Cathodoluminescence studies of sp2-hybridized BN thin films and monolayers grown by vapor phase epitaxy

Hexagonal (h)BN, a 2D layered compound with sp² bonding (AA’ stacking), exhibits efficient excitonic emission at ~215 nm despite being an indirect bandgap semiconductor (~6 eV), making it ideal for deep ultraviolet (DUV) applications. Other sp²-bonded polytypes, such as rhombohedral (r)BN (ABC stacking) and Bernal (b)BN (AB stacking), exhibit luminescence around 215 nm and 207 nm, respectively. Monolayer hBN (mBN) has been reported to have a direct bandgap and emit around 205 nm. Vapor-phase growth methods, promising for large-area production, have been used to grow hBN, rBN, bBN, and mBN phases. Shizuoka University has achieved high-quality sp²-BN thin films with excitonic emission via halide vapor phase epitaxy, while the University of Nottingham has successfully grown mBN using molecular beam epitaxy. This talk will focus on the DUV emission properties of these sp²-bonded BN films and monolayers, evaluated using cathodoluminescence spectroscopy.