Hidden Direct Bandgap of Bi 2 O 2 Se by Se Vacancy and Enhanced Direct Bandgap of Bismuth Oxide Overlayer

• Published in: The journal of physical chemistry letters Vol. 15; no. 6; pp. 1590 - 1595
• Main Authors: Han, Sang Wook, Yun, Won Seok, Seong, Seungho, Tahir, Zeeshan, Kim, Yong Soo, Ko, Minji, Ryu, Sunmin, Bae, Jong-Seong, Ahn, Chang Won, Kang, Jeongsoo
• Format: Journal Article
• Language: English
• Published: United States 15-02-2024
• ISSN: 1948-7185; 1948-7185
• DOI: 10.1021/acs.jpclett.3c03223

The Bi
O
Se surfaces are well-known to possess 50% Se vacancies, yet they have shown no in-gap states within the indirect bandgap (∼0.8 eV). We have found that the hidden in-gap states arising from the Se vacancies in a 2 × 1 pattern induce a reduced direct bandgap (∼0.5 eV). Such a reduced direct bandgap is responsible for the high electron mobility of Bi
O
Se. Moreover, the Bi oxide overlayers of the Bi thin films, formed through air exposure and annealing, unexpectedly exhibit a large direct bandgap (∼2.1 eV). The simplified fabrication of Bi oxide overlayers provides promise for improving Bi
O
Se electronic devices and enhancing photocatalytic activity.