Large-scale synthesis of atomically thin ultrawide bandgap β-Ga₂O₃ using a liquid gallium squeezing technique

β-Ga₂O₃, an emerging ultrawide bandgap (UWBG) semiconductor, offers promising properties for next-generation power electronics, chemical sensors, and solar-blind optoelectronics. Scaling down of β-Ga₂O₃ to the atomic level affords the advantages of two-dimensional (2D) materials, while maintaining the inherent properties of the parent bulk counterpart. Here, we demonstrate a simple approach to synthesize ultrathin millimeter-size β-Ga₂O₃ sheets using a liquid gallium squeezing technique. The GaO_x nanolayer produced by stamping liquid gallium under the Cabrera–Mott oxidation was converted into few-atom-thick β-Ga₂O₃ via thermal annealing under atmospheric conditions. This approach was also applied to various substrates such as SiO₂, Si, graphene, quartz, and sapphire to heteroepitaxially synthesize 2D β-Ga₂O₃ on a target substrate. Finally, we propose a patterning strategy combining the squeezing technique with conventional lithography to obtain a β-Ga₂O₃ layer with a controllable thickness and shape. Our synthetic method has the potential to overcome the limitations of conventional β-Ga₂O₃ growth methods, paving a path for applications in UWBG-based (opto-)electronics with a high throughput in a cost-effective manner.