Raman scattering investigations on Co-doped ZnO epitaxial films: Local vibration modes and defect associated ferromagnetism |
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Institution: | 1. National Key Laboratory of Crystal Materials and School of Physics, Shandong University, Jinan, Shandong 250100, China;2. School of Physics and Engineering, Qufu Normal University, Qufu, Shandong 273165, China;3. Physics Department, University of Hong Kong, Pokfulam Road, Hong Kong, China |
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Abstract: | Raman scattering spectroscopy has been performed on high quality Co-doped ZnO epitaxial films, which were grown on Al2O3 (0001) by oxygen-plasma assisted molecular beam epitaxy. Raman measurements revealed two local vibration modes (LVMs) at 723 and 699 cm−1 due to the substitution of Co2+ in wurtzite ZnO lattice. The LVM at 723 cm−1 is found to be an elemental sensitive vibration mode for Co substitution. The LVM at 699 cm−1 can be attributed to enrichment of Co2+ bound with oxygen vacancy, the cobalt–oxygen vacancy–cobalt complexes, in Zn1−xCoxO films associated with ferromagnetism. The intensity of LVM at 699 cm−1, as well as saturated magnetization, enhanced after the vacuum annealing and depressed after oxygen annealing. |
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Keywords: | Raman scattering Oxide magnetic semiconductor Epitaxial films |
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