Application of X-ray absorption spectroscopy to the structural characterisation of monodispersed benzotriazole coatings on partly oxidised copper thin films

X-Ray absorption spectroscopy using synchrotron radiation has been used to probe the structure of Copper-benzotriazole complexes and that of the benzotriazole involved in surface films following adsorption onto partly oxidised Cu thin films. Data recorded at the Cu-K edge and, using 4- and 5-bromo-substituted benzotriazole, at the Br-K edge are consistent with the CuI atoms coordinated to three or four benzotriazole molecules through the N(2) position on the triazole ring. Examination of the thin films using glancing-angle geometry suggests the adsorbed film to be only a few monolayers in thickness with the benzotriazole molecules coordinated to CuI ions in the oxidised Cu surface forming a hydrogen-bonded surface complex similar, in part, to that proposed by Fang et al. (Surf. Sci., 1986, 176, 476). At the interface the surface reaction appears to involve a topotactic arrangement with the (100) plane of Cu2O where the in-plane Cu–Cu interatomic distances closely match that expected for the surface complex. The overall limitations of the glancing-angle technique to the characterisation of this kind of interfacial system are discussed.