Nucleation and growth of C54 grains into C49TiSi(2) thin films monitored by micro-Raman imaging

The first-order C49-C54 allotropic-phase transition has been studied in TiS i2 thin films by electrical measurements and micro-Raman spectroscopy. To e valuate the parameters describing the kinetics of the transition and the ba rrier energy for the nucleation, micro-Raman spectroscopy has been used as a microscopy technique: spectra have been acquired scanning large silicide areas (100x50 mum(2)) and have been processed to obtain images which show t he morphological evolution of the C54 grains during the transition. For tem peratures between 680 and 720 degreesC, the converted area fraction has bee n determined at different annealing times and compared with electrical meas urements. The two methods agree quite well. Both density and size of the C5 4 grains have been measured, thus allowing to separately determine the nucl eation 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 velocit y. Such values, coincident within experimental errors, indicate that the nu cleation barrier energy for the transition to the C54 phase is very low. (C ) 2000 American Institute of Physics. [S0021-8979(01)03101-2].