Prediction of silicide formation and stability using heats of formation

The effective heat of formation (EHF) model is used to predict compound phase formation and stability in metal-silicon systems. The model defines an effective heat of formation Delta H', which is concentration dependent and shows a linear dependence on the concentration of the limiting element at the growth interface. For instance if CrSi2 (Cr0.33Si0.67) formation is considered and the effective concentration of the interacting atomic species is 20 at.% Cr and 80 at.% Si, then Cr is the limiting species. The effective concentration at an interface is taken to be the composition of the liquidus minimum of the binary system, as the greatest mobility of the atoms at an interface and therefore the most effective mixing, is expected to take place at this composition. It is also shown how the EHF model can be used to predict the phase formation sequence in thin him systems and to explain the influence of impurities and diffusion barriers on compound formation. The anomalous and somewhat contradicting results for initial formation of titanium silicide phases can also be evaluated by using the EHF model.