Transmission Electron Microscopic Studies of TiSi2 Microstructures and the C49-C54 Phase Transformation in Narrow Lines

Transmission electron microscopy was used to study phase transformation of TiSi2 from C49 to C54 phases. By the pre-amorphization implantation (PAI) treatment, the metastable C49 grain size is reduced and shows heavily defective structures. In particular, circular distributed defects surrounding a less-defective region are frequently observed for the C49 matrix. These regions are found to have mosaic structures while maintaining specific orientation. The results indicate two-dimensional growth of C49 from the less-defective region to the circular defective region. Furthermore, heterogeneous nucleation of C54 is often observed at the defective regions. This suggests local stress associated with this two-dimensional growth which enhances the heterogeneous nucleation of C54. On the contrary, strong epitaxial relationships between C49 grains and Si substrate are observed with high concentration in non-PAI samples. Since these C49 grains aligned on the substrate are considered to be stable even at relatively high temperatures, C54 nucleation sites are assumed to markedly decrease in narrow lines.