Phase transformations induced by rapid thermal annealing in Ti-Si and W-Si alloys

The crystallization of amorphous TiSi2 coevaporated and WSi2.4 chemical vapor deposited thin films was performed by tungsten lamp annealing system at various temperatures and time. A typical annealing process was composed of a fast heating at a constant rate of ~83 °C/ s up to the required temperature, followed by a fast cooling step to room temperature. A metastable form of TiSi2 (base-centered orthorhombic) and of WSi2 (hexagonal) is formed first and the entire amorphous layer is consumed before this phase undergoes a polymorphic transformation to face-centered-orthorhombic TiSi2 and to tetragonal WSi2, respectively, at higher temperatures. The temperature of transformations are found well correlated with those measured in furnace annealing processes, with typical heating rates varying from 1 to 50 °C/min, and reported in an Ozawa's plot (logarithm of the heating rate versus reciprocal of the temperature of transformation) to evaluate the activation energies of the aforesaid transformations. These latter ones were investigated in this work using room-temperature sheet resistance measurements and the x-ray diffraction technique. In the face-centered-orthorhombic TiSi2 and tetragonal WSi2 phases, when fully annealed, the resistivities are 14 and 56 ?? cm at room temperature, respectively.