Enhancing the surface morphology for improved phase change mechanism by Sm doping in Ge2Sb2Te5 thin films

Abstract

The effect of doping of rare earth element Sm to Ge2Sb2Te5 (GST) phase change material (PCM) on the surface morphology in (Ge2Sb2Te5)100−xSmx (x = 0, 0.6, 1.2) thin films is investigated employing atomic force microscopy (AFM). The incorporation of Sm to GST thin films indicates composition dependent grain size distribution and surface roughness. The Sm doping impacts the nucleation dominated crystallization mechanism of GST phase change material. The root mean square roughness value in AFM micrographs of the thin films decreases with Sm content. The RMS roughness (Rq) to average roughness (Ra) ratio value 1.119 for x = 0.6% of Sm-doped GST thin films, points to the Gaussian distribution of grain sizes. The average grain size of (Ge2Sb2Te5)100−xSmx (x = 0, 0.6, 1.2) thin films shows a decrease on Sm incorporation which may be attributed to the compositional dependence of crystallization activation energy for phase change. Few sharp spikes on the thin film for x = 1.2 of Sm addition to GST suggest an increase in the hexagonal phase as compared to the fcc phase which may alter the mechanism of phase transition in these PCMs.