GRAIN-BOUNDARY DIFFUSION EFFECTS ON THE SPUTTER DEPTH PROFILES OF CO-AG BILAYERS

We investigated the effects of surface roughness and grain boundary di ffusion (GBD) at elevated temperatures on the Auger-electron-spectrosc opy sputter depth profiles of Co-Ag bilayers and the GBD process of Ag , atoms in Co. The Ag layer in the Ag/Co bilayer is transformed from a uniform layer to discrete islands by heat treatment. Enhanced mobilit y during sputtering at elevated temperatures makes Ag atoms migrate co ntinually from islands to cover neighboring exposed Co, which reduces the size of Ag islands. On the other hand, the surface morphological m odification of Co/Ag bilayer does not occur by heat treatment, and the depth profile at 340 degrees C resembles that from a uniformly interm ixed film, which shows a drastic difference from that of Ag/Co. This i s explained with a very thin and stable accumulation of Ag on the Co l ayer by GBD, A model of structural changes in Co/Ag subjected to ion s puttering at elevated temperatures is proposed on the basis of the res ults. The activation energy and pre-exponential factor for GBD of Ag i n Co are found to be 0.46+/-0.06 eV and similar to 1x10(-8) cm(2)/s, r espectively. (C) 1996 American Institute of Physics.