Epitaxial Growth of 2D Ultrathin Metastable γ-Bi2O3 Flakes for High Performance Ultraviolet Photodetection

Ultraviolet detection is of great significance due to its wide applications in the missile tracking, flame detecting, pollution monitoring, and so on. The nonlayered semiconductor γ-Bi 2 O 3 is a promising candidate toward high-performance UV detection due to the wide bandgap, excellent light sensitivity, environmental stability, nontoxic and elemental abundance properties. However, controllable preparation of ultrathin 2D γ-Bi 2 O 3 flakes remains a challenge, owing to its nonlayered structure, metastable nature, and other competing phases. Moreover, the UV photodetectors based on 2D γ-Bi 2 O 3 flake have not been implemented yet. Here, ultrathin (down to 4.8 nm) 2D γ-Bi 2 O 3 flakes with high crystal quality are obtained via a van der Waals epitaxy method. The as-synthesized single-crystalline γ-Bi 2 O 3 flakes show a body-centered cubic structure and grown along (111) lattice plane as revealed by experimental observations. More importantly, photodetectors based on the as-synthesized 2D γ-Bi 2 O 3 flakes exhibit promising UV detection ability, including a responsivity of 64.5 A W −1 , a detectivity of 1.3 × 10 13 Jones, and an ultrafast response speed (τ rise ≈ 290 µs and τ decay ≈ 870 µs) at 365 nm, suggesting its great potential for various optoelectronic applications.