Electron energy loss spectroscopy study of the effect of low-energy Ar+-ion bombardment on the surface structure and composition of Pt80Co20 (1Â 1Â 1) alloy

Electron energy loss spectroscopy has been employed for investigation of the effect of 600 eV Ar+-ion irradiation in the dose range 7×1016-4×1017 ions/cm2 on the atomic structure and surface composition of alloy Pt80Co20(1 1 1). A method of the layer-by-layer reconstruction of the lattice interplanar distance changes based on the analysis of the plasmon spectra excitation was proposed. The ion bombardment was shown to result in a non-monotonic variation of the lattice interplanar distance due to formation of the stable defects, with the topmost layer being in the state of compression. Using the ionization energy loss spectra, a layer-by-layer concentration profile of the alloy components was reconstructed for different doses of ion irradiation of the surface. The Ar+-ion bombardment of the alloy was found to result in the preferential sputtering of Co and in the enrichment of the near-surface region by Pt atoms with formation of an altered layer, which is characterized by a non-monotonic concentration profile dependent on the irradiation dose. The results obtained are discussed in the framework of the models of preferential sputtering and radiation-induced segregation.