Characteristics of Carrier Transport and Crystallographic Orientation Distribution of Transparent Conductive Al-Doped ZnO Polycrystalline Films Deposited by Radio-Frequency, Direct-Current, and Radio-Frequency-Superimposed Direct-Current Magnetron Sputtering

Junichi Nomoto; Katsuhiko Inaba; Shintaro Kobayashi; Takeshi Watanabe; Hisao Makino; Tetsuya Yamamoto

doi:10.3390/ma10080916

Characteristics of Carrier Transport and Crystallographic Orientation Distribution of Transparent Conductive Al-Doped ZnO Polycrystalline Films Deposited by Radio-Frequency, Direct-Current, and Radio-Frequency-Superimposed Direct-Current Magnetron Sputtering

Materials (Basel). 2017 Aug 9;10(8):916. doi: 10.3390/ma10080916.

Authors

Junichi Nomoto¹, Katsuhiko Inaba², Shintaro Kobayashi³, Takeshi Watanabe⁴, Hisao Makino⁵, Tetsuya Yamamoto⁶

Affiliations

¹ Research Institute, Kochi University of Technology, Kochi 782-8502, Japan. nomoto.junichi@kochi-tech.ac.jp.
² X-Ray Research Laboratory, Rigaku Corporation, Tokyo 196-8666, Japan. inaba@rigaku.co.jp.
³ X-Ray Research Laboratory, Rigaku Corporation, Tokyo 196-8666, Japan. s-kobaya@rigaku.co.jp.
⁴ Japan Synchrotron Radiation Research Institute (JASRI), SPring-8, Hyogo 679-5198, Japan. t5511001@spring8.or.jp.
⁵ Research Institute, Kochi University of Technology, Kochi 782-8502, Japan. makino.hisao@kochi-tech.ac.jp.
⁶ Research Institute, Kochi University of Technology, Kochi 782-8502, Japan. yamamoto.tetsuya@kochi-tech.ac.jp.

Abstract

We investigated the characteristics of carrier transport and crystallographic orientation distribution in 500-nm-thick Al-doped ZnO (AZO) polycrystalline films to achieve high-Hall-mobility AZO films. The AZO films were deposited on glass substrates at 200 °C by direct-current, radio-frequency, or radio-frequency-superimposed direct-current magnetron sputtering at various power ratios. We used sintered AZO targets with an Al₂O₃ content of 2.0 wt. %. The analysis of the data obtained by X-ray diffraction, Hall-effect, and optical measurements of AZO films at various power ratios showed that the complex orientation texture depending on the growth process enhanced the contribution of grain boundary scattering to carrier transport and of carrier sinks on net carrier concentration, resulting in the reduction in the Hall mobility of polycrystalline AZO films.

Keywords: Al-doped ZnO; X-ray diffraction; carrier transport; crystallographic orientation; initial growth stage; magnetron sputtering; transparent conducting oxide.