Effect of local structure on the optical and dielectric behaviour of Sm doped GeSbTe phase change material

Abstract

Abstract Ge2Sb2Te5 (GST) is considered to be one of the most prominent phase change materials for data storage applications. The UV–Vis–NIR transmittance spectra of (Ge2Sb2Te5)100-xSmx (x = 0, 0.2, 0.4, 0.6, 0.8, 1.0, 1.2) thin films are utilized to analyze the effect of rare earth element Sm on the optical behaviour of GST. The linear and nonlinear optical studies of GST on Sm incorporation provide the understanding of electron transport properties and band structural details. The optical parameters such as absorption coefficient (α) and the refractive index are obtained through transmission data and are analyzed for Sm doped GST thin films. There is significant change of the absorption coefficient near the optical band gap for (Ge2Sb2Te5)100-xSmx thin films. The optical dispersion parameters are analyzed to understand the material's structure. The optical band gap, Urbach energy, and disorder of Sm doped GST thin films are analyzed for band structure modification details on Sm addition. The free career concentration to electron effective mass ratio and high-frequency dielectric constant for (Ge2Sb2Te5)100-xSmx thin films are analyzed. Optical conductivity, dielectric constant, surface and bulk energy loss function and tan δ loss function for (Ge2Sb2Te5)100-xSmx thin films are obtained. The optical non-linear parameters are analyzed to understand the dependence of the polarizability of GST on Sm addition. The incorporation of Sm leads to the change in local bonding environment which may improve the switching mechanism of phase change memory devices.