Abstract
The fabrication and properties of n-ZnO nanowires/p-CuO coaxial heterojunction (CH) with a photoresist (PR) blocking layer are reported. In our study, c-plane wurtzite ZnO nanowires were grown by aqueous chemical method, and monoclinic CuO (111) was then coated on the ZnO nanowires by electrochemical deposition to form CH. To improve the device performance, a PR layer was inserted between the ZnO buffer layer and the CuO film to serve as a blocking layer to block the leakage current. Structural investigations of the CH indicate that the sample has good crystalline quality. It was found that our refined structure possesses a better rectifying ratio and smaller reverse leakage current. As there is a large on/off ratio between light on and off and the major light response is centered at around 424 nm, the experimental results suggest that the PR-inserted ZnO/CuO CH can be used as a good narrow-band blue light detector.
Highlights
Because of its wide band gap (3.37 eV) and large exciton binding energy (60 meV), zinc oxide (ZnO) is one of the most promising materials for optoelectronic device applications in the ultraviolet (UV) region [1,2,3]
ZnO thin films can be produced by several techniques, such as reactive evaporation, molecular beam epitaxy (MBE) [4,5,6], magnetron sputtering technique [7], pulsed laser deposition (PLD) [8], sol–gel technique [9], chemical vapor deposition, electrochemical deposition [10], and spray pyrolysis [11]
A wide variety of processes, including sputtering method [14], sol–gel technique [17], thermal oxidation [18], and modified hydrothermal method [19], have been developed to fabricate ZnO/CuO CH. These works demonstrated that good rectification ratio and good photoresponse can be obtained with ZnO/CuO coaxial heterojunctions
Summary
Because of its wide band gap (3.37 eV) and large exciton binding energy (60 meV), zinc oxide (ZnO) is one of the most promising materials for optoelectronic device applications in the ultraviolet (UV) region [1,2,3]. ZnO-based heterojunctions have been extensively studied for application as UV photodetectors These ZnO-based heterojunctions can be classified into two categories: thin film heterojunction (FH) and coaxial heterojunction (CH). A wide variety of processes, including sputtering method [14], sol–gel technique [17], thermal oxidation [18], and modified hydrothermal method [19], have been developed to fabricate ZnO/CuO CH. These works demonstrated that good rectification ratio and good photoresponse can be obtained with ZnO/CuO coaxial heterojunctions. With the increase of reverse bias from 1 to 3 V, the responsivity increases from 0.4 to 3.5 A W−1 under a 424-nm light illumination
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