Lattice Matching Engineering Driven Growth of Large‐Area 2D CeO₂ for High‐Performance Photodetection

Abstract Few rare‐earth (RE) atoms incorporated in lattice greatly tunned the optical, electrical, magnetic, and catalytic performance of doped crystal through the peculiar atomic electron structure of RE. The dimensionality scale‐down of RE oxides can further promote their unique traits and broaden their applications. The UV photodetection performance of (111) oriented CeO₂ thin film is limited by the existence of grain boundaries, defects, and strains. Consequently, single‐crystal 2D CeO₂ is promising for photodetection as it lacks of grain boundaries and defects. However, the synthesis of large‐sized high‐quality 2D CeO₂ with lateral dimensions over 100 µm is challenging. In this work, a 3.9 nm thick CeO₂ single crystal with 120 µm lateral size is synthesized over a sapphire substrate through a salt‐assisted chemical vapor deposition method, in which an intermediate insulating CeAlO₃ layer is formed between the substrate and 2D CeO₂ to enhance the crystal lattice matching and therefore facilitates the large area growth. The photodetector based on 2D CeO₂ exhibits a photo response from 395 to 532 nm, possibly ascribed to a micro‐strain narrowed bandgap induced at the heterointerface. The photoresponsivity reaches 43.6 A W⁻¹ while the detectivity reaches 7.58 × 10¹¹ Jones under the 395 nm laser irradiation. Besides, the sub‐ms switching kinetics is achieved without gating bias, which is significantly improved over other reported RE oxides‐based photodetectors. This work demonstrates the possibility of the synthesis of large‐size high‐quality 2D RE oxides and their strong potential in high‐performance optoelectronic devices.