Growth morphology, composition and thermal behaviour of ultra-thin GeSx films deposited on Ni under UHV conditions have been studied by X-ray photoelectron spectroscopy and X-ray Auger electron spectroscopy. The flux emitted by the GeSx evaporation source consisted of GeS and S-2 molecules which condensed on the substrate to yield a film in which the first layer was S-rich, subsequent layers growing with a composition close to GeS2. The Ge and S Auger spectra and the Ge 3d X-ray photoelectron spectra clearly discriminate between the contact layer and subsequent layers. Ge Auger parameters indicate that Ge atoms in the first layer are in contact with metallic Ni and are consistent with GeS2 formation in the higher layers. The growth mode and agglomeration behaviour of the evaporated film are described and discussed.