Nature Materials nature materials https://doi.org/10.1038/s41563-025-02141-w Article Vapour–liquid–solid–solid growth of two-dimensional non-layered β-Bi 2 O 3 crystals with high hole mobility Yunhai Xiong  1,6 , Duo Xu  1,6 , Yousheng Zou 1,6 , Lili Xu 1 , Yujie Yan 2 , Jianghua Wu 2 , Chen Qian 3 , Xiufeng Song  1 , Kairui Qu 1 , Tong Zhao 1 , Jie Gao 1 , Jialin Yang 1 , Kai Zhang  4 , Shengli Zhang 1 , Peng Wang  2,5 , Xiang Chen  1 & Haibo Zeng  1 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-Bi 2 O 3 crystals on a SiO 2 /Si substrate. These crystals form via a transformation from layered BiOCl intermediates. We further realize 2D β-Bi 2 O 3 transistors with room-temperature hole mobility and an on/ off current ratio of 136.6 cm 2 V −1 s −1 and 1.2 × 10 8 , respectively. The p-type nature is due to the strong suborbital hybridization of Bi 6s 2 6p 3 with O 2p 4 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-Bi 2 O 3 to be promising candidate for future electronics. In the past few decades, silicon-based transistors have been scaling down according to Moore’s Law. However, as the size of transistors has decreased to the nanometre scale, short-channel effects, such as reduced carrier mobility, increased leakage current and higher static power consumption, have become more pronounced 1,2 . In the post-Moore era, an urgent requirement exists to develop new architec- tures and materials. Among the potential options, two-dimensional (2D) semiconductors have been considered ideal channel materials owing to their atomic thickness, high mobility and strong gate control 3–5 . Unfortunately, most 2D semiconductors are n-type or ambipolar due to the strong electron doping caused by interfacial charge impurities and internal structural defects 6,7 . Moreover, the mobility of p-type 2D semiconductors is lower than that of n-type ones, often by ~1–2 orders of magnitude 4,8 . Many p-type 2D semiconductors have poor stability, which is not conducive to device processing and long-term service 9,10 . This creates an imbalance between n-type and p-type 2D semiconductors, which limits their usefulness in high-performance p-channel transistors, complementary integrated circuits and junc- tion devices 11 . As a result, an urgent need exists to develop new p-type 2D semiconductors with excellent performance and reliability; this is currently a priority research area with substantial implications for future electronics 12 . Received: 2 July 2022 Accepted: 15 January 2025 Published online: xx xx xxxx Check for updates 1 MIIT Key Laboratory of Advanced Display Materials and Devices, Jiangsu Engineering Research Center for Quantum Dot Display, Institute of Optoelectronics & Nanomaterials, School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing, China. 2 National Laboratory of Solid State Microstructures, Jiangsu Key Laboratory of Artificial Functional Materials, College of Engineering and Applied Sciences and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, China. 3 Department of Chemistry, University of Warwick, Coventry, UK. 4 CAS Key Laboratory of Nano-Bio Interface & Key Laboratory of Nanodevices and Applications, i-Lab, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou, China. 5 Department of Physics, University of Warwick, Coventry, UK. 6 These authors contributed equally: Yunhai Xiong, Duo Xu, Yousheng Zou. e-mail: xiangchen@njust.edu.cn; zeng.haibo@njust.edu.cn