Reactive diffusion in bulk Co/Si diffusion couple

Reactive diffusion of the Go-Si binary system has been studied by using bul k diffusion couples consisting of a 99.98% and 99.997%Co plate and a [100] oriented Si wafer in the temperature range from 973 K to 1273 K. The experi mental results were compared with the previous results obtained by using Co thin film/bulk Si and bulk Co/bulk Si diffusion couples. In these bulk dif fusion couples, 3 kinds of Co silicides (Co2Si, CoSi, CoSi2) were formed. A U of them grew according to the parabolic law. The interdiffusion coefficie nts of CoSi in the bulk diffusion couples almost coincide with the values f or thin film diffusion couples. However, the values of interdiffusion coeff icients of Co2Si for the bulk diffusion couples and thin film diffusion cou ples do not agree with each other. If the first crystalline phase is Co2Si in Co/Si diffusion couples, the reason for the difference in interdiffusion coefficients between the thin film and bulk samples can be explained by th e fast diffusion such as grain boundary diffusion in the thin film diffusio n couples.