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Preparation of CuAlO2 Thin Films by Radio Frequency Magnetron Sputtering and the Effect of Sputtering on the Target Surface
T. Ehara1,2, R. Iizaka1, M. Abe1, K. Abe1, T. Sato1
1 Faculty of Science and Engineering, Ishinomaki Senshu University, 1 Shinmito, Minamisakai, Ishinomaki, 986 – 8580, Japan,
2 Faculty of Human Studies, Ishinomaki Senshu University, 1 Shinmito, Minamisakai, Ishinomaki, 986 – 8580 Japan.
received September 5, 2016, received in revised form October 26, 2016, accepted December 9, 2016
Vol. 8, No. 1, Pages 7-12 DOI: 10.4416/JCST2016-00066
Abstract
Powder, a sputtering target, and thin films of CuAlO2 have been prepared by means of radio frequency (rf) magnetron sputtering and characterized. CuAlO2 powder has been synthesized from a stoichiometric mixture of Cu2O and Al2O3 powders by means of heat treatment at 1100 °C in N2 for 40 h. Initially, a mixture of 3R-CuAlO2 (rhombohedral) and 2H-CuAlO2 (hexagonal) was obtained after the heat treatment for 30 h, then, 3R-CuAlO2-dominant powder was obtained after further heat treatment as a result of the phase transformation reaction from 2H-CuAlO2 to 3R-CuAlO2. A CuAlO2 sputtering target has been prepared by pressing the 3R-CuAlO2 powder into a target form at room temperature. We have confirmed the target can be used in film preparation by means of rf magnetron sputtering. However, after film deposition, the target surface partially causes phase transformation from 3R-CuAlO2 to 2H-CuAlO2 owing to the effect of sputtering. Thin films prepared by means of sputtering of the target by oxygen plasma followed by thermal annealing in N2 at a temperature higher than 800 °C for 10 h become CuAlO2 thin films. The film annealed at 800 °C exhibits an optical bandgap of 3.51 eV and resistivity of 1.2×103; Ωcm.
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Keywords
Transparent conductive oxide, sputtering, ceramic thin films, phase transformation reaction, properties
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