The Novel Two-Dimensional Materials and Heterostructures Thin Films of Electronic Structure
Pei-Yu Chuang1*, Shu-Hsuan Su1, Shen-Wen Chen1, Cheng-Maw Cheng2, Tay-Rong Chang3, Jung-Chun A. Huang1
1Department of physics, National Chung Kung University, Tainan, Taiwan
2National Synchrotron Radiation Research Center, Hsinchu, Taiwan
3Department of physics, National Tsing Hua University, Hsinchu, Taiwan
* presenting author:Pei-Yu Chuang, email:steven_enjoy@msn.com
Three-dimensional topological insulator has led to intense research owing to the potential applications of these materials in the field of spintronics and quantum computing. TIs are insulating materials in the bulk, which host metallic surface states in the energy gap with a Dirac-cone-like dispersion. These states are protected by time-reversal symmetry that show spin-momentum locking and leads to suppression of the electron backscattering by defects. The corresponding topological invariants dictate that there must be an odd number of such states intersecting the Fermi level between each pair of surfa
ce time-reversal invariant momenta. The bismuth- chalchogenide family of topological insulators are just one of these so-called topological surface states creating a single Dirac cone in the Brillouin zone centre. More importantly, additional pairs of two-dimensional, almost parabolic states emerge in the vicinity of the bulk conduction band, which develop large Rashba-type splitting. Since large spin-orbit coupling is prerequisite for a material to exhibit topologically protected states, bismuth is a primary candidate and bismuth bilayers have become under intense study. Which are now regarded as a prototype of an elemental 2D TIs. Recently, investigating step edges of a Bi(111) surface have aimed to prepare bismuth bilayers by using molecular beam epitaxy or exfoliation.
In this report, we present a simple and controllable approach, which is based on exposing c single crystal thin film to a flux of atomic hydrogen. Angle-resolved photoemission spectroscopy (ARPES) and other surface sensitive techniques such as x-ray photoemission spectroscopy (XPS), low energy electron diffraction (LEED). Bi2Se3 thin films were transferred into ultra-high vacuum prepare chamber base pressure around 1E-9 torr and decapping protect layer of Se by thermal heated. ARPES measurements indicate a well contrasted sharp TIs surface state. Atomic hydrogen was generated by a thermal cracker source, during the operation of atom source, the hydrogen partial pressure in the chamber was PH2 is 1.2E-7 torr. For the quantification of the exposure of the sample, the Langmuir (L) units (1L=1E10-6 torr) in the following, which is proportional to the amount of hydrogen atoms interacting with the sample that was kept at room temperature. It was obtained electronic band structure of single bismuth bi layer (111) terminated Bi2Se3 (0001) surface that the TIs surface state of the system features the Dirac point at about 0.4 eV below the Fermi level, as in a Rashba type splitting


Keywords: Topological insulator, ARPES, STM