We discuss the rather scattered measurements of the lattice parameters for C49 TiSi2, which are reported in literature, along with new and accurate X-ray diffraction measurements and ab-initio calculations. Both agree in indicating that the density of the metastable C49 structure cannot be much smaller than the one for the polymorphic C54 phase, as it is commonly reported. We conclude by demonstrating that only in the case of such a smaller difference in density between the two phases, the elastic strain contribution to the nucleation energy of the C54 structure in the C49 matrix can be neglected. The estimation of the critical radius strongly depends on this issue.

A series of fine grained C49 thin films were prepared by depositing Ti films on heated amorphous as well as crystalline silicon substrates.

Rapid thermal processing at temperatures between 700 and 775 °C was used to transform the metastable C49 phase into the stable C54. The evolution of the film structure and morphology during the transformation was investigated by sheet resistance, optical spectroscopy, diffuse reflectance and AFM measurements. One structural model which could account for our data is proposed according to crystallographic information present in the literature.