Nucleation and growth of C54 grains into C49 TiSi[sub 2] thin films monitored by micro-Raman imaging

The first-order C49-C54 allotropic-phase transition has been studied in TiSi2 thin films by electrical measurements and micro-Raman spectroscopy. To evaluate the parameters describing the kinetics of the transition and the barrier energy for the nucleation, micro-Raman spectroscopy has been used as a microscopy technique: spectra have been acquired scanning large silicide areas (100 × 50 μm2) and have been processed to obtain images which show the morphological evolution of the C54 grains during the transition. For temperatures between 680 and 720°C, the converted area fraction has been determined at different annealing times and compared with electrical measurements. The two methods agree quite well. Both density and size of the C54 grains have been measured, thus allowing to separately determine the nucleation and growth parameters as a function of temperature. A nucleation and growth model has been fitted to data obtaining an activation energy of 4.9±0.7 eV for the nucleation rate and 4.5±0.9 eV for the growth velocity. Such values, coincident within experimental errors, indicate that the nucleation barrier energy for the transition to the C54 phase is very low. © 2000 American Institute of Physics.