Ge-Te-Ti Thin Films for High Performance Phase Change Optical Recording

Abstract

It has been known for some time now that thin GeTe films are readily prepared in the amorphous state by a variety of deposition techniques. The films are stable at room temperature but convert to the crystalline state upon thermal treatment. The amorphous-to-crystalline transition occurs at 150° C with significant changes in optical constants.1 The GeTe thin film as a phase change optical recording layer was considered in 19722 but has not been seriously looked at until recently. The recent study3 on the laser-induced phase transformation kinetics reveals that the crystallization rate of GeTe film is slow (250 ns crystallization time) and a deviation in either direction from the stoichiometric composition seriously retards the crystallization kinetics. On the basis of these observations it may be assumed that any of the GeTe phase change media is unable to support the high data transfer rate sought in optical recording.