Photophysics of Distinguished Defect States in Bi₂O₂Se Thin Films

As a leading candidate for next-generation electronics, high-performance 2D Bi₂O₂Se has garnered significant interest in the scientific community. However, the understanding of its defect mechanisms remains elusive, hindering the development of further functionalities. In this study, we utilized Raman spectroscopy and ultrafast pump-probe experiments to investigate Bi₂O₂Se thin films prepared via a solution-based technique. By comparing carrier decay times under low and high fluences in 25 nm- and 115 nm-thick films, we proposed the defect mechanisms associated with two common defects in the thicker film: Se vacancies and Se-Bi antisites, which exhibit shallow donor and deep donor behaviors, respectively. Additionally, Se-Bi antisites became prominent under higher fluences. Our insights into these defect mechanisms offer valuable guidance for defect engineering in high-power electronics.