XPS studies of MoS2 formation from ammonium tetrathiomolybdate solutions

Preparation of MoS2 by acidification of ammonium tetrathiomolybdate solution has been studied by X-ray photoelectron spectroscopy (XPS). The precipitates formed from the solution are mainly composed of MoS3, the Mo 3d chemical shift of which is approximately 4.2eV. Heat treatments of the above product at 450 and 850°C, in a vacuum of 1.33 × 10−4 Pa, lead largely to formation of MoS2, with typical chemical shifts of abouth 1.2eV. The MoS2 formed consists of nano-sized, crystalline particles of hexagonal (2H-type) structure. The validity of MoS2 formation by this route is confirmed by comparative study, namely the decomposition of ATT solids under the same respective heat treatment conditions. Apart from these main aspects, origins of minor XPS peaks are also considered.