Influences of ZnO buffer layers on the quality of ZnO films synthesized by the metal-organic chemical vapor deposition process |
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Authors: | Sun-Hong Park Chul-Hwan Choi Kyoung-Bo Kim Seon-Hyo Kim |
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Affiliation: | (1) Department of Environmental Science and Engineering, Pohang University Science and Technology, 790-784 Pohang, Korea;(2) Department of Materials Science and Engineering, Pohang University Science and Technology, Korea;(3) R&D Center, NINEX, Kyongki-Do, 459-040, Korea |
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Abstract: | High-quality ZnO thin films were prepared by metal-organic chemical vapor deposition (MOCVD) on a sapphire (a-Al2O3) substrate. The synthesis of ZnO films was performed over a substrate temperature of 400–700°C and at chamber pressures of
0.1–10 torr. The structural and optical properties of ZnO films were investigated in terms of deposition conditions, such
as substrate temperature, working pressure, and the ratio of Zn precursor (Diethylzinc (DEZn)) to oxygen. The ZnO films, preferentially
oriented to 34.42° diffraction because of the (002) plane, were obtained under processing conditions of 700°C and 3 torr.
This film shows a full-width at half-maximum (FWHM) of 0.4–0.6°. The results of photoluminescence (PL) spectroscopy also show
a strong near band-edge emission at 3.36 eV at 10 K as well as a very weak emission at deep levels around 2.5 eV at room temperature.
In addition, we are interested in the introduction of ZnO buffer-layer growth by the sputtering process to reduce lattice
mismatch stress. This paper addresses how to advance the crystalline and optical properties of film. The ZnO film grown with
the aid of a buffer layer shows a FWHM of 0.06–0.1° in the x-ray diffraction (XRD) pattern. This result indicates that crystalline
properties were highly improved by the ZnO buffer layers. The PL spectroscopy data of ZnO film also shows a strong near band-edge
emission and very weak deep-level emission similar to films synthesized without a buffer layer. Accordingly, synthesized ZnO
films with buffer layers indicate fairly good optical properties and low defect density as well as excellent crystallinity. |
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Keywords: | Metal organic chemical vapor deposition (MOCVD) sputtering buffer layer |
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