Irradiation-induced silicide formation in the ion beam-mixed Au/Si(1Â 0Â 0) system at room temperature

The irradiation-induced silicide formation in an ion-beam-mixed layer of Au/Si(1 0 0) system was investigated by using 120 keV Ar+ ions to the fluences of 1×1016 and 3×1016 ions/cm2 at room temperature. The thickness of Au layer evaporated on Si substrate was ∼500 Å. RBS experiments were carried out to study the irradiation effects on the mixed layer. We note that at a fluence of 1×1016 ions/cm2, total mixing of the Au layer with Si is obtained. A computer program is developed to extract the depth profiles of Au and Si atoms for each fluence. The depth profiles obtained for the fluence of 1×1016 ions/cm2 reveal two distinct regions. At the surface, we observe a mixed layer with homogenous concentrations of Au and Si atoms which is of the approximate composition of Au70Si30. For the fluence of 3×1016 ions/cm2, the depth profiles of Au and Si atoms are similar except that the thickness of the interface between the Au70Si30 layer and Si substrate is reduced. The sample irradiated to the fluence of 3×1016 ions/cm2 was analyzed by X-ray photoelectron spectroscopy. The chemical shift of both Au 4f7/2 and Si 2p lines was measured. The XPS depth profiles of Au and Si atoms and the observed chemical shift of Au 4f and Si 2p lines confirmed the formation of gold silicide phases at the surface of the ion beam-mixed layer.