Programmable interfacial band configuration in WS2/Bi2O2Se heterojunctions

• Main Authors: Zhang, Hanwen, Fu, Jianhui, Carvalho, Alexandra, Poh, Eng Tuan, Chung, Jing-Yang, Feng, Minjun, Chen, Yinzhu, Wang, Bo, Shang, Qiuyu, Yang, Hengxing, Zhang, Zheng, Lim, Sharon Xiaodai, Gao, Weibo, Gradečak, Silvija, Qiu, Cheng-Wei, Lu, Junpeng, He, Chunnian, Sum, Tze Chien, Sow, Chorng Haur
• Other Authors: School of Physical and Mathematical Sciences
• Format: Article
• Language: English
• Published: 2024
• Subjects: Physics; 2D materials; Band alignment
• Online Access: https://hdl.handle.net/10356/179498
• Institution: Nanyang Technological University

van der Waals heterojunctions based on transition-metal dichalcogenides (TMDs) offer advanced strategies for manipulating light-emitting and light-harvesting behaviors. A crucial factor determining the light-material interaction is in the band alignment at the heterojunction interface, particularly the distinctions between type-I and type-II alignments. However, altering the band alignment from one type to another without changing the constituent materials is exceptionally difficult. Here, utilizing Bi2O2Se with a thickness-dependent band gap as a bottom layer, we present an innovative strategy for engineering interfacial band configurations in WS2/Bi2O2Se heterojunctions. In particular, we achieve tuning of the band alignment from type-I (Bi2O2Se straddling WS2) to type-II and finally to type-I (WS2 straddling Bi2O2Se) by increasing the thickness of the Bi2O2Se bottom layer from monolayer to multilayer. We verified this band architecture conversion using steady-state and transient spectroscopy as well as density functional theory calculations. Using this material combination, we further design a sophisticated band architecture incorporating both type-I (WS2 straddles Bi2O2Se, fluorescence-quenched) and type-I (Bi2SeO5 straddles WS2, fluorescence-recovered) alignments in one sample through focused laser beam (FLB). By programming the FLB trajectory, we achieve a predesigned localized fluorescence micropattern on WS2 without changing its intrinsic atomic structure. This effective band architecture design strategy represents a significant leap forward in harnessing the potential of TMD heterojunctions for multifunctional photonic applications.