Thermally processed phase change behavior on the stoichiometric efficacy of quaternary Se77.5-X Te20 Sn2.5 AgX (X=2.5, 5, 7.5) thin films

Abstract

Thin films of the quaternary metal chalcogenide have recently gained attention due to their improved electrical, optical, thermal, and structural properties. The structural, thermal, morphological, optical, and electrical properties of Ag-modified novel quaternary Se-Te-Sn-Ag thin film systems are investigated in this paper. Temperature-dependent structural, electrical, and thermoelectric properties are given special attention. From Differential Thermal Analysis/Thermogravimetric Analysis (DTA/TGA), the Ag content in this composition in-duces thermal stability and crystalline phase as well as glass phase transitions. High-temperature X-ray diffraction (HTXRD) patterns were used to investigate the temperature-dependent structural phase transition, grain size, lattice strain, and dislocation density. The morphological observations show that Ag concentration promotes the nucleation and growth processes of nanorod structures in as-deposited thin films. Optical char-acteristics reveal higher IR transparency in thin films and high refractive indexes in the range of 3.22-3.29. The as-deposited thin films resistivity decreases with increasing temperature and silver content. The Hall measure-ment corroborates the results obtained from the Seebeck measurements, indicating that the samples are n-type. The phase change switching mechanism of phase change devices is still unclear; there are two possible mech-anisms: thermal and electronic models. This work proposes thermally processed phase transition behaviors in structural and electrical studies. The result of the above analyses shows that the quaternary Se-Te-Sn-Ag thin film will be a potential candidate for phase change device applications.