the ultra-violet transmission spectra and attributed to orie nted molecules which are connected by hydrogen bonds. (C) 1999 Elsevier Sci ence B.V. All rights reserved.