Effects of Deposition Temperature and Hydrogen Plasma on the Properties of the Radio-Frequency Magnetron Sputtering Depo
A 98 mol % ZnO–1 mol % Al2O3 (AZO) compound was sintered at 1,350 °C as a target and deposited on glass substrates using a radio-frequency magnetron (r.f.) sputtering system, under the 30 sccm 98 % Ar + 2 % H2 ambient. The effect of deposition temperature
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Abstract A 98 mol % ZnO–1 mol % Al2O3 (AZO) compound was sintered at 1,350 C as a target and deposited on glass substrates using a radio-frequency magnetron (r.f.) sputtering system, under the 30 sccm 98 % Ar + 2 % H2 ambient. The effect of deposition temperature (25–300 C) on carrier concentration, carrier mobility, resistivity, and optical transmission spectrum of the AZO films was studied. The Burstein-Moss shift was observed and used to prove that defects in the AZO films decreased with increasing deposition temperature. The effect of hydrogen (H2) plasma on carrier concentration, carrier mobility, resistivity, and optical transmission spectrum of the different temperature-deposited AZO films was also studied. The value variations in the optical band gap (Eg value) of the AZO films were evaluated from the plots of I ¼ I0eαt, where α2 ¼ hν Eg. The measured Eg value of the as-deposited AZO films increased with increasing deposition temperature and had no apparent trend difference as the H2 plasma was used. Keywords AZO films • Deposition temperature • Hydrogen (H2) plasma
F.-H. Wang • C.-C. Huang Department of Electrical Engineering, National Chung Hsing University, Taichung, Taiwan, R.O.C. C.-C. Diao • C.-C. Wu Department of Electronic Engineering, Kao Yuan University, Kaohsiung, Taiwan, R.O.C. C.-F. Yang (*) Department of Chemical and Materials Engineering, National University of Kaohsiung, Kaohsiung, Taiwan, R.O.C. e-mail: [email protected] J. Juang and Y.-C. Huang (eds.), Intelligent Technologies and Engineering Systems, Lecture Notes in Electrical Engineering 234, DOI 10.1007/978-1-4614-6747-2_90, # Springer Science+Business Media New York 2013
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1 Introduction TCO films are also the key components in flat panel displays and thin-film solar cells [1]. In the past, the indium tin oxide (ITO) was the most extensively used material because the ITO films yielded excellent electrical properties and optical transmittance characteristics in the visible region. The ever-increasing demand was caused by the large growth of flat panel displays and solar cell market, causing the price of ITO to rise quickly over the past years. This has caused the increased efforts to improve material properties and production processes for other TCO materials. Therefore, the Al-doped ZnO (AZO) films have been extensively studied in recent years because they combine attractive properties with high visible transparency and electrical conductivity [2]. Hydrogen (H2) plays a very important role in many semiconductors and is an indispensable ingredient in integrated circuit fabrication, because it passivates the defects at the Si/SiO2 interfaces [3]. Besides, H2 also forms a strong bond with oxygen (O2) and provides a powerful driving force for its incorporation in the crystallization of ZnO [4]. This incorporation is accompanied by remarkably large relaxations of the surrounding atoms. H2 never forms an electrically neutral impurity inside a semiconductor or insulator [5]. It can either invariably give
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