Crucial role of residual gases in amorphization of crystalline films

Abstract

A series of recent studies has claimed the amorphization of a crystalline multilayer film by a solid-state reaction during a vacuum anneal. The present study on Ni-Zr alloys establishes in two ways that the residual gases present in a vacuum system [(4–6×${10}^{\mathrm{-}7}$ Torr] play an important role in the amorphization process. First, the superconducting transition temperature (which is sensitive to such residual gases) of as-deposited amorphous Ni-Zr films decreases and eventually vanishes during annealing treatments similar to those used in the amorphization of multilayers. The amorphized multilayers are superconducting at much lower temperatures than amorphous films of similar compositions. Second, annealing the multilayers in such a way as to avoid the effect of residual gases (in situ annealing in a protective getter-sputtering atmosphere) does not lead to amorphization.