Film preparation and structure analysis of optical recording domains of amorphous Ge-Sb-Te

Abstract

A procedure for synthesizing Ge-Sb-Te ternary chalcogenide amorphous films used for phase change erasable optical storage is introduced. In this procedure, a two-target co-sputtering method and several other methods such as sample rotation and target cover were adopted. The optical recording properties of some phase-change erasable films in the Ge-Sb-Te system prepared by this procedure are reported. Some of them show very good optical recording properties such as high-speed erasable optical storage and strong stability at room temperature. The structure of the optical recording domain of the Ge45Sb10Te45 film was also studied by transmission electron microscopy (TEM). It was found that the written domain of Ge45SB10Te45 film is composed of a phase-separated amorphous center region and a crystallized ring-like region around it. The crystals in the ring-like region are identified as tetragonal Ge and hexagonal Te. The erased domain of the same film after a cycle of write/erase operation is composed of a crystallized inner part where the fine GeTe crystal is dominant and a crystallized outer part formed by larger Sb2Te3 crystals.