Phase transition kinetics and recording characteristics of nanocomposite layers prepared by sputtering process utilizing AgInSbTe-SiO2 composite target

Abstract

AgInSbTe (AIST)-SiO2 nanocomposite thin films were successfully prepared by sputtering deposition utilizing an AIST-SiO2 composite target and their phase-transition behaviors were investigated. Transmission electron microscopy (TEM) revealed that the as-deposited composite layer contained nano-scale quaternary alloy particles about 5 nm in size randomly embedded in the SiO2 matrix. In situ reflectivity-temperature measurements showed that the AIST-SiO2 nanocomposite and pristine AIST layers exhibit similar abrupt reflectivity changes at about 200 degrees C. However, the presence of the SiO2 phase hindered particle growth in the nanocomposite layers which, in turn, caused a mild increase in the phase-transition temperatures. Johnson-Mehl-Avrami (JMA) analysis indicated that, regardless of the film thickness, the amorphous-to-crystalline transition in nanocomposite layers proceeds in a bulk-like manner. Dynamic tests revealed that modulations higher than 0.8, 0.6, and 0.5 were achieved when 11T, 4T, and 3T signals, respectively were. written in the one-layer AIST-SiO2 disk sample. The unique phase transition behavior of nanocomposite layers and signal property analysis of disk samples demonstrated that a nanocomposite layer can be a new alternative for write-once optical data storage.