The electronic structure of Au-Sn intermetallic layers of different compositions grown on Au (111) to the thickness of several nanometers has been studied in this work. The layer, interface and the substrate related components in the Au 4f and Sn 4d core-level spectra obtained using x-ray photoelectron spectroscopy (XPS) vary with deposition parameters to reveal the details of the Au-Sn formation. While AuSn is grown by deposition at room temperature, Au rich compounds form as a result of heat treatment through inter diffusion of Au and Sn. Deposition at high temperature arXiv:1911.10002v2 [cond-mat.mtrl-sci]