Room‐Temperature Interfacial Reactive‐Template Epitaxy of NiO/4H‐SiC for Dual‐Mode UV Photodetection

ABSTRACT Room‐temperature epitaxial growth of functional oxides on wide‐bandgap semiconductors is critical for heterogeneous integration and functional diversification, yet remains largely unachieved due to insufficient atomic mobility and severe lattice/chemical mismatch. Here, we introduce a reactive‐template‐induced strategy (RTIS) that enables atomically precise NiO/4H‐SiC heterostructures via room‐temperature pulsed laser deposition (PLD). Face‐selective epitaxy on Si‐terminated versus C‐terminated surfaces confirms a chemical−template mechanism mediated by Si−O−Ni bonding. The undoped NiO films exhibit exceptional crystallinity with crystal tilting of only 82 arcseconds and atomically sharp interfaces. Li‐doping preserves the epitaxial quality, enabling dual‐mode ultraviolet (UV) photodetectors based on oxide/semiconductor heterostructures with both solid‐state and photoelectrochemical (PEC) operation. The solid‐state device demonstrates impressive performance with a responsivity of 2.09 A W −1 and detectivity of 1.09 × 10 14 Jones under 254 nm illumination. The PEC‐mode device achieves a responsivity of 159 mA W −1 , sub‐millisecond response times, and remarkable longterm operational stability even in natural seawater. First‐principles calculations reveal fundamentally distinct interfacial electronic structures at NiO/metal versus NiO/liquid junctions, elucidating the underlying mechanisms responsible for their contrasting operational behaviors. RTIS extends to multiple wide‐bandgap platforms (GaN, AlGaN, ε‐Ga 2 O 3 , 3C‐SiC), establishing a versatile pathway for oxide/WBG integration with implications for advanced optoelectronic and (photo)electrocatalytic systems.