Laser‐assisted in situ fabrication of atomically thin Ga ₂ O ₃ films for dielectric applications

Two‐dimensional (2D) gallium oxide (Ga 2 O 3 ) has emerged as a high‐ κ dielectric material for optoelectronic applications due to its ultra‐wide bandgap and large‐scale productivity. However, the usage of thermal treatment during the liquid‐metal‐assisted fabrication process could degrade the quality of channel materials. Here, we report a laser‐assisted in situ oxidation method combined with a confinement template‐assisted squeeze technique to fabricate centimeter‐scale 2D atomically thin Ga 2 O 3 films from liquid gallium metal surfaces at room temperature. This approach avoids thermal damage to vulnerable materials. The laser‐accelerated oxidation mechanism is elucidated as photocatalytic oxidation of initial Ga/Ga 2 O 3− x surface through the integration of multi‐wavelength laser radiation experiments and density functional theory calculations. We further demonstrate top‐gated field‐effect transistors (FETs) using black phosphorus (BP) and MoS 2 as channel materials, with thin‐film Ga 2 O 3 as the gate dielectrics. BP‐based FETs show gate‐tunable mid‐infrared photoresponse with responsivity at the order of 0.1 A·W −1 level. MoS 2 ‐based FETs exhibit a photo‐detectivity of 6.8 × 10 12 Jones in the visible‐light spectrum, an on/off ratio over 10 8 , a subthreshold swing of 73.6 mV decade −1 , and gate leakage currents below 4 × 10 −6 A cm −2 at 8 MV cm −1 . This room‐temperature laser‐oxidation approach enables scalable integration of ultrathin oxide dielectrics with sensitive 2D materials for next‐generation nanoelectronics.