Thermodynamic investigations of solid-state Si-metal interactions. II. General analysis of Si-metal binary systems

Silicides, amorphous alloys, and metal-induced crystallization of amorphous Si are commonly encountered in solid-state reactions between Si and metals. In order to investigate the possible correlations between these phenomena, a thermodynamic analysis was made on various binary systems consisting of Si and metals. It was revealed that (1) the capability of forming silicides between Si and a transition metal results from the largely negative heat of mixing in a certain medium composition range of the two elements; (2) amorphous Si-metal alloys may form not only in the systems which form silicides, but also in some systems which do not form stable silicides; and (3) the phenomenon of metal-induced crystallization of amorphous Si occurs in a Si-rich composition range of a binary system, which is attributed to the lowering of Si—Si bonding energy, owing to the incorporation of metal species. A model describing the phenomenon is developed.