CuO‐Based Photodiodes With Enhanced Performance via Mo Nanosheet Thickness Optimization

Herein, copper oxide (CuO) thin films were deposited onto n‐Si substrates and subsequently coated with Mo nanosheets of controlled thicknesses in the range of 20–300 nm to enhance their photodetection characteristics. The incorporation of Mo nanosheets induced a marked improvement in the crystallinity of the initially amorphous CuO, yielding a well‐defined monoclinic phase and substantially suppressing structural disorder, microstrain, and stacking‐fault density across all thicknesses. The CuO/Mo architecture on Si also underwent significant microstructural refinement, where Mo nanosheets promoted grain enlargement and reduced porosity, resulting in a more compact and electronically favorable film morphology. Mo nanosheets highly engineered the optical properties mainly by reducing the transmittance and reflectance and increasing the light absorption. As planar photodiodes, the devices exhibited a pronounced thickness‐dependent enhancement, with optimal performance achieved near 200 nm of Mo. At this condition, the responsivity increased to 0.8 A/W, the external quantum efficiency exceeded 100%, and the linear dynamic range expanded to ~ 18 dB. Simultaneously, the noise‐equivalent power decreased to 1.7 × 10 −11 W·Hz −1 / 2 , yielding a specific detectivity of ~ 1 × 10 10 Jones, representing a substantial improvement over undoped CuO counterparts. These results demonstrate that controlled Mo‐nanosheet thickness modulation provides an effective and scalable strategy for achieving high‐performance CuO‐based photodiodes.