The impact of vacancies on the stability of cubic phases in Sb–Te binary compounds

• Published in: NPG Asia materials 2019-07, Vol.11 (1), p.1-8, Article 40
• Main Authors: Chen, Xin, Liu, Xianqiang, Cheng, Yan, Song, Zhitang
• Format: Article
• Language: English
• Subjects: 639/301/1034; 639/301/119/2795; 639/766/1130; Antimony; Binary systems; Biomaterials; Charge density; Chemistry and Materials Science; Energy Systems; Heating; Materials Science; Mathematical analysis; Optical and Electronic Materials; Phase change materials; Phase transitions; Phases; Retention; Structural Materials; Surface and Interface Science; Tellurium; Thermal energy; Thin Films; Transmission electron microscopy; Vacancies
• ISSN: 1884-4049; 1884-4057
• DOI: 10.1038/s41427-019-0140-z

Data retention ability and number of cycles are key properties of phase change materials in applications. Combining in situ heating transmission electron microscopy with ab initial calculations, we investigated the phase transitions of binary Sb–Te compounds. The calculations indicated that the vacancies in Te sites destroyed the framework of the cubic phase, which agrees well with the absence of cubic phases observed during in situ heating experiments when the Sb concentration exceeded 50%. In contrast, the vacancies in Sb sites stabilized the cubic structure. Further analysis of the charge density maps revealed that the distribution of antibonding electrons may be the origin of the driving force for structural transitions. Furthermore, our results also showed that reducing the vacancies greatly increased the phase transition temperatures of both the amorphous-cubic and cubic-trigonal phases and therefore may improve the data retention ability and cyclability of phase change materials. This result also implies that doping Sb–Te compounds may provide an approach to discover novel phase change materials by reducing the amount of vacancies. Data retention ability and cycle numbers are the decisive properties of phase change materials in applications. Combining in-situ heating transmission electron microscopy techniques with ab-initial calculations, we investigated the phase transitions of binary Sb-Te compounds. The results revealed that Sb vacancies stabilize the cubic framework while the Te vacancies tend to destroy it. This distinguished difference originates from the distribution of antibonding electrons. Reducing Sb vacancies greatly raised the phase transition temperatures of both amorphous-cubic and cubichexagonal phases and therefore may improve the data retention ability and the cyclability of phase change materials. Phase-change materials: More stable phases may improve data storage A way to stabilize information storage in the atomic structure of crystalline solids has been proposed by researchers in China. Atoms in some materials can exist in more than one arrangement, or phase, as determined by melting and freezing. Changing the phase at one specific point can allow these phase-change materials to store data. Xianqiang Liu from Beijing University of Technology, Zhitang Song from the Shanghai Institute of Micro-system and Information Technology and colleagues investigated the phase-change characteristics of alloys of antimony and telluride. Using