Enhanced Crystallization Behaviors of Silicon-Doped Sb2Te Films: Optical Evidences.

Shuang Guo,Zhitang Song,Junhao Chu,Liangcai Wu,Tao Li,Zhigao Hu,Liping Xu,Jinzhong Zhang

doi:10.1038/srep33639

Abstract

The optical properties and structural variations of silicon (Si) doped Sb2Te (SST) films as functions of temperature (210–620 K) and Si concentration (0–33%) have been investigated by the means of temperature dependent Raman scattering and spectroscopic ellipsometry experiments. Based upon the changes in Raman phonon modes and dielectric functions, it can be concluded that the temperature ranges for intermediates and transition states are estimated to 150, 120, 90, and 0 K, corresponding to ST, SST25%, SST28%, and SST33% films, respectively. The phenomenon also can be summarized by the thermal evolutions of interband electronic transition energies (En) and partial spectral weight integral (I). The disappearance of intermediate (INT) state for SST33% film between amorphous (AM) and hexagonal (HEX) phases can be attributed to the acceleratory crystallization of HEX phase by Si introduction. It illustrates that the risk of phase separation (Sb and Te) during the cyclic phase-change processes decreases with the increasing Si concentration. The enhanced crystallization behaviors can optimize the data retention ability and the long term stability of ST by Si doping, which are important indicators for phase change materials. The performance improvement has been analyzed qualitatively from the optical perspective.

Highlights

The optical properties and structural variations of silicon (Si) doped Sb2Te (SST) films as functions of temperature (210–620 K) and Si concentration (0–33%) have been investigated by the means of temperature dependent Raman scattering and spectroscopic ellipsometry experiments
The crystallization temperature (AM-INT/HEX) is elevated from 410 to 440 K with the Si concentration increasing to 33%
It illustrates that the possibility of phase separation (Sb and Te) during the cyclic phase-change processes decreases with the increasing Si concentration

Summary

Introduction

The optical properties and structural variations of silicon (Si) doped Sb2Te (SST) films as functions of temperature (210–620 K) and Si concentration (0–33%) have been investigated by the means of temperature dependent Raman scattering and spectroscopic ellipsometry experiments. The disappearance of intermediate (INT) state for SST33% film between amorphous (AM) and hexagonal (HEX) phases can be attributed to the acceleratory crystallization of HEX phase by Si introduction It illustrates that the risk of phase separation (Sb and Te) during the cyclic phase-change processes decreases with the increasing Si concentration. Among the Si-doped Sb-Te material systems, Si doped Sb2Te (SST) has been confirmed with a higher crystallization temperature and a superior thermal stability of the amorphous phase, as well as a better data retention ability by the means of electrical and thermal characterization methods[23,24]. The lattice dynamics, optical constants, and electronic transitions of SST films as functions of temperature and Si concentration have been discussed in detail

Methods

Results

Conclusion