Effect of a substrate on the phase transformations of amorphous TiSi ₂ thin films

Abstract

The crystallization of an amorphous TiSi2 evaporated film has been studied on both poly-Si and SiO2 substrates. A metastable form of TiSi2 (base-centered orthorhombic; a=3.62 A, b=13.76 A, and c=3.605 A) [P. G. Cotter, J. H. Kohn, and R. A. Potter, J. Am. Ceram. Soc. 39, 11 (1956)] is formed first at a temperature of approximately 350°C on both substrates. This phase consumes the entire amorphous layer before undergoing a polymorphic transformation to face-centered orthorhombic TiSi2 (a=8.24 A, b=4.78 A, and c=8.54 A) [F. Laves and H. J. Wallbaum, Z. Kristallogr. 101, 78 (1979)] at 600 and 800°C on poly-Si and SiO2, respectively. These transformations were investigated using in situ resistivity, x-ray diffraction, and transmission electron microscopy. The room-temperature resistivities observed were 96 and 20 μΩ cm for the base-centered and face-centered TiSi2, respectively. The enhanced polymorphic transformation on poly-Si over SiO2 is explained by a lowering of surface energy barrier to nucleation.