Suitability of Ge-As-Te system for optical data storage

Abstract

We report the study of crystallization kinetics and time-temperature-transformation in alloys of Ge7.5AsxTe92.5-x (x=20, 40, 45, 47.5, 50, 52.5, 55) and Ge10AsxTe90-x (x=15, 20, 22.5, 35, 40, 45, 50), in order to examine the suitability of these alloys for reversible phase change optical recording (RPCOR) films, which is one of the leading optical storage devices. Using the values of viscosity and kinetics of crystal nucleation and growth process, the time-temperature-transformation curves were obtained. The variation of critical parameters such as minimum erasure time and thermal stability has been calculated as a function of composition. It has been observed that for our samples, the critical cooling rate is high (2.1*105-4.3*104 K/min) for Ge10AsxTe90-x (x=15, 20, 22.5, 35, 40, 45, 50) and 1.51*105-2.91*104 K/min for Ge7.5AsxTe92.5-x (x=15, 20, 22.5, 35, 40, 45, 50) ensuring fast erasure speed ( approximately=1 mu s) which is an essential requirement for high quality RPCOR films. It is suggested that the material with lower concentration of Germanium (<10 at.%), Arsenide and Tellurium concentration between (35-55 at.%) are better contenders for the above application.