Investigation of nonpolar (1 1 2¯ 0) a-plane ZnO films grown under various Zn/O ratios by plasma-assisted molecular beam epitaxy |
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Authors: | Seok Kyu Han Jung-Hyun Kim Soon-Ku Hong Jae-Ho Song Jung-Hoon Song Jae Wook Lee Jeong Yong Lee Sun Ig Hong Takafumi Yao |
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Affiliation: | 1. Department of Advanced Materials Engineering, Chungnam National University, Daejeon 305-764, Republic of Korea;2. Department of Physics, Kongju National University, Gongju 314-701, Republic of Korea;3. Department of Materials Science and Engineering, KAIST, Daejeon 305-701, Republic of Korea;4. Center for Interdisciplinary Research, Tohoku University, Sendai 980-8578, Japan |
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Abstract: | Structural and optical properties of nonpolar a-plane ZnO films grown with different II/VI ratios on r-plane sapphire substrates by plasma-assisted molecular beam epitaxy were investigated. Even by increasing the II/VI ratio across the stoichiometric flux condition a consistent surface morphology of striated stripes along the ZnO 〈0 0 0 1〉 direction without any pit formation was observed, which is contrary to polar c-plane ZnO films. Root mean square surface roughness, full width at half maximum values of X-ray rocking curves, defect densities, and photoluminescence were changed with the II/VI ratio. The sample grown with stoichiometric flux condition showed the lowest value of rms roughness, the smallest threading dislocation and stacking fault densities of ∼4.7×108 cm−2 and ∼9.5×104 cm−1, respectively, and the highest intensity of DoX peak. These results imply that the stoichiometric flux growth condition is suitable to obtain superior structural and optical properties compared to other flux conditions. |
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Keywords: | A3. Molecular beam epitaxy A1. Characterization B1. Oxides B1. Zinc compounds B2. Semiconductiong II&ndash VI materials |
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