利用脈衝雷射沉積法製備氧化鋅薄膜及特性研究

Growth and Characterization of ZnO Thin Films by Pulsed Laser Deposition

吳慶泰(Q.T. Wu)

指導教授 ： 洪魏寬

國立臺北科技大學/機電學院/光電工程系所/碩士(2006年)

https://doi.org/10.6841/NTUT.2006.00098

摘要

本研究以脈衝雷射沉積法於c面藍寶石基板上成長氧化鋅(ZnO)薄膜，有系統地探討生長參數對薄膜表面形貌、粗糙度、結晶度、及光學特性的影響。所使用的光源為Nd：YAG Q-switched雷射，其波長為266 nm、脈衝寬度小於10 ns、重覆頻率10 Hz；使用的靶材為純度99.9％的氧化鋅。我們發現雷射的能量密度及聚焦在靶上的雷射光點面積大小，對於ZnO膜的厚度和磊晶有很大的影響。樣品的結構與光學性質與基板溫度、氣體壓力、生長時間、和靶材與基板間的距離皆有很強的相關性。電子顯微鏡及原子力顯微鏡測量顯示，在基板溫度約650oC、氧壓約0.01 Torr、靶-基板距離4.5 cm時所成長的ZnO薄膜，其表面粗糙度僅約為0.8 nm。此樣品的光激螢光譜亦顯示較強的紫外光峰與較弱的綠光帶，表示其氧空缺相關的缺陷較少。有趣的是，我們亦發現密集排列的直立ZnO奈米線(線徑約25 nm)可在適當的條件下形成，其發光光譜與薄膜相較，顯示更高的紫外光對可見光之強度比值。

關鍵字

脈衝雷射沉積 ； 氧化鋅

並列摘要

In this study, ZnO thin films were grown on c-plane sapphire substrates by pulsed laser deposition. The effects of the growth parameters on the film morphology, roughness, crystallinity, and optical properties were systematically investigated. An Nd:YAG Q-switched laser operating at a wavelength of 266 nm, a pulse duration less than 10 ns, and a repetition rate of 10 Hz, was used to ablate a ZnO target of 99.9% purity. The ablation laser fluence and the beam spot area were found to have very strong effects on the thickness and the epitaxy of the ZnO films. The structural and optical properties of the as-grown samples were correlated with the substrate temperature, ambient pressure, growth time,, and the distance between target and substrate. As revealed from the measurements of scanning electron microscopy and atomic force microscopy, the ZnO film grown at the optimal condition (substrate temperature ~650oC, oxygen pressure ~ 0.01 Torr, target-substrate distance ~ 4.5 cm) has a very smooth surface with roughness ~ 0.8 nm. The photoluminescence spectrum of this sample shows a strong ultraviolet peak and a weak green band, indicating rather low concentration of structural defects. More interestingly, we observed that high-density well-aligned ZnO nanowires (diameter ~ 25 nm) can form on the substrate under suitable growth conditions. The emission spectrum of such nanowires exhibits a higher ratio of ultraviolet to visible (deep-level) emission intensities, as compared with the film structure.

並列關鍵字

pulsed laser deposition ； ZnO

參考文獻

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