Investigation on the carrier dynamics and energy band of the CVD-grown large area WS2/Bi2O2Se heterostructure

Abstract

Bismuth oxyselenide (Bi₂O₂Se) emerged as a prominent member of the quasi-2D layered material family, possesses appealing characteristics for optoelectronic applications including impressive environmental stability and high carrier mobility. Recently, although significant advancements have been made in the initial research on the optoelectronic characteristics of Bi₂O₂Se-based heterostructures, there remains a lack of comprehensive study on the carrier dynamics and energy band within these structures. In this work, large-area (1 cm × 1 cm) continuous Bi₂O₂Se and monolayer WS₂ films were grown by chemical vapor deposition (CVD) method, and the related WS₂/Bi₂O₂Se heterostructures were successfully constructed. Triple decay processes with lifetimes of${\tau }_1$ ∼ 298 ps, ${\tau }_2$∼37 ps and${\tau }_3$ ∼ 1.58 ns are observed through time-resolved photoluminesce (TRPL), which were attributed to the recombination of neutral excitons, trions, and interlayer excitons, respectively. Then, the energy band structure was investigated through x-ray photoelectron spectroscopy, revealing a type-Ⅱ band alignment at the heterointerface. The valence band offset was 0.19 eV, while conduction band offset was approximately 1.09 eV as confirmed by ultraviolet photoelectron spectroscopy. As a result, the WS₂/Bi₂O₂Se junction enhances charge transfer and interlayer interactions by the aid of interface build-in electric field. These results showcase the potential of integrating Bi₂O₂Se with other 2D semiconductors to form heterostructures possessing novel charge dynamic behaviors, and provide valuable understanding into the functionality of optoelectronic devices that rely on these 2D heterostructures.