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 paper. The layer, the 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 interdiffusion of Au and Sn. Deposition at high temperature forms more Au rich compositions compared to postannealing at the same temperature due to the kinetic energy of the impinging Sn atoms in the former case. Postannealing, on the other hand, stabilizes the bulk phases such as AuSn and Au5Sn and exhibits an activated behavior for transition from the former to the latter with increasing temperature. The XPS valence-band spectra of AuSn and Au5Sn layers show good agreement with the density functional theory calculation, indicating that these have the bulk structure reported in literature. However, the influence of antisite defects is observed in Au5Sn. Low-energy electron-diffraction study reveals that although the AuSn layer is ordered its top surface is disordered at room temperature. Surface order is obtained by annealing or deposition at elevated temperatures and dispersing bands are observed by angle-resolved photoemission spectroscopy. Both electronlike and holelike bands are evident for the (root 3 x root 3)R30 degrees phase, while a nearly free electronlike parabolic surface state is observed for the p(3 x 3)R15 degrees phase.