Study on CVD Growth of non van der Waals 2D Bi2O2Se and its Hybrid Integration for Optoelectronic Applications

Abstract

This thesis focuses on investigating the CVD growth of 2D non-van der Waals Bi2O2Se semiconductors and their structural, optical, electrical, and thermal properties, including photodetector applications. The thermal conductivity of CVD-grown ultrathin Bi2O2Se layers is calculated through an optothermal Raman measurement technique. The optical properties of 2D Bi2O2Se are thoroughly studied on various growth substrates. We discovered room-temperature exciton formation resulting in broadband absorption and photoluminescence in ultrathin Bi2O2Se established through spectroscopic studies and theoretical DFT calculations. We prepared heterostructures of Bi2O2Se with perovskite (CsPbBr3) nanocrystals as well as with 2D van der Waals type semiconductor MoS2 and investigated the effect of charge transfer on the luminescence and photo-conducting properties of the heterostructure. A photodetector is also fabricated based on the heterojunction, and the hybrid photodetector show superior photo-responsive properties compared to the bare Bi2O2Se-based devices. Free-standing ultrathin nanosheets of Bi2O2Se are chemically synthesized for photoconductivity study that discovers defect-induced negative persistent photoconductivity in highly defective Bi2O2Se that can convert into positive photoconductivity through vacuum annealing. These results are important for developing non-van der Waals heterostructures for ensuing applications