Abinit界面效应对超薄Bi2Se3薄膜电子性质的影响
毕业论文关键词 拓扑绝缘体 密度泛函 超薄Bi2Se3薄膜 隧穿能隙 界面效应
Title Effects of interface on the electronic properties of ultrathin films of Bi2Se3
Abstract Topological insulator is a new quantum state. It is different from the conventional metal and insulator. The bulk of such material is an insulator with a finite excitation gap, while the surface is metallic and a chiral relation is kept between spin orientation and momentum. The surface state is protected by time reversal symmetry, which is not easily affected by the impurities and defects in the system. In this way, electrons transporting in topological insulators are dissipationless. Due to the unique surface properties of topological insulators, it has been a new research interest in the fields of materials science and condensed matter. It is also of great scientific value in the fields of fundamental research, quantum computation and spintronic devices. The electronic device units become even much thinner and smaller with the progress in microelectronic technology. However, for topological insulator films, when their thickness is small, the quantum tunneling effect will greatly degrade the metallic surface transport property. It is the focus of this thesis how preserves the great surface state properties in ultrathin topological insulator films. This thesis is consisted of three parts. In the first part, the background of topological insulator and the basic properties of Bi2Se3 are addressed; in the second part, we illustrate the theoretical foundation and the specific tools we used in our research. We also introduce density functional theory, the operation and use of Abinit software; the third part covers the third and the fourth chapters, which focuses on the influence of thickness and unilateral modification on the electronic structure of Bi2Se3. We found the single surface modification breaks the inversion symmetry of freestanding films, effectively suppresses quantum tunneling effect, and protects the excellent surface properties. Finally, we summarize the conclusions and make a prospect for the future application of this material. Keywords Topological insulator Density functional theory Ultrathin Bi2Se3 film Tunneling energy gap Interface effect
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