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Investigations of the valence states, cobalt ion distribution, and defect structures in Co-doped ITO films

Published online by Cambridge University Press:  21 June 2018

Zhen Lin ,
Wenlong Lai ,
Zhonghua Wu ,
Jiwen Liu  and
Yukai An
Zhen Lin
Affiliation:
School of Material Science and Engineering, Tianjin University of Technology, Tianjin 300384, China
Wenlong Lai
Affiliation:
School of Material Science and Engineering, Tianjin University of Technology, Tianjin 300384, China
Zhonghua Wu
Affiliation:
Beijing Synchrotron Radiation Facility (BSRF), Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 1040049, China
Jiwen Liu
Affiliation:
Key Laboratory of Display Materials and Photoelectric Devices, Ministry of Education, Tianjin Key Laboratory for Photoelectric Materials and Devices, National Demonstration Center for Experimental Function Materials Education, School of Material Science and Engineering, Tianjin University of Technology, Tianjin 300384, China
Yukai An*
Affiliation:
Key Laboratory of Display Materials and Photoelectric Devices, Ministry of Education, Tianjin Key Laboratory for Photoelectric Materials and Devices, National Demonstration Center for Experimental Function Materials Education, School of Material Science and Engineering, Tianjin University of Technology, Tianjin 300384, China
*
a)Address all correspondence to this author. e-mail: ayk_bj@126.com
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Abstract

The valence states, the distribution of Co ions, and defect structures in the Co-doped ITO films with Co concentrations of 5–13 at.% were examined by X-ray absorption spectroscopy (XAS) at Co, K, and L-edges. The structural analyses and ab initio calculations reveal that the Co atoms are substantially incorporated into the ITO lattice and form cobalt–vacancy complexes, while partial formation of Co0 species is observed for all the films. The analyses of Co–K edge XAS reveal that the Co–O bond length RCo–O is shortened and the corresponding Debye–Waller factor (σ2) obviously increases with Co doping, implying the relaxation of oxygen environment around the substitutional Co ions. The qualitative fitting of Co L3-edge XAS further confirms the coexistence of Co0 and Co2+ in the films. The Co atoms mainly occupy the substitutional sites of In2O3 lattices with the metallic Co clusters being about 20–43 at.% for the 5, 7, and 8.5 at.% Co-doped ITO films. However, a significant fraction (∼57 at.%) of metallic Co clusters is found in the 13 at.% Co-doped ITO film.

Keywords

ITO filmCo dopinglocal structureCo clusters
Type
Article
Information
Journal of Materials Research , Volume 33 , Issue 16 , 28 August 2018 , pp. 2336 - 2341
Copyright
Copyright © Materials Research Society 2018 

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