Controllable Synthesis of Novel Two-Dimensional Nonlayered β-Bi₂Te₄O₁₁ Flakes for Promising Optoelectronic Applications

Exploration of two-dimensional (2D) nonlayered materials is a significant work for developing the 2D materials family, owing to their intriguing physicochemical properties and promising applications in various fields. Herein, we present the controllable chemical vapor deposition (CVD) synthesis of nonlayered β-Bi2Te4O11 with a 2D morphology. It was revealed that the 2D growth of β-Bi2Te4O11 depends on the proper precursor. Moreover, the corresponding mechanism was demonstrated by density functional theory calculations. Moreover, the growth conditions of 2D β-Bi2Te4O11 were optimized by a machine learning (ML) strategy. The resultant 2D β-Bi2Te4O11 flakes with a large domain size (∼120 μm) and ultrathin thickness (∼9.5 nm) indicate promising applications of ML in guiding the CVD synthesis of 2D nonlayered materials. Compared with the bulk β-Bi2Te4O11 with an antiglass structure, the as-grown 2D β-Bi2Te4O11 shows a unique cation-ordering superstructure. In addition, the 2D β-Bi2Te4O11-based photodetector shows a prominent responsivity of 79.5 A W–1 at 375 nm. This work shows an efficient strategy for preparing 2D nonlayered materials and provides a brand-new platform to study the properties and applications of 2D nonlayered materials.