Interface study of hybrid CuO nanoparticles embedded ZnO nanowires heterojunction synthesized by controlled vapor deposition approach for optoelectronic devices

Abstract

Fabrication of p-CuO/n-ZnO heterojunction through a vapor deposition growth of hybrid CuO nanoparticles embedded ZnO nanowires for enhance optoelectronic device properties has been investigated. The controlled growth of ZnO NWs with reasonably uniform size having an average length of 1.5 µm and an average diameter of 40 nm was achieved using smart thermal CVD without employing any catalyst. Embedding CuO NPs with sputtering and thermal oxidation approach, a good hybridization of CuO over 1D ZnO NWs was achieved. The hybrid structure involved uniform CuO NPs deposition with a size less than 10 nm in diameter on the surface of the ZnO NWs. The performance analysis reveals significantly improved photoluminescence (PL) emission properties with good crystallinity and lesser intrinsic defect properties compared to the pristine ZnO NWs. This was evidently due to good interface interaction between ZnO NWs and CuO NPs to construct p-CuO/n-ZnO heterojunction. The I–V characteristics of the fabricated single hybrid nanowire heterojunction at CuO/ZnO interface, measured in dark by conductive nanoprobe AFM (C-AFM) at ultra-high vacuum, shows a good rectifying behavior with a less significant hysteresis. A remarkably good p-n junction showing a lesser number of charges were trapped at the surface of CuO nanoparticles/ZnO nanowires heterojunction was determined. The fabricated heterojunction at the CuO/ZnO interface indicates comparably small turn-on voltage ~0.7 eV and excellent ideality factor ~1.58 under dark. The band offset of the heterojunction was determined by XPS and was found to be type II band structure. The superior tuning in the optical band gap without any intrinsic defects illustrated its better crystallinity and the formation of p-n heterojunctions at the CuO/ZnO interface can attributed to the good alignment, high aspect ratio, and better crystallinity of hybrid NWs. These results have shown that hybrid CuO Nanoparticles/ZnO Nanowires heterojunction synthesized by vapor deposition has the potential to be used in optoelectronic device and other energy applications.