Interface stability of Ti(SiG and SiGe alloys: Tie lines in the ternary equilibrium diagram

Abstract

The C54 phases of (Formula presented) and (Formula presented) are known to be completely miscible, however, we have observed that thin films of C54 Ti((Formula presented)(Formula presented)(Formula presented) are not stable in contact with (Formula presented)(Formula presented) when y=x. In this study it is shown that this interface instability can be related to the composition-dependent energetics that determine the Ti-Si-Ge ternary equilibrium diagram. Tie lines of the Ti((Formula presented)(Formula presented)(Formula presented) to (Formula presented)(Formula presented) system were calculated on the basis of classical thermodynamics. The calculations indicate that for C54 Ti((Formula presented)(Formula presented)(Formula presented) to be stable in contact with (Formula presented)(Formula presented)the compositions of the two phases must be such that y<x. The specific compositions of the two phases in equilibrium depend on the temperature and the relative quantities of the two phases. The dynamics of the interface reactions of C54 Ti((Formula presented)(Formula presented)(Formula presented) on (Formula presented)(Formula presented) are related to the calculated tie lines, and the diffusion kinetics of the materials. Experimental results are presented that quantitatively support the model calculations. © 1996 The American Physical Society.