Abstract:

Two-dimensional (2D) semiconductors offer an atomic thickness that facilitates superior gate field penetration and enables transistors to maintain shrinking with suppressed short-channel effects, thereby being considered as channel materials for future transistors in the post-Moore era. As a member of high-mobility 2D semiconductors, the air-stable Bi₂O₂Se with a moderate bandgap has drawn significant attention. Distinguished from other 2D materials, Bi₂O₂Se can be oxidized layer-by-layer to form a high-k native-oxide dielectric, Bi₂SeO₅, with an atomically sharp interface, similar to Si/SiO₂ in the semiconductor industry. These characteristics make Bi₂O₂Se an ideal material platform for fabricating various devices with excellent performance, such as transistors, thermoelectrics, optoelectronics, sensors, flexible devices and memory devices. To realize advanced applications of 2D Bi₂O₂Se, it is essential to develop scalable and high-quality preparation methods with relatively low cost. Chemical vapor deposition (CVD) has shown promise in meeting these requirements. Over the past years, CVD has been widely used to synthesize 2D Bi₂O₂Se despite some remaining challenges. In this review, we summarize the recent progress in the controlled growth of 2D Bi₂O₂Se via the CVD method. We begin by introducing the crystal structure and properties of Bi₂O₂Se. Next, we focus on the morphology control of 2D Bi₂O₂Se, including various nucleation modes and different dimensionalities by carefully manipulating the CVD process. In terms of nucleation modes, in-plane and vertical epitaxial growth of Bi₂O₂Se, achieved by controlling the interaction between epitaxial layer and substrate, are reviewed. Wafer-scale continuous Bi₂O₂Se film facilitates the device integration while vertical 2D fins pave the way for fabricating high-performance fin field-effect-transistors (FinFET). As for the dimensionality control, the transition from 2D nanoplates to 1D nanoribbons is investigated. Parameters such as precursor ratio, growth temperature and types of catalyst play a key role in such transition. We then discuss the construction of ordered arrays of Bi₂O₂Se with the above morphology by selective growth and post treatment for potential device integration. In addition, we highlight the electrical quality improvement of the grown material via defect control and strain release. For example, both the Se poor growth condition and the out-of-plane strain-free growth contribute to higher mobility of Bi₂O₂Se. Lastly, we propose potential strategies for precise control of Bi₂O₂Se structures and quality. In order to meet the demands of advanced electronic applications, more efforts are expected to made to achieve uniform, transferable and site-specific preparation of high-quality single-crystal Bi₂O₂Se on a large scale.

Key words: Bi₂O₂Se, Chemical vapor deposition, Nucleation mode, Dimensionality, Array, Electrical quality