Interface-anisotropy induced asymmetry of intermixing in bilayers

The ion-sputtering induced intermixing is studied by molecular dynamics (MD) simulations and by Auger electron spectroscopy depth profiling (AES-DP) analysis in Pt/Ti/Si substrate (Pt/Ti) and Ta/Ti/Pt/Si substrate (Ti/Pt) multilayers. Experimental evidence is found for the asymmetry of intermixing in Pt/Ti and in Ti/Pt. An unexpected enhancement of the injection of the heavy Pt atoms into the Ti substrate is observed both by AES-DP and by MD simulations. In Ti/Pt we get a much weaker interdiffusion than in Pt/Ti. The asymmetry is explained by the backscattering of hyperthermal particles at the mass-anisotropic interface and which is reproduced by computer atomistic simulations. The AES-DP measurements support our earlier predictions (P. S\"ule, M. Menyh\'ard, Phys. Rev., {\bf B71}, 113413 (2005)) obtained for mass-anisotropic bilayers.