NEXAFS studies of copper phthaloyanine on Ge(001)-2 x 1 and Ge(111)-c(2 x 8) surfaces

A comparative investigation of the molecular orientation of copper phthalocyanine on the surfaces of Ge(001)-2 x 1 and Ge(111)-c(2 x 8) is presented. As a first step, intrinsic NEXAFS spectra are established through a combination of the computational technique of DFT and an experiment of a well ordered monolayer film on the weakly interacting highly oriented pyrolytic graphite substrate. This reveals sigma* intensity in the usual pi* region, which is excluded in subsequent analysis of the orientation of molecules. At monolayer coverage the molecules lie close to parallel to the substrate, whereas in a thin film they tend towards perpendicular to the substrate. On the more weakly interacting Ge(111) surface the orientation is more extremal for both monolayer and thin film, indicating possible contributions from both disorder and an adsorption-related extrinsic effect on Ge(001). (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim