Hong Seok-Bo, Kim Dae-Kyoung, Chae Jimin, Kim Kiwoong, Jeong Kwangsik, Kim Jonghoon, Park Hanbum, Yi Yeonjin, Cho Mann-Ho
Department of Physics, Yonsei University, Seoul 03722, Republic of Korea.
Atomic-scale Surface Science Center, Yonsei University, Seoul 03722, Republic of Korea.
ACS Appl Mater Interfaces. 2020 Jun 10;12(23):26649-26658. doi: 10.1021/acsami.0c05165. Epub 2020 May 27.
Topological insulators (TIs) have become popular in the field of optoelectronic devices because of their broadband and high-sensitivity properties, which are attributed to the narrow band gap of the bulk state and high mobility of the Dirac surface state. Although perfectly grown TIs are known to exhibit strong stability against oxidation, in most cases, the existence of vacancy defects in TIs reacts to air and the characteristics of TIs is affected by oxidation. Therefore, changes in the band structure and electrical characteristics by oxidation should be considered. A significant change occurs because of the oxidation; however, the dependence of the photoresponse of TIs on oxidation has not been studied in detail. In this study, the photoresponsivity of oxidized BiSe films is enhanced, rather than degraded, after oxidation in air for 24 h, resulting in a maximum responsivity of 140 mA W. This responsivity is substantially higher than previously reported values for BiSe. Furthermore, a change in the photoresponse time of BiSe due to air exposure is systematically observed. Based on variations in the Fermi level and work function, using photoelectron spectroscopy, it is confirmed that the responsivity is improved from the junction effect of the Bi-based surface oxidized layer.
拓扑绝缘体（TIs）因其宽带和高灵敏度特性在光电器件领域受到欢迎，这些特性归因于体态的窄带隙和狄拉克表面态的高迁移率。尽管已知完美生长的TIs对氧化具有很强的稳定性，但在大多数情况下，TIs中存在的空位缺陷会与空气发生反应，TIs的特性会受到氧化的影响。因此，应考虑氧化导致的能带结构和电学特性的变化。氧化会导致显著变化；然而，TIs的光响应与氧化的相关性尚未得到详细研究。在本研究中，BiSe薄膜在空气中氧化24小时后，其光响应率增强而非降低，最大响应率达到140 mA/W。该响应率显著高于先前报道的BiSe值。此外，还系统地观察到BiSe因暴露于空气中而导致的光响应时间变化。基于费米能级和功函数的变化，利用光电子能谱证实，响应率的提高源于Bi基表面氧化层的结效应。
