Formation of a C49 TiGe₂ phase during annealing a coevaporated Ti_0.33Ge_0.67 alloy

Abstract

The coevaporated, amorphous Ti0.33Ge0.67 alloy crystallizes at 315°C into a metastable C49 structure, which transforms to the equilibrium C54 structure at higher temperatures around 535°C. This result differs from that obtained from binary reactions between Ti and Ge where the C49 phase is not observed. The electron diffraction pattern for the C49 phase exhibits extra spots as predicted by Bourret et al. for a large period polytype [A. Bourret, F. M. d'Heurle, F. K. LeGoues, and A. Charai, J. Appl. Phys. 67, 241 (1990)]. Additional evidence for the formation of the C49 TiGe2 is found by annealing a Ti0.33Ge0.67/ Ti0.33Si0.67 bilayer. The bilayer crystallizes into a solid solution of C49 TiGe2-TiSi2 before transforming to a C54 solid solution at lower temperatures than pure C49 TiSi2.