以化學溶液法製備氧化鋅微奈米結構之研究

Abstract

氧化鋅是一種很重要的II–VI半導體，其直接能隙為3.37 eV，激子束縛能為60 meV。一般製備氧化鋅奈米結構製程需要複雜的反應或是昂貴的設備；而我們使用的是一種簡單的化學溶液法製程，它只需要在低溫下進行氧化還原反應，就可以很容易的製備出氧化鋅奈米結構。其最終目的為提高氧化鋅結構的表面積，並應用於染料敏化太陽能電池。 本研究使用化學溶液法，在黏貼金屬島的ITO導電玻璃上，自組裝氧化鋅的微奈米結構。本實驗不需在基材上沉積一層氧化鋅晶種層，而是以黏貼金屬島在基材上，提供電子吸引鋅離子在基材上成核，藉由改變還原液濃度、反應溫度、反應時間及添加界面活性劑等參數，控制氧化鋅的形貌與尺寸，並推論出氧化鋅微奈米結構之成長機制。 由實驗結果可得知，氧化鋅的形貌主要為六角棒狀，且醋酸鋅濃度增加與增加PVP添加量，都會使棒狀氧化鋅的長寬比降低；而反應溫度與反應時間增加則會使棒狀氧化鋅的長寬比增加。在醋酸鋅濃度為100 ppm，反應溫度為90℃，反應時間為15小時，可製備出氧化鋅長寬比的最佳參數，長度可成長至9μm且長寬比為18。由TEM分析顯示氧化鋅微奈米柱成長方向為<0001>。在醋酸鋅溶液濃度為100 ppm、反應溫度70oC 、反應6小時，可得到最佳的PL發光性質。在特定參數下，可製備出特殊形貌的氧化鋅，如花狀、星型、薄膜狀、釘子狀與中空六角柱等。

ZnO is an II-VI semiconductor. It has a wide band gap of 3.37 eV and a large exciton binding energy of 60 meV. Generally, the growth of ZnO nanostructures requires complicated reaction and expensive equipments. But in this paper, we use a simple solution chemical method to prepare ZnO nanostructures at low temperatures. And our objective is enhance the surface area of ZnO which makes it available in dye-sensitized solar cells application. In this study , the ZnO nanostructure are fabricated by simple solution chemical method. Differently, we paste the metal-island on the substrate instead of ZnO coated seed surfaces. In this novel method, the metal-island play as electron provider, and were further providing the nucleation sites on ITO surface by electrons transmit between the metal-island and conducting substrates. Varies parameters as solution concentration, working temperature, reaction time and surfactants were help us to construction the growth mechanism of ZnO nanostructure ,and we can control the size and morphology of self-assembled ZnO by adjust those parameters. According to our research, the morphologies of ZnO are usually hexagonal rod. The aspect ratio of ZnO Micro-rod is reduced with an increase of the concentration of zinc acetate solution and added surfactants. However, the aspect ratio of ZnO micro-rod is increased with an increase of the reaction temperature and time. Using 100 ppm zinc acetate solution at 90℃ for 15 hours, we can obtain the largest aspect ratio 18 with a 9 μm length ZnO mirco-rod. TEM analysis reveals that the ZnO nanorod grows along the <0001> direction. The best PL light emission properties were achieved by the reaction in 100ppm Zinc acetate solution at 70℃for 6 h. And we have demonstrated that under the specific condition, the special morphology of ZnO products like flower, star, film, nail and hollow-center hexagonal rod were be successfully fabricated.