应变工程中Bi(111)薄膜的半导体-半金属转变及其机理  

Strain-Engineered Semiconductor to Semimetallic Transition and Its Mechanism in Bi(111) Film

作　　者：任师浩 刘永利 孟凡顺 祁阳 REN Shihao;LIU Yongli;MENG Fanshun;QI Yang(School of Materials Science and Engineering,Northeastern University,Shenyang 110819,China;School of Science,Liaoning University of Technology,Jinzhou 121001,China)

机构地区：[1]东北大学材料科学与工程学院,沈阳110819 [2]辽宁科技大学理学院,锦州121001

出　　处：《金属学报》2022年第7期911-920,共10页Acta Metallurgica Sinica

基　　金：国家自然科学基金项目No.61971116~~。

摘　　要：基于第一性原理,系统研究了不同层数Bi(111)薄膜的几何结构和能带性质,以及双轴应变对Bi(111)薄膜结构与电学性能的调控作用。研究结果表明:Bi(111)薄膜的几何结构以及能带性质具有厚度依赖性。随着厚度的增加,薄膜晶格常数增大,屈曲高度降低,表面能增加,带隙减小,并在3个双层时由半导体性质转变为半金属性质;对1个双层Bi(111)薄膜施加拉伸应变,可诱发间接带隙到直接带隙的转变以及能带反转;施加压缩应变可诱发半导体到半金属性质的转变,通过近带边电子轨道的成键性质分析,揭示了成键态和反键态对应变的不同响应速率,引起了导带底的转移,从而导致了半导体到半金属转变。类似的半导体到半金属转变也可在应变作用下的2~5个双层厚Bi(111)薄膜中预测到。应变也可调节Bi(111)薄膜的电子和空穴的有效质量,从而可能影响薄膜传输特性。Bi is a key semimetallic element with strong spin-orbit coupling characteristics, long Fermi wavelengths, quantum size effects, and competitive structural phases. Its spin-orbit coupling can induce the metal surface state of Bi thin film, which is completely different from its bulk properties, indicating that thin Bi film has important research significance in the control of the transmission performance of semiconductor sensors. The biaxial strain deformation and film thickness can induce the transition from semiconductors to semimetals and changes in topological properties. However, the current critical transition thickness obtained using different methods is contentious, and the inherent transition mechanism remains unclear. In this work, the effect and affecting mechanism of biaxial strain on the geometric and band structures of Bi thin films with different thicknesses of Bi thin films were systematically studied and discussed using a first-principles method based on density functional theories. The results show that the band and geometric structures of Bi(111) films are strongly correlated to the thickness. With the increase in the number of atomic layers, the lattice constant increases, the buckling height decreases, the surface energy increases, and the energy bandgap decreases, where a transition of the films from semiconductor to semimetal occurs at the critical thickness of three bilayers(BLs). The application of tensile strain to the one-BL Bi film can induce the transition of energy bandgap from indirect to direct semiconductor accompanied with a band inversion, whereas the compressive strain can induce the transition from semiconductor to semimetal. The analysis of the bond nature of the near-band-edge electronic orbitals revealed that the transition of the semiconductor to the semimetallic state originates from the transition of the conduction band minimum induced by the different response rates of the bonding and antibonding states of the band edge electrons to the strain. A similar transition can b

关 键 词：Bi薄膜 应变 能带结构 第一性原理方法 

分 类 号：O484.4[理学—固体物理]