M-S (M=Mo, W) cluster compound films on copper surfaces

M-S cluster compound films on copper surfaces were investigated by XPS, AES and FT-IR. The results show that MoSCu and WSCu bonds had been formed by the reaction of MoS42− and WS42−, respectively, with the Cu2O layer on a copper surface. The films are composed of the elements Mo(W), S, Cu and O. The valence of each element is +6, −2, +1 and −2, respectively. According to the AES depth profile curves, the relative atomic contents of the elements were estimated and a multimolecular layer structure of the films was verified. Some of the sulfur atoms had been oxidized in the outer molecular layers while MoS4 or WS2 units remain in the inner molecular layers. The thickness of the film was found to depend on the reaction time: longer times resulted in thicker films. The colors of the films are probably caused by a statistical distribution of various layers since the films are complicated multicomponent and multilayer systems.