Bandgap Tuning of β‐(Al_xGa_1‐x)₂O₃ Nanosheets via Liquid Metal Interface Engineering

Abstract Precise engineering of the electronic band structure in 2D metal oxides is essential for advancing optical and electronic nanodevices, yet achieving compositional control at the nanoscale remains challenging. Here, a low‐temperature liquid metal‐based synthesis method is used to fabricate β‐(Al_xGa_1‐x)₂O₃ nanosheets with tunable composition (x = 0–0.88). This approach enables selective aluminium enrichment in nanosheets while preserving the monoclinic crystal structure and adopting the (−201) orientation, similar to conventional β‐Ga₂O₃ thin films. The synthesized nanosheets exhibit large lateral dimensions (>100 µm) and an average thickness of 3.2 ± 0.5 nm, making them suitable for nanoscale device applications. By varying the Al content from 0 to 10 at% in the liquid metal, the bandgap is tuned from 4.50 eV (pure β‐Ga₂O₃) to 6.41 eV (β‐(Al_0.88Ga_0.12)₂O₃). Molecular dynamics simulations provide insights into the Al enrichment mechanism at the liquid metal interface. The β‐(Al_xGa_1‐x)₂O₃ nanosheets retain key β‐Ga₂O₃ characteristics, including self‐trapped hole formation, ensuring structural and electronic integrity. The liquid metal synthesis method overcomes limitations of conventional deposition techniques, offering a scalable approach for tailoring 2D metal oxide properties and enabling bandgap‐engineered optoelectronic applications.