Microstructure, optical, electrical, and magnetic properties of ZnO/CuO thin films prepared using two-stage magnetron sp
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Microstructure, optical, electrical, and magnetic properties of ZnO/ CuO thin films prepared using two-stage magnetron sputtering and diffusion doping process Tai‑Hsiang Liu1 · Fei‑Yi Hung1,2 · Cheng‑Hung Chen1,2 · Kuan‑Jen Chen1,2 Received: 17 November 2019 / Revised: 16 January 2020 / Accepted: 20 January 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract In this study, CuZnO (CZO) films were fabricated by two-stage magnetron sputtering. The film crystallization and the diffusion of the copper layer were enhanced by 1 h heat treatment (500 ℃); then the nanowire was grown from the CZO film system using an aqueous solution method. After 2 h of heat treatment (500 ℃), the film and the nanowire system were observed. The morphology and microstructure were analyzed and their optical and electromagnetic properties were analyzed. The CZO thin film is doped with copper atoms by zinc oxide so that the concentration of the carrier is increased and the ferromagnetism is enhanced and the electrical properties are improved. There are many oxygen vacancies and interstitial zinc on the nanowire, which increases the concentration of zinc oxide carriers. The carriers improve electrical and magnetic properties. After heat treatment, copper atoms were diffused into the ZnO film layer in ZnO/CuZnO system, which can greatly improve the electrical and magnetic properties of the structure.
1 Introduction Metal oxides of nonmaterial such as ZnO [1], CuO [2, 3], nO2 [4], In2O3 [5], and TiO2 [6] have good optical and elecS tromagnetic properties. These were widely used in different optoelectronic component applications such as photocatalyst [7], solar cell [8], photodiode [9], and sensor [10]. Zinc oxide is a conventional n-type semiconductor oxide with a wide direct energy gap (about 3.37 eV at room temperature); copper oxide is a p-type transition metal oxide, which is an indirect energy gap (~ 1.2 eV). In addition, some atom (Cu, Ag, C, Al, etc.) were chosen for dopant to improve the electrical and magnetic properties for reason that pure ZnO film has intrinsic defect problem. Zinc oxide is also a diluted magnetic semiconductor, which can enhance its magnetic properties through the doping of copper atoms [11]. And Cu has higher diffusion coefficient than most other dopping atom. Therefore, copper was chosen for this study. It is * Fei‑Yi Hung [email protected] 1
Department of Materials Science and Engineering, National Cheng Kung University, Tainan 701, Taiwan
The Instrument Center, National Cheng Kung University, Tainan 701, Taiwan
2
different from the doping method of past research [12, 13]. In this study, the Cu/ZnO two-time sputtering method was used, and the nanowires were grown by low-temperature hydrothermal method. Owing to the feature of high diffusion mobility of Cu, it could easily diffuse into ZnO film by simple heat treatment. The manufacture process becomes much easier and cost less than traditional implantation methods.
2 Experimental procedure The film was prepare
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