Electronic Band Structure of the Single Bi-bilayer Produced by Hydrogen-radical etching on Bi2Se3(0001)

• Main Authors: Xiao, Fu Zhong, 蕭富中
• Other Authors: Lin, Deng Sung
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/31963123991702238397

碩士 === 國立清華大學 === 物理系 === 104 === Free standing Bi-bilayer has been predicted as a two dimensional topological insulator. Therefore, how to prepare a high quality Bi-bilayer thin film becomes a hot research topic. The electronic band structure of the MBE single Bi-bilayer on the Bi2Se3(0001) surface had been revealed by Lin Miao et al. Recently, Roozbeh Shokri et al. suggested that the samples with high single Bi-bilayer coverage can be produced by the hydrogen radical etching process and that the band structure of H-etching Bi-bilayer/Bi2Se3(0001) system is similar to that grown by MBE. However, the band structure of the H-etching Bi-bilayer/Bi2Se3(0001) system had not been measured before. In this work, we will measure its band structure by angle resolved photoemission.We have first prepared the Bi-bilayer by H-etching of the cleaved Bi2Se3(0001) surface. Then we studied its surface morphology and the atomic structure by scan tunneling microscopy (STM) and have analyzed stoichemistry on the surface by means of the ultraviolet photoemission spectroscopy (UPS) and the X-ray photoemission spectroscopy (XPS) with photo energy 55 eV and 380 eV respectively. By combining the results from STM, XPS and UPSs, we can conclude that, the Bi-bilayer coverage on the deuterium radical etching Bi2Se3(0001) is 1.30±0.02 Bi-bilayer when the effect of deuterium radical etching was saturated at the expense of about 1.5 Quintuple layer (QL) The coverage of single Bi-bilayer is about 70 % on the top of sample. Our results from STM, XPS and UPS provide not only a good evidence for our first conclusion but also a reference for the Bi deposition rate estimation for the ARPES experiment. In our ARPES experiment, the Fermi-level E_F was first calibrated by Ag(111) crystal and the thickness of Bi film was estimate by STM, UPS and XPS. The ARPES results show that, no matter which well performance single Bi-bilayer growth mode we chosed, by low temperature (200 K) MBE process or room temperature hydrogen radical-etching process, the electronic band structure is the same ”. The reasons were two folds, first, the binding energy difference 〖∆E〗_B between Dirac point D_B and D_S are 0.3 eV. Second, the momentum difference 〖∆k〗_(||) between spin up state electron and spin down state electrons at E_B=0.000 eV and E_B=0.540 eV are 〖∆k〗_(||)≅0.235 Å^(-1) 〖∆k〗_(||)≅0.215 Å^(-1). In conclusion, we can get two points. First, “ the Bi-bilayer coverage on the deuterium radical etching Bi2Se3(0001) will be 1.30±0.02 Bi-bilayer when the effect of deuterium radical etching was saturate ”. Second, “ no matter which well performance single Bi-bilayer growth mode we chosed, by low temperature (200 K) MBE process or room temperature hydrogen radical-etching process, the electronic band structure is the same ”.