Vapour-liquid-solid-solid growth of two-dimensional non-layered β-BiO crystals with high hole mobility.

Currently, p-type two-dimensional (2D) materials lag behind n-type ones in both quantity and performance, hindering their use in advanced p-channel transistors and complementary logic circuits. Non-layered materials, which make up 95% of crystal structures, hold the potential for superior p-type 2D materials but remain challenging to synthesize. Here we show a vapour-liquid-solid-solid growth of atomically thin (<1 nm), high-quality, non-layered 2D β-BiO crystals on a SiO/Si substrate. These crystals form via a transformation from layered BiOCl intermediates. We further realize 2D β-BiO transistors with room-temperature hole mobility and an on/off current ratio of 136.6 cm V s and 1.2 × 10, respectively. The p-type nature is due to the strong suborbital hybridization of Bi 6s6p with O 2p at the crystal's M-point valence band maximum. Our work can be used as a reference that adds more 2D non-layered materials to the 2D toolkit and shows 2D β-BiO to be promising candidate for future electronics.