Metal-organic chemical vapor deposition of 2D Bi2O2Se single crystals on sapphire

Two-dimensional (2D) semiconductor Bi 2 O 2 Se has emerged as a promising channel material in post-Moore transistors. To realize its potential for industrial applications, a facile and reliable synthesis method for large-area, uniform, single-crystalline Bi 2 O 2 Se films on industrially compatible substrates is highly desired. However, existing approaches typically rely on solid-source evaporation, which suffers from poor precursor volatility and irreproducible mass transfer. Moreover, the epitaxial growth of 2D Bi 2 O 2 Se has been predominantly confined to non-scalable substrates such as perovskite oxides or mica. Here we report a metal-organic chemical vapor deposition (MOCVD) route to high-quality, single-crystalline Bi 2 O 2 Se films grown directly on industrially compatible r -plane sapphire. By employing triphenylbismuth and elemental selenium as volatile precursors, we achieve uniform and reproducible 2D film growth. Field-effect transistors fabricated from these films exhibit outstanding electrical performance, with an on/off ratio exceeding 10 5 , and the highest mobility of ∼228 cm 2 V −1 s −1 .