氧化鋅奈米結構之製備及其光電分析與應用

Synthesis and characterization of ZnO nanostructures: optoelectronic analyses and applications

趙家忻(Cha-Hsin Chao)

指導教授 ： 林清富

國立臺灣大學/電機資訊學院/光電工程學研究所/博士(2010年)

https://doi.org/10.6342/NTU.2010.02619

摘要

在本論文中，我們研究了使用水熱法製備之氧化鋅奈米結構的合成，同時也探討了氧化鋅奈米結構的合成機制及其材料和光電特性。材料特性的檢驗由場發射電子顯微以及X-ray繞射，能量散射X射線光譜儀來完成。同時也驗證了氧化鋅奈米陣列在發光二極體上的應用，此項特性可以用於增進發光二極體的出光效率。此論文的內容重點可以分為四個部份：
1. 氧化鋅奈米結構的控制成長
在此部份中，我們研究了氧化鋅奈米結構的控制成長機制，同時也從實驗結果中討論了控制氧化鋅奈米結構成長的機制。結果顯示，使用不同溶液濃度成長出的氧化鋅奈米陣列，成長出的尺寸可從50 nm到300 nm。此外，我們也探討了不同幾何尺寸的基板成長出的氧化鋅奈米結構。若是用模板輔助控制成長，使用不同溶液濃度成長出的氧化鋅奈米陣列，成長出的尺寸可從50 nm到1400 nm。
2. 氧化鋅奈米結構的異質界面成長
在此部份中，我們研究了氧化鋅奈米結構的異質接面長晶，同時也從實驗結果中討論了控制氧化鋅奈米結構成長的機制。結果顯示，使用氮化鎵的基板來成長氧化鋅微奈米結構，可以達到良好的長晶品質。此外，我們也探討了不同幾何尺寸的基板成長出的氧化鋅微奈米結構。若是用模板輔助控制成長，使用不同溶液濃度成長出的氧化鋅奈米陣列，成長出的尺寸可從530 nm到3500 nm。
3. 氧化鋅奈米結構增進發光二極體的出光效率
在此部份中，我們研究了氧化鋅奈米結構對於增進氮化鎵發光二極體出光效率的影響。結果顯示，氮化鎵發光二極體的出光效率隨著表面的氧化鋅奈米陣列的長度影響而呈現週期性的振盪變化。出光效率隨氧化鋅奈米柱長度呈現的振盪變化可以解釋為光線在氧化鋅奈米柱裡來回反射，造成發光二極體的特性改變。
4. 氮化鎵奈米結構增進發光二極體的出光效率
在此部份中，我們研究了氮化鎵奈米結構對於增進氮化鎵發光二極體輸出功率的影響。結果顯示，氮化鎵發光二極體的輸出功率隨著表面的氮化鎵奈米陣列的長度影響而呈現週期性的振盪變化，與前部份的結果類似。此結果可由Bruggemann effective medium approximation 及Fabry-Perot resonance來解釋。

關鍵字

氧化鋅 ； 奈米柱 ； 水熱法 ； 電子束微影術 ； 氮化鎵 ； 發光二極體 ； 出光效率 ； 法布里-伯羅振盪

並列摘要

In this thesis, the synthesis of ZnO nanostructures via hydrothermal method is studied. The systhesis chemistry of various ZnO structures and its material and optoelectronic characterization are reviewed and investigated. Field-emission scanning electron microscope (FESEM), X-ray diffraction (XRD) and energy-dispersive X-ray (EDX) spectroscopy are performed to examine the properties of ZnO. Applications of ZnO nanorod arrays have been demonstrated to enhance the light extraction efficiency of light-emitting diodes (LEDs). The content of the thesis can be mainly divided into four part as follows.
1. Controlled-growth of ZnO nanostructures
The experimental techniques of controlled-growth of ZnO nanostructrures used in this dissertation and the underlying growth mechanisms are described. The effect of growth parameters on the formation of ZnO nanorod arrays is elucidated with detailed analysis from our experimental results. The scale and morphology of ZnO nanorod arrays grown on the sol-gel-derived film are controlled with a wide size range from 50 nm to 300 nm in diameter. With applying a template to limit the growth of ZnO rods, the diameters of ZnO rod arrays grown with various solution concentrations can be controlled in the range from 50 nm up to 1400 nm.
2. Hetero-growth of ZnO nanostructures
The heteroepitaxy of ZnO is accomplished on various substrates by hydrothermal method. The results show that the grown ZnO micro/nanostructures and thin films have a good epitaxial quality on GaN substraets. In addition, the differences in morphologies of ZnO rod arrays grown with various diameters of polymer apertures are discussed. The controlled diameters of rods with various solution concentrations and geometry of template are in the range from 530 nm up to 3.5 μm.
3. Enhanced light extractions efficiency of LEDs by ZnO nanorods
The effect of the ZnO rod length on the output light intensity of GaN-based LEDs is investigated. It is firstly found that the EL intensity of GaN-based with ZnO nanorod arrays is varied periodically with the rod length. The oscillation as a function of rod length can be explained as the interference of light emission between interfaces of nanorods, resulting in a modulation of light extraction efficiency of the devices.
4. Enhanced light extractions efficiency of LEDs by GaN nanorods
In addition, the effect of the geometry of GaN rod arrays on the output power of GaN LEDs is studied. It is found that the output power of GaN LEDs with GaN rod arrays is varied with the length and density of rods, which is analogous to the previous results. The Bruggemann effective medium approximation and the Fabry-Perot resonance also work well for GaN rod arrays on GaN LEDs.

並列關鍵字

ZnO ； nanorod ； hydrothermal method ； e-beam lithography ； GaN ； light-emitting diodes ； light extraction efficienty ； Fabry-Perot resonance

參考文獻

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