Preparation and Characterization of CuO based Core-Shell Heterostructure Nanowires for Photodetector Application

Abstract

One dimensional (1D) nanostructured materials having defined band gap offers constraints in the wide-spectrum applications in sensor, photodetection, such as for visible/ultraviolet (UV) light imaging, memory storage or switches applications. However, the high electron-hole recombination rate that occurs in 1D nanostructured materials inhibits the said applications. This recombination can be greatly suppressed by the introduction of a core/shell nanowire structure, resulting enhanced photocurrent. Furthermore, Core/shell nanowires that consist of two components with distinct functionality are ideal building blocks for nanoscale photodetectors since they have large surface-to-volume ratio, stable chemical and physical properties. On this regard, metal oxide one dimensional (1D) nanostructures such as p-type semiconductor CuO to be the potential candidates because of their ideal band gaps(1.2-2.1eV), low costs fabrication of device, high solar absorbance, high carrier concentration, non-toxicity, and simple manufacturing process. It is expected that copper oxide nanowires with n-type semiconductor in a core–shell heterostructure architecture may enhance the photo response of such material . Therefore, it is worthy to investigate that copper oxide nanowires p-type semiconductor in core and another n-type semiconductor over layer forming core-shell heterostructure architecture may enhance the photo response of such material. We report the synthesis of copper oxide (CuO)/CdSe and CuO/CdS core shell heterostructure nanowires by simple process. In order to prepare CuO/CdSe and CuO/CdS core shell heterostructure nanowires, first CuO nanowires have been grown by thermal oxidation on a copper substrate. Over layer CdSe or CdS shell structure has been prepared by CVD on the grown CuO nanowires as templates that forms CuO/CdSe or CuO/CdS core-shell structure. The synthesized CuO/CdSe and CuO/CdS core-shell heterostructure nanowires have been used to fabricate for photodetector measurement. The measured dark current and photocurrent of CuO has been compared with CuO/CdSe and CuO/CdS. Significant enhancement in dark as well as photocurrent of CuO/CdSe and CuO/CdS compared to Cu has been observed. The increase in current could be attributed to enhancement of free electrons in the heterostructure materials. The efficient photocurrent, responsivity, external quantum efficiency derived for the CuO/CdSe and CuO/CdS core-shell heterostructures may be attributed to the effective charge transport that inhibits recombinations of charges. These results suggest great potential of CuO/CdSe and CuO/CdS heterostructures for efficient UV light detection, and, more importantly, signify the advantages of type-II semiconducting heterostructures for construction of high-performance photodetectors.