外尔半金属WTe_(2)/Ti异质结的热稳定性拉曼散射研究  

Thermal stability study of Weyl semimetal WTe_(2)/Ti heterostructures by Raman scattering

作　　者：刘娜 王译 李文波 张丽艳 何世坤 赵建坤 赵纪军 Liu Na;Wang Yi;Li Wen-Bo;Zhang Li-Yan;He Shi-Kun;Zhao Jian-Kun;Zhao Ji-Jun(Key Laboratory of Materials Modification by Laser,Ion and Electron Beams,Ministry of Education,School of Physics,Dalian University of Technology,Dalian 116024,China;School of Chemical Engineering,Dalian University of Technology,Dalian 116024,China;Zhejiang Hikstor Technology Company,Hangzhou 311305,China)

机构地区：[1]大连理工大学物理学院,三束材料改性教育部重点实验室,大连116024 [2]大连理工大学化工学院,大连116024 [3]浙江驰拓科技有限公司,杭州311305

出　　处：《物理学报》2022年第19期291-298,共8页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:12074052);辽宁省自然科学基金优秀青年基金计划(批准号:2021-YQ-06);中央高校基本科研业务费专项资金(批准号:DUT20LK30)资助的课题。

摘　　要：外尔半金属Td-WTe_(2)是一种新型的拓扑量子材料,具有很强的自旋轨道耦合作用和独特的拓扑能带结构,被认为是一种非常有潜力的自旋电子材料.通过构造WTe_(2)/Ti异质结构,能够解决原本在WTe_(2)上无法直接制备出具有垂直磁各向异性铁磁层的难题.与现有半导体工艺相兼容,器件集成需要经受高温处理过程,因此WTe_(2)/Ti的热稳定性对于实际器件制备和应用至关重要.然而,WTe_(2)/Ti界面的热稳定性目前仍然不清楚.本文利用显微拉曼散射技术系统研究了不同温度退火后的WTe_(2)/Ti异质结的热稳定性,发现WTe_(2)和Ti的界面热稳定性与WTe_(2)纳米片的厚度相关,WTe_(2)纳米片厚度适当增加,WTe_(2)/Ti异质结更加稳定.此外,高温退火会导致更加强烈的界面反应,在473 K退火30 min后,WTe_(2)(12nm)与Ti发生明显界面反应,生成Ti-Te化合物,该现象与高分辨透射电子显微镜测量和元素分析结果高度一致.研究结果为进一步探究WTe_(2)/Ti界面对于自旋轨道转矩效应的影响提供有用信息,激发基于WTe_(2)等拓扑材料的低功耗自旋器件研究.Weyl semimetal Td-phase WTe_(2),a novel topological matter,possesses a strong spin-orbit coupling and non-trivial topological band structure,and thus becomes a very promising superior spin current source material.By constructing the WTe_(2)/Ti heterostructures,the issue that the ferromagnetic layer with perpendicular magnetic anisotropy cannot be directly prepared on WTe_(2)layer can be well addressed,and meet the requirements for high-performance spin-orbit torque devices.To be compatible with the semiconductor technology,the device integration usually involves a high temperature process.Therefore,the thermal stability of WTe_(2)/Ti is critical for practical device fabrication and performance.However,the thermal stability of WTe_(2)/Ti interface has not been very clear yet.In this work,the micro-Raman scattering technique is used to systematically study the WTe_(2)/Ti interface annealed at different temperatures.It is found that the thermal stability of the interface between WTe_(2)and Ti is related to the thickness of WTe_(2)flake;appropriate increase of the WTe_(2)thickness can lead to the improvement of thermal stability in WTe_(2)/Ti heterostructures.In addition,high temperature annealing can cause a significant inter facial reaction.After annealed at 473 K for 30 min,the interface between WTe_(2)(12 nm) and Ti changes dramatically,leading to the formation of Ti-Te interface layer.This observation is highly consistent with the observations by high-resolution transmission electron microscopy and the elemental analysis results as well.This study will provide useful information for further exploring the influence of the WTe_(2)/Ti interface on the spin-orbit torque effect,and greatly invigorate the research area of energy efficient spintronic devices based on WTe_(2)and other novel topological materials.

关 键 词：外尔半金属WTe_(2) WTe_(2)/Ti异质结 热稳定性 拉曼散射 

分 类 号：O469[理学—凝聚态物理]