On the role of oxygen in the catalysis of C54 titanium disilicide by Ti5Si3 phase

The influence of the native SiO2 in the phase formation sequence of Ti∕Si system has been studied. Furnace annealing of Ti∕Si couples has been investigated by secondary-ion-mass spectrometry, Rutherford backscattering, and glancing incidence x-ray diffraction. The influence of dilute concentration of oxygen at the interface in altering reaction kinetics was studied. These studies reveal that the highly metallic Ti5Si3 phase forms during the intermediate stages of heat treatment. This phase is found to catalyze the direct formation of the low-resistive C54 TiSi2 phase, completely bypassing its polymorphic C49 counterpart. X-ray-diffraction line profile analysis of Bragg peaks indicates that the formation of the C54 phase is accompanied by a reduction in the microstrain. Subsequent annealing results in the complete transformation to TiSi2 with an increase in the average grain size.