Determination of molecular orientation in ultrathin films of aminophenylthiolate on Cu (100) prepared by vapour phase deposition

Abstract

Ultrathin layers of aminophenylthiol on Cu(100) were prepared by vapour phase deposition of 4,4'-diaminodiphenyldisulphide (DAPS). Composition and molecular orientation in the films were determined by X-ray photoelectron spectroscopy (XPS) and near edge X-ray absorption fine structure (NEXAFS) spectroscopy. DAPS molecules adsorb on Cu(100) by dissociation of the intramolecular S-S bond and the formation of aminophenylthiolate at the copper surface. NEXAFS spectra indicate the presence of well-ordered monolayers with the plane of the phenyl ring tilted by 24° with respect to the surface normal. The same tilt-angle is found in the submonolayer regime.