Bi-layers which had been deposited onto SiO2/Si substrates were bombarded with 300 to 750keV Ar and Xe ions, at 20, 77 or 300K, in order to study beam-induced mixing in the normally immiscible system. Rutherford back-scattering spectroscopy channelling, conversion electron Mössbauer spectroscopy and scanning tunnelling microscopy were used to analyze atomic transport at the interface, and the resultant morphological changes. On the basis of the small amount of Ag that was dissolved in Fe, and the sharpness of elemental profiles at the interface, a mixing efficiency was deduced which was appreciably smaller than that predicted by the ballistic model. Because ballistic mixing was expected to occur, it was argued that de-mixing and phase separation occurred in the relaxation stage or thermal spike phase of the collision cascade; due to the positive heat of mixing.

A.Crespo-Sosa, P.Schaaf, W.Bolse, K.P.Lieb, M.Gimbel, U.Geyer, C.Tosello: Physical Review B, 1996, 53[22], 14795-805