- 學位論文
奈米結構透明導電氧化材料之應用
Applications of Nanostructural Transparent Conductive Oxides
摘要
本研究以奈米結構透明導電氧化材料為主軸，探討奈米尺度的材料特性，比較結構化之電性及光性表現，並討論應用於透明導電元件之可行性。 本研究分別探討表面織構化薄膜及水熱法摻雜銀奈米柱之優化條件。第一部份是利用噴槍噴霧法製備高表面織構化二氧化錫薄膜，利用微型噴霧器將二氧化錫奈米顆粒均勻噴灑於玻璃基板上，再以常壓化學氣相沉積法(APCVD)將二氧化錫薄膜鍍製於基板上，此方法可以簡單製程和低成本的方式大量製備。隨著噴灑的奈米顆粒濃度增加，薄膜表面的粗糙度也會大幅增加，但所增加的表面會造成穿透度的損失，故本實驗最佳化條件在平均穿透度80.6 %時，可達到35.0 %的霧度(haze)。二氧化錫薄膜沉積於奈米顆粒的生長機制也於文中討論，二氧化錫薄膜對於結晶奈米顆粒的同質成長和非晶玻璃基板的異質成長，是造成表面生成球狀起伏的最大原因，以此方法製備的表面織構化二氧化錫薄膜將可應用於薄膜太陽電池。 第二部分是研究水熱法氧化鋅奈米柱於不同pH值環境下的生長機制，利用表面形貌估算奈米柱之表面能，再以經驗式得出表面形貌與pH值的關係式。透過螢光光譜儀可以得出奈米柱的缺陷密度，文中也探討缺陷密度與水熱法環境的關係，當中發現在pH=8.94時，會出現形貌及缺陷密度大幅改變的轉換點(transition point)，以此轉換點可將奈米柱之形貌歸類成兩種：當pH小於此點時，奈米柱會傾向成長a軸方向，形成直徑較寬的六角柱體；當pH大於此點時，奈米柱會沿著[0001]方向快速沉積，形成長度較長的圓柱體。在摻雜銀原子的水熱法研究中，我們發現此轉換點環境最有利於銀原子的摻雜，此原因與鋅離子於溶液中的最大溶解度有關。在熱蒸鍍銀電極與氧化鋅奈米柱形成蕭特基接面(Schottky contact)的研究中，摻雜銀之氧化鋅奈米柱能有效增加整流比例，其最佳化條件為10%的摻雜銀之氧化鋅奈米柱，可達到10的4次方的整流比，此結果顯示出水熱法製備摻雜銀之氧化鋅奈米柱可應用於整流元件。
並列摘要
Highly-textured surface SnO2 transparent conductive oxide thin films were directly deposited using the atmospheric pressure chemical vapor deposition technique on nanoparticle-coated glass substrates. A simple nozzle-spraying process was developed for the SnO2 nanoparticle coating of highly-textured SnO2 thin films. The nozzle-spraying process caused the surface morphology of the SnO2 films to change from a pyramidal shape to a flower-like double texture. Optimum nanoparticle-coated SnO2 thin films had a haze value of 35.0±4.0 % and an average visible optical transmittance of 80.6±2.2 % in the wavelength range of 400 to 900 nm. The morphological evolution of the SnO2 thin films was apparent on the hetero-surface of the amorphous glass and multicrystalline SnO2 nanoparticles. These results indicate that the crystalline SnO2 nanoparticle has an important role in the fabrication of a flower-like double texture, and that the texture of these SnO2 thin films offer a promising transparent conductive material for thin film solar cells. ZnO nanorods were fabricated by a hydrothermal process at various pH values. The growth mechanisms for these nanorods were studied by investigating defect density, surface energy, and point of zero charge. An empirical formula was developed for the prediction of ZnO nanorod morphology with time and pH value as variables. The defect ratio determined by photoluminescence indicated that the defect density with growth solutions having pH values was lower than the transition point, while the defect density is relatively high when pH is higher than the transition point. Studies of Ag-doped ZnO nanorods report the possibility that the effectiveness of the Ag doping correlates with the pH value. In our study, the optimum doping amount was found to occur when the pH value was located at the transition point, which implies that conditions with the lowest zinc solubility may result in the most effective Ag doping. A Schottky diode was prepared by depositing Ag metal contacts on the Ag-doped ZnO nanorods. The optimum rectification ratio was found in 10% of Ag-doped ZnO rods.
參考文獻
延伸閱讀
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