锑碲合金Sb_(2)Te_(3)的异相同质结构设计  

Designing Sb_(2)Te_(3) heterophase homostructure

作　　者：王晓哲 张航铭 王旭东[1] 王疆靖 马恩 张伟[1] Xiaozhe Wang;Hangming Zhang;Xudong Wang;Jiangjing Wang;En Ma;Wei Zhang(Center for Alloy Innovation and Design,State Key Laboratory for Mechanical Behavior of Materials,Xi’an Jiaotong University,Xi’an 710049,China)

机构地区：[1]西安交通大学金属材料强度国家重点实验室,材料创新设计中心,西安710049

出　　处：《科学通报》2022年第22期2662-2671,共10页Chinese Science Bulletin

基　　金：国家自然科学基金(61774123,52150710545);教育部高等学校学科创新引智计划(BP2018008)资助。

摘　　要：半导体锑碲合金Sb_(2)Te_(3)是实现高性能相变存储与类脑计算的一种关键母体材料,其亚稳态立方相具有占格点高达1/6以上且随机分布的空位,具备安德森绝缘体性质.而Sb_(2)Te_(3)的稳态结构为菱方六角相,是一种典型的强拓扑绝缘体材料.但由于六角相Sb_(2)Te_(3)存在自发掺杂行为,其体相通常呈金属性而非绝缘性,从而掩盖了其拓扑非平庸的狄拉克表面态性质.本工作提出一种基于Sb_(2)Te_(3)的异相同质结构的新概念,原理上可同时利用该材料的拓扑性质与安德森绝缘性质从而实现超低损耗的电子输运.本文在分子束外延制备的六角相Sb_(2)Te_(3)薄膜中,利用透射电子显微镜中的聚焦电子束辐照驱动薄膜体相区域的六角相至立方相结构相变,并原位观察了空位无序化在其中起到的关键性作用.通过第一性原理计算,结果表明六角相Sb_(2)Te_(3)的能量随着空位层空位浓度的降低而快速上升,在空位浓度减小至50%~70%时触发原子堆垛迁移,从而形成立方相结构.临界空位浓度的大小主要受沿空位层垂直方向压应力的影响.结合实验与计算结果,本文证实了Sb_(2)Te_(3)异相同质结构的界面附近不存在明显的晶格错配,为后续制备Sb_(2)Te_(3)异相同质结构宏观样品,以及探索拓扑物理与安德森电子局域化之间的相互作用提供了指导.Antimony sesquitelluride(Sb_(2)Te_(3))is the most important hosting material for the development of high-performance phasechange memory and brain-like computing technology.This material has two crystalline phases,namely,the metastable cubic rock-salt structure with 1/6 atomic sites taken by randomly distributed vacancies,and the stable rhombohedral phase with layered structures and vacant gaps in hexagonal stacking.The former is an Anderson insulator(AI)and serves as the key ingredient for memory applications,while the latter is a prototypical topological insulator(TI).In this work,we propose a new heterophase homostructure concept for Sb_(2)Te_(3),which in principle could utilize both the topologically protected surface state of the rhombohedral phase and the Anderson localization features of the cubic phase in the bulk interior to achieve ultralow-loss electron transport.To sustain the topological surface state,the edges of the device should be kept in rhombohedral phase with the thickness larger than~4 nm.The bulk interior of the sample should be transformed into cubic phase with strong electron localization.According to our density functional theory(DFT)results,the layered atomic building blocks for the two phases are quite similar,though their stacking sequence and degree of structural disorder are different.Thanks to the similar structure and mass density of the two phases,lattice mismatch is not expected to be present at the interface of the heterophase homostructure,superior to heterostructures made of different materials.To lend support to this heterophase homostructure concept,we have prepared a~500 nm thick rhombohedral Sb_(2)Te_(3)thin film on a silicon substrate via molecular beam epitaxy(MBE)and made an attempt to induce the phase transition in its bulk interior.A cross-sectional specimen for transmission electron microscopy(TEM)experiments was prepared by a dual beam focused ion beam(FIB)system.The TEM specimen along the electron beam direction was~80 nm.For standard TEM observation in short time,t

关 键 词：相变材料 拓扑绝缘体 Sb_(2)Te_(3) 原位表征 空位无序化 异相同质结构 

分 类 号：TG146.18[一般工业技术—材料科学与工程]