Structural Optical and Thermal Studies of Rare Earth Sm Doped Ge2Sb2Te5 Phase Change Material

Abstract

The advancements in memory devices for achieving efficient computing performance is one of the recent areas in research and development. Phase change (PC) memories are among the leading next generation memory technology. The basic principle behind the working of PC memories is based upon the repeated reversible phase transformation of chalcogenide PC materials which are induced thermally. The unique features of Ge2Sb2Te5 (GST) such as higher crystallization temperature (~160and#8304;C), faster switching speed (~60ns) and better contrast in the amorphous and crystalline phases for electrical resistivity and optical reflectivity makes it a novel material for such purpose. The GST exhibits the amorphous, rocksalt cubic (fcc) and hexagonal crystal structure at different temperatures. The addition of impurity element to GST is an effective method for the improvement of switching performance by inducing the change in chemical bonding nature and local structural network which alters the optical, electrical and thermal characteristics. In the current work the outcome of Sm doping on the local structure, optical behavior, crystallization kinetics and electrical properties has been studied. newlineThe bulk alloys of (Ge2Sb2Te5)100-xSmx PC material have been prepared by means of the melt-quenching process. The thin film deposition for Sm added GST samples have been carried out by employing thermal evaporation. The crystal structure of powder material of (Ge2Sb2Te5)100-xSmx bulk alloys has been studied by employing the X-ray diffraction (XRD) analysis and rietveld refinement by Fullprof software for phase quantification thereafter. The local structures of these samples have been probed employing the Raman spectroscopy analysis using 785 nm laser excitation and the FTIR measurements in 30 cm-1 to 300 cm-1 range. The XRD analysis of (Ge2Sb2Te5)100-xSmx thin films show amorphous nature. The elemental analysis of the thin films has been done using the FESEM mapping newline