氧化鋅奈米結構的特性研究及其在奈米發電機與感測應用

近年來氧化鋅(ZnO)半導體材料已經廣泛地應用於光電領域，由於氧化鋅的直接能隙帶(3.37 eV)以及很大的激子束縛能(60 meV)，使得近幾年開發應用於發光顯示器及光檢測器方面的研究。氧化鋅其六方晶系具有對稱之纖鋅礦結構(wurtzite)所形成的奈米結構有奈米線和奈米帶，目前已知奈米結構種類相當多例如：奈米球(nanocages)、奈米梳(nanocombs)、奈米環(nanorings)、奈米彈簧(nanosprings)、奈米弓 (nanobows) 和奈米盤 (nanodisks)等等。本實驗藉由摻雜不同濃度的銦(In), 鋁(Al) 和鎂(Mg)於氧化鋅奈米線中，並分析氧化鋅在各種不同濃度所呈現的晶體結構、光電、熱電、機械特性等等。然而藉由摻雜銦、鋁提升電的傳導與光學性質，同時提高載子濃度及電子移動率。其中添加鎂提升負溫度系數(NTC)特性應用於溫度控制與補償。本研究首先將氧化鋅靶材濺鍍於ITO基板製程薄膜做為種子層。第二部分為氧化鋅奈米柱成長使用於硝酸鋅 Zn(NO3)2和環六亞甲基四胺(HMT)並添加不同濃度的銦、鋁和鎂元素於水溶液法低溫合成。第三部以XRD分析材料在不同濃度成長的晶體方向，並以SEM/EDS檢測材料的表面形貌、結構尺寸及元素分布。以AFM儀器分析表面粗造度及電荷分佈。氧化鋅奈米柱機械特性以奈米壓痕器與微克式測試硬度、剛性、楊氏模數並以SEM觀察壓橫斷面形貌。奈米柱的光電特性以場發射效應、化學發光、光激發螢光及紫外光/可見光吸收光譜儀分析。經由摻雜不同濃度的銦、鋁其光電特性有顯著的影響，而摻雜Mg的氧化鋅在高溫環境中造成電阻下降並有明顯的提升NTC特性。最後以氧化鋅奈米柱製成元件並可應用於奈米發電機。

關鍵字

氧化鋅；摻雜；奈米柱；奈米發電機；熱電效應；電的特性；光學特性

並列摘要

Zinc oxide (ZnO) semiconductor materials have been widely used for applications in optoelectronic devices, sensors, lasers, transducers, and photovoltaic devices due to their wide direct energy band gap (3.37 eV), large excitation binding energy (60 meV). Most of all they demonstrate optical, field-emission properties by applied in optoelectronic area such as UV lasers, sensor and field-emission displays. In addition, ZnO to be part of hexagonal Wurtzite structure which one is functional materials, so that appears a similar family of nanostructures, such as nanowire and nanobelt structures, few special shape have been attracted , such as nanocages, nanocombs, nanorings, nanosprings, nanobows, and nanodisks. The present study investigates the effect of In, Al and Mg doping concentrations on thermoelectric and morphology of ZnO nanorods at various temperatures. By doping In, Al these method to enhance electrical and optical properties, so that ZnO has high carrier concentration, reasonable mobility, and low resistivity, and increase negative temperature coefficient (NTC) characteristic of Mg-doping ZnO for controlling temperature and compensate applications. This research comprised of second features. The first is ZnO thin films with a purity of 99.99% were deposited on ITO substrates using a radio frequency magnetron sputtering system. The thickness of the ZnO seed layers was measured as approximately 50 nm. The second is ZnO thin film was then used to grow ZnO nanorods from an aqueous solution at low temperature. An aqueous solution of ZnO(NO3)2 and hexamethyltetramine (HMT) was used for the In(NO3)3．6H2O/ Al(NO3)3•9H2O/ Mg(NO3)2．6H2O/, and Zn(NO3)2．6H2O mixed aqueous solution with various In/Al/Mg to Zn ratios. According to the doping In and Al effect, the ZnO structure, optics and electricity that characteristic had a significant effect on that In(NO3)3 concentration. The findings indicate that doping with Mg has a negative temperature coefficient effect on turn-on voltages and average resistance performance. Finally, a nanogenerator was fabricated and applied piezoelectric properties of the nanorods.