DETERMINATION OF MOLECULAR-ORIENTATION IN ULTRATHIN FILMS OF AMINOPHENYLTHIOLATE ON CU(100) PREPARED BY VAPOR-PHASE DEPOSITION

Ultrathin layers of aminophenylthiol on Cu (100) were prepared by vapour phase deposition of 4,4'-diamino-diphenyldisulphide (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-degrees with respect to the surface normal. The same tilt-angle is found in the submonolayer regime.