Terahertz spectroscopy study of the topological insulator Bi2Se3 thin film

• Main Author: Ng, Yi Ming
• Other Authors: Chia Ee Min, Elbert
• Format: Final Year Project
• Language: English
• Published: 2016
• Subjects: DRNTU::Science::Physics::Optics and light; DRNTU::Science::Physics::Atomic physics::Solid state physics
• Online Access: http://hdl.handle.net/10356/67968
• Institution: Nanyang Technological University

Topological insulators are a distinct class of materials with insulating bulk states and conducting surface states, and they are a major focus for research in Condensed Matter Physics. In this project, a topological insulator, Bi2Se3 thin film, is grown by molecular beam epitaxy (MBE) which is 32 QL thick. It is investigated using Terahertz-Time Domain Spectroscopy (THz-TDS). Bi2Se3 has been around since the 1950s and it is only until recently that more attention was paid to it as a topological insulator. It shows particular promise for technological applications such as a THz photodetector. The temperature dependence (15 – 300 K) of the optical conductivity was obtained for a range of spectroscopic frequencies (0.5 – 2.5 THz) and fitted to a Drude-Lorentz model. The Drude response was attributed to the presence of the surface states in Bi2Se3, and the Lorentz response was attributed to the semiconductor nature of the bulk state of Bi2Se3.