Influence of reducing anneal on the ferromagnetism in single crystalline Co-doped ZnO thin films
Lu Zhong-Lin(路忠林)a)b)†, Zou Wen-Qin(邹文琴)c), Xu Ming-Xiang (徐明祥)a), and Zhang Feng-Ming(张凤鸣)c)
a Department of Physics, Southeast University, Nanjing 210096, China; b Physics Department and Institute of Innovations and Advanced Studies (IIAS), National Cheng Kung University, Tainan 701, China; c Jiangsu Provincial Laboratory for Nanotechnology, National Laboratory of Solid State Microstructure, and Department of Physics, Nanjing University, Nanjing 210093, China
Abstract This paper reports that the high-quality Co-doped ZnO single crystalline films have been grown on -plane sapphire substrates by using molecular-beam epitaxy. The as-grown films show high resistivity and non-ferromagnetism at room temperature, while they become good conductive and ferromagnetic after annealing in the reducing atmosphere either in the presence or absence of Zn vapour. The x-ray absorption studies indicate that all Co ions in these samples actually substituted into the ZnO lattice without formatting any detectable secondary phase. Compared with weak ferromagnetism (0.16 /Co in the ZnCoO single crystalline film with reducing annealing in the absence of Zn vapour, the films annealed in the reducing atmosphere with Zn vapour are found to have much stronger ferromagnetism (0.65 /Co at room temperature. This experimental studies clearly indicate that Zn interstitials are more effective than oxygen vacancies to activate the high-temperature ferromagnetism in Co-doped ZnO films, and the corresponding ferromagnetic mechanism is discussed.
Fund: Project partially supported by
National Science Foundation of China (Grant No.~10804017), National
Science Foundation of Jiangsu Province of China (Grant
No.~BK2007118), Research Fund for the Doctoral Program of Higher
Education of China (Grant No.~20070286037), Cyanine-Project
Foundation of Jiangsu Province of China (Grant No.~1107020060),
Foundation for Climax Talents Plan in Six-Big Fields of Jiangsu
Province of China (Grant No.~1107020070) and New Century Excellent
Talents in University (NCET-05-0452).
Cite this article:
Lu Zhong-Lin(路忠林), Zou Wen-Qin(邹文琴), Xu Ming-Xiang (徐明祥), and Zhang Feng-Ming(张凤鸣) Influence of reducing anneal on the ferromagnetism in single crystalline Co-doped ZnO thin films 2010 Chin. Phys. B 19 056101
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