The role of iron in Ti on the growth of Ti silicides in bulk Ti/Si diffusion couples

Reaction diffusion in the Ti-Si system has been studied to clarify the roll of iron in Ti on the growth of TiSi2 by using sandwich type diffusion coup les consisting of 99.5%(2N)Ti, 99.9999%(6N) Ti and [111] oriented Si wafer in the temperature range between 1164 and 1323 K. The growth of TiSi2 forme d in 2N-Ti/Si diffusion couples at the lowest temperature in this experimen t, 1164 K, was slower than that in a 6N-Ti/Si couples. The difference betwe en the growth rate of 2N-Ti/Si and that in 6N-Ti/Si diffusion couples becom es 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 l arger 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 TiSi2 in the 2 N-Ti/Si couple it has been considered that in the high temperature range im purity iron atoms which segregate at grain boundaries of TiSi2 and slow dow n the movement of titanium and silicon atoms diffusing through the grain bo undaries in the lower temperature range will redistribute into matrix and t he effects become negligible small at high temperature.