Studies of phase formation and chemical states of the ion beam mixed Ag/Si(111) system

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 Angstro m thick Ag film was deposited by thermal evaporation on 5% HF-etched Si(1 1 1) at a chamber pressure of 8 x 10(-6) mbar, The films were irradiated wit h 100 keV Ar+ ions at different temperatures to a dose of 1 x 10(16) cm(-2) . Rutherford backscattering spectrometry (RBS) was carried out to observe t he 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 l ess in the Ag-Si system than in to the Au-Si and Cu-Si systems. Consequentl y, 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 t he thickness of the Ag film was observed with the increasing of the tempera ture of irradiation. Grazing incidence X-ray diffraction (GIXRD) measuremen ts show the formation of Ag3Si and Ag2Si for irradiation at 400 degrees C. No significant broadening of the full width at half maxima (FWHM) or bindin g energy shift of Ag 3d line was observed using X-ray photoelectron spectro scopy (XPS) in the sample ion beam mixed at 400 degrees C compared to the a s-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 degrees C. The bro adening of FWHM in the Ag 4s and Si 2p indicates compound formation. (C) 20 00 Elsevier Science B.V. All rights reserved.