The Role of Iron in Ti on the Growth of Ti Silicides in Bulk Ti/Si Diffusion Couples

Abstract

Reaction diffusion in the Ti-Si system has been studied to clarify the roll of iron in Ti on the growth of TiSi 2 by using sandwich type diffusion couples consisting of 99.5%(2N)Ti, 99.9999%(6N) Ti and oriented Si wafer in the temperature range between 1164 and 1323 K. The growth of TiSi 2 formed in 2N-Ti/Si diffusion couples at the lowest temperature in this experiment, 1164 K, was slower than that in a 6N-Ti/Si couples. The difference between the growth rate of 2N-Ti/Si and that in 6N-Ti/Si diffusion couples becomes to be small and to have the same value at 1213 K. These results could be expected from our previous experimental results that the higher the purity of Ti the faster the growth rate and that the lower the purity of Ti the larger the activation energy in the temperature range between 973 and 1123 K. However, the Arrhenius plot of the growth rate, k 2 , for 2N-Ti/Si couple bends at 1213 K and have the same value as the 6N-Ti/Si diffusion couples above 1213 K. As a possible explanation for this behavior of the growth of TiSi 2 in the 2N-Ti/Si couple it has been considered that in the high temperature range impurity iron atoms which segregate at grain boundaries of TiSi 2 and slow down the movement of titanium and silicon atoms diffusing through the grain boundaries in the lower temperature range will redistribute into matrix and the effects become negligible small at high temperature.