Studies of phase formation and chemical states of the ion beam mixed Ag/Si(1 1 1) system

Abstract

Ion beam mixing has been extensively used in metal/metal and metal/silicon systems to promote new phase formations. In the present study a 500 Å thick Ag film was deposited by thermal evaporation on 5% HF-etched Si(1 1 1) at a chamber pressure of 8×10 −6 mbar. The films were irradiated with 100 keV Ar + ions at different temperatures to a dose of 1×10 16 cm −2. Rutherford backscattering spectrometry (RBS) was carried out to observe the mixing of the ion beam irradiated Ag/Si(1 1 1) system. The Ag/Si(1 1 1) system was found to exhibit very low miscibility even at high temperatures of irradiation. The calculated heat of mixing, using Miedema’s method, is less in the Ag–Si system than in to the Au–Si and Cu–Si systems. Consequently, the observed mixing in Ag/Si system is less compared to the Au/Si and Cu/Si systems, which showed strong mixing and phase formation. Reduction of the thickness of the Ag film was observed with the increasing of the temperature of irradiation. Grazing incidence X-ray diffraction (GIXRD) measurements show the formation of Ag 3Si and Ag 2Si for irradiation at 400°C. No significant broadening of the full width at half maxima (FWHM) or binding energy shift of Ag 3d line was observed using X-ray photoelectron spectroscopy (XPS) in the sample ion beam mixed at 400°C compared to the as-deposited sample. A significant broadening of FWHM of the Ag 4s and Si 2p lines, was observed in the sample ion beam mixed at 400°C. The broadening of FWHM in the Ag 4s and Si 2p indicates compound formation.