Improvement in thermal stability and crystallization mechanism of Sm doped Ge2Sb2Te5 thin films for phase change memory applications

The thin films of (Ge2Sb2Te5)(100-x)Sm-x (x = 0, 0.2, 0.4, 0.6, 0.8, 1.0, 1.2) (Sm-GST) phase change material have been investigated employing X-ray photoelectron spectroscopy (XPS) to examine the nature of chemical bonding in as-deposited thin films of Sm-GST. The composition of as-deposited thin films of Sm-GST has been also analyzed from the peak area ratios of XPS core-level spectra and the morphology of the thin film has been studied using field emission scanning electron microscopy (FESEM). The powder samples obtained from the as-deposited thin films have been utilized for the non-isothermal differential scanning calorimetry (DSC) measurements at the constant heating rate of 10 K/min. The values of glass transition temperature (T-g), onset crystallization (T-c), peak crystallization temperature (T-p) and melting temperature (T-m) obtained from DSC curves of Sm-GST thin films have been used for the evaluation of thermal stability parameters. The activation energy for crystallization (E-c) and avrami exponent (n) for fcc and hexagonal phase of Sm-GST thin films have been evaluated using Henderson's method and Matusita's method. The impact of Sm doping on the thermal stability, glass-forming ability and crystallization activation energy of as-deposited thin films have been examined and its possible influence on the memory device performance has been correlated. (C) 2021 Elsevier B.V. All rights reserved.