Jun ZOU
,
Shengming ZHOU
,
Xia ZHANG
,
Fenglian SU
,
Xiaomin LI
,
Jun XU
材料科学技术（英）
ZnO thin films were deposited on the substrates of (100) γ-LiAlO2 at 400, 550 and 700℃ using pulsed laser deposition (PLD) with the fixed oxygen pressure of 20 Pa, respectively. When the substrate temperature is 400℃, the grain size of the film is less than 1~$\mu$m observed by Leitz microscope and measured by X-ray diffraction (XRD). As the substrate temperature increases to 550℃, highly-preferred c-orientation and high-quality ZnO film can be attained. While the substratetemperature rises to 700℃, more defects appears on the surface of film and the ZnO films become polycrystalline again possibly because more Li of the substrate diffused into the ZnO film at high substrate temperature. The photoluminescence (PL) spectra of ZnO films at room temperature show the blue emission peaks centered at 430~nm. We suggest that the blue emission corresponds to the electron transition from the level of interstitial Zn to the valence band. Meanwhile, the films grown on γ-LiAlO2 (LAO) exhibit green emission centered at 540 nm, which seemed to be ascribed to excess zinc and/or oxygen vacancy in the ZnO films caused by diffusion of Li from the substrates into the films during the deposition.
关键词:
γ-LiAlO2
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Jun ZOU
材料科学技术（英）
Large-sized (~2 inch, 50.8 mm) γ-LiAlO2 single crystal has been grown by conventional Czochralski (Cz) method, but the crystal has a milky, dendriform center. The samples taken from transparent and milky parts were ground and examined by X-ray diffraction. All diffraction peaks could be indexed in γ-LiAlO2. The crystal quality was characterized by X-ray rocking curve. The full-width at half-maximum (FWHM) values are 116.9 and 132.0~arcsec for transparent and milky parts, respectively. The vapor transport equilibrium (VTE) technique was introduced to modify the crystal quality. After 1000℃/48 h, 1100℃/48 h, 1200℃/48 h VTE processes, the FWHM values dropped to 44.2 and 55.2 arcsec for transparent and milky part, respectively. The optical transmission of transparent part was greatly enhanced from 85% to 90%, and transmission of milky part from 75% to 80% in the range of 190~1900 nm at room temperature. When the VTE temperature was raised to 1300℃, the sample cracked and FWHM values of transparent and milky parts were increased to 55.2 and 80.9 arcsec, respectively. By combining Cz technique with VTE technique, large-sized and high quality γ-LiAlO2 crystal can be obtained.
关键词:
γ-LiAlO2 crystal
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Jun ZOU
,
Shengming ZHOU
材料科学技术（英）
About Φ45 mm LiAlO2 single crystal was grown by Czochralski (Cz) technique. However, the full-width at half-maximum (FWHM) value was high to 116.9 arcsec. After three vapor transport equilibration (VTE) processes, we can obtain high-quality LiAlO2 slice with the FWHM value of 44.2 arcsec. ZnO films were fabricated on as-grown slices and after-VTE ones by pulsed laser deposition (PLD). It was found that ZnO films on the two slices have similar crystallinity, optical transmittance and optical band gap at room temperature. These results not only show that LAO substrate is suitable for ZnO growth, but also prove that the crystal quality of LAO substrate slightly affects the structural and optical properties of ZnO film.
关键词:
Crystal structure
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