In-situ investigation of the formation of eutectic alloys in the systems silicon–silver and silicon–copper

Abstract

An in-situ electron microscopic investigation of the formation of eutectic alloys in the systems amorphous Si/particle Ag and amorphous Si/particle Cu showed that the formation of eutectics is preceded by metal diffusion into amorphous silicon with the formation of metastable amorphous metal silicide. Decomposition of the formed metastable amorphous metal silicide results in the evolution of polycrystalline silicon. An oriented formation of liquid eutectic alloy is observed in the systems crystalline (100) Si/particle Ag and (100) Si/particle Cu. In these cases, at the metal–silicon eutectic/silicon crystal interface the formation of silicide phases and a dislocation structure are observed. Investigations allowed us to propose a scheme for the formation of eutectic alloys in the studied systems. The scheme involves the diffusion of metal atoms into the silicon crystal structure, leading to the formation of a metastable silicide or solid solution, the occurrence of strain at the interface and, as a consequence, the formation of defects of different types. The subsequent process is accompanied by synchronous dissolution of metal atoms into the liquid eutectics and by diffusion from the liquid eutectics to the solid crystalline silicon phase, giving rise to metastable silicide, so that an intermediate diffusion zone is always present at the interface between the liquid eutectics and crystalline silicon.