Effects of Growth Parameters on Surface-morphological, Structural, Electrical and Optical Properties of AZO Films by RF
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Effects of Growth Parameters on Surface-morphological, Structural, Electrical and Optical Properties of AZO Films by RF Magnetron Sputtering Shou-Yi Kuo1,2, Wei-Ting Lin1,3, Liann-Be Chang1,2, Ming-Jer Jeng1,2 Yong-Tian Lu4 and Sung-Cheng Hu4 1 Department of Electronic Engineering, Chang Gung University, Taiwan 2 Green Technology Research Center, Chang Gung University, Taiwan 259 Wen-Hwa 1st Road, Kweishan, Taoyuan 333, Taiwan 3 Department of Optics and Photonics, National Central University, Taiwan 4 Chemical Systems Research Division, Chung-Sung institute of Science & Technology, Taiwan ABSTRACT 500 nm-thick aluminum-doped zinc oxide (ZnO:Al) thin film is usually used as a front transparent conductive oxide (TCO) contact on photovoltaic devices, and for this application is often deposited by a reactive radio-frequency (r.f.) magnetron sputtering system from a ceramic target. This work reports on the preparation and characterization of AZO thin films on Corning 1737 glass substrates grown by reactive r.f.-magnetron sputtering from a ZnO ceramic target with 2 wt% Al content. It was found that the growth parameters, such as chamber pressure, working power, and deposition temperature, have significant influences on the properties of AZO films. According to the experimental results: (1) Films were polycrystalline showing a strong preferred c-axis orientation. (2) With increasing working power, the resistivity decreased, and mobility and the carrier concentration increased. (3) Lower deposition temperature leads to a decrease in resistivity, with 2.5×10-4 Ω-cm representing the lowest resistivity reached.
INTRODUCTION Transparent conductive oxide (TCO) is an important window contact layer of thin solar cells with low electrical resistivity and high optical transmission [1]. Aluminum-doped zinc oxide (ZnO:Al, AZO) thin films are usually studied on photovoltaic devices because they have a number of advantages, such as non-toxicity, low cost, material abundance, relatively low deposition temperature, good anti-reflection, and high thermal/chemical stability in hydrogen plasma treatment [2-4]. AZO films have been prepared by various deposition techniques, such as sputtering, pulsed laser deposition, chemical vapor deposition, spray pyrolysis, and metalorganic chemical deposition [5-9]. Among these techniques, magnetron sputtering technique has became the potential one because of its advantageous features such as simple apparatus, high deposition rates, and low deposition temperature [10]. In this work, high quality AZO thin films were fabricated and studied as a function of parameters: growth temperature and working power using Al-doped ZnO (2 wt%) ceramic target. The influences of interstitial Zn and Al2O3 containments on structural and optoelectronic properties were discussed.
EXPERIMENT ZnO:Al thin films were deposited on Corning glass (1737, 2×2 cm2) substrates with a standard thickness of 500 nm by radio frequency magnetron sputtering system using high purity ZnO ceramic target with 2 wt% Al (6-inch diam
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