SEGREGATION EFFECT ON GRAIN-BOUNDARY DIFFUSION IN THIN METALLIC-FILMS

The diffusion in Au-Cu and Pt-Cu thin films has been studied by Ruther ford backscattering sperctrometry (RES) under the kinetic regimes B (w ithin the temperature interval of 175-290 degrees C) and C (room tempe rature). The 1.5-2.0 MeV He+ RES spectra were taken using 14-18 keV re solution. The RBS spectra were changed to depth-concentration profiles for both bulk and grain boundary (GB) diffusion. Under kinetic regime C the absolute values of GB diffusion coefficients were obtained. Und er kinetic regime B the triple products delta K-b (delta is the GB wid th, D-b is the GB diffusion coefficient, K is the enrichment ratio) we re obtained using the Whipple and Gilmer-Farrell models. The activatio n energies for GB diffusion of Au into Cu films and Cu into Au films a re close to 0.95-0.98 eV atom(-1), whereas the activation energy for G B diffusion of Pt into Cu films is equal to 1.25 eV atom(-1). The comp arison between the data on the GB diffusion for kinetic regime B extra polated to room temperature and the data on the GB diffusion for kinet ic regime C enables one to derive the product delta K and to separate the contribution of segregation to the parameters of GB diffusion for the systems under study.