The irradiation-induced silicide formation in ion beam-mixed layer of Au/Si(1 0 0) system was investigated by using 200 keV Kr+ and 350 keV Xe+ ions to fluences ranging from 8×1014 to 1×1016 ions/cm2 at room temperature. The thickness of Au layer evaporated on Si substrate was ∼500 Å. Rutherford backscattering spectrometry (RBS) experiments were carried out to study the irradiation effects on the mixed layers. We observed that at the fluence of 1×1016 Kr+/cm2 and starting from the fluence of 8×1014 Xe+/cm2, a total mixing of the deposited Au layer with Si was obtained. RBS data corresponding to the fluences of 1×1016 Kr+/cm2 and 8×1014 Xe+/cm2 clearly showed mixed layers with homogenous concentrations of Au and Si atoms which can be attributed to gold silicides. The samples irradiated to fluences of 1×1016 Kr+/cm2 and 1×1016 Xe+/cm2 were also analyzed by X-ray photoelectron spectroscopy (XPS). The observed chemical shift of Au 4f and Si 2p lines confirmed the formation of gold silicides at the surface of the mixed layers. Au2Si phase is obtained with Kr+ irradiation whereas the formed phase with Xe+ ions is more enriched in Si atoms. © 2006 Elsevier Ltd. All rights reserved