氧化鋅的奈米結構成長與應用研究

Synthesis and Applications of ZnO Nanostructures

張育誠(Yu-Cheng Chang)

指導教授 ： 陳力俊

國立清華大學/工學院/材料科學工程學系/博士(2007年)

摘要

一維奈米結構如奈米棒、奈米線與奈米管因為它們獨特的物理性質而引發廣泛的興趣和研究。本研究利用水熱法的方式，成長具有針狀結構的氧化鋅奈米陣列於已沈積氧化鋅核種之矽基版上。氧化鋅的核種層有助於成長直立的氧化鋅奈米棒。針狀結構的氧化鋅奈米結構成長於基版朝下且面向溶液，並固定於接近上層溶液的位置。在相同反應條件中溫度變化有利於成長不同長度的針尖。從陰極放光圖譜顯示針狀結構的氧化鋅陣列具有非常強且尖銳來自於能隙的紫外光放光特性，而且沒有來至於氧缺陷所導致的綠光放光。
在矽基版上成長具有二維反蛋白石結構之網狀氧化鋅的奈米棒，利用排列單層的聚苯乙烯球作為模版鍍上適當厚度的金薄膜，進一步成長氧化鋅的奈米棒於球與球之間隙，最後去除聚苯乙烯球即可形成具有網狀結構的氧化鋅奈米棒。本研究成功的製備出二維的網狀氧化鋅奈米棒，並且在綠光波長位置具有光子晶體能隙。此結合奈米球模版技術與水溶液成長技術可以提供大面積、便宜與低溫的製備條件，將有利於製備光子晶體的結構。
利用水溶液成長與向下成長的技術可以有效成長出氧化鋅的奈米塔陣列於在矽基版上已長好氧化鋅的奈米棒陣列。抗壞血酸的濃度能控制成長方向與具有不同層數的奈米塔，並且有效的降低成長時間。在高濃度的條件下可以成長出具備六角形金字塔結構與類似雲母片狀的結構。氧化鋅的奈米塔具有低的起始電場與侷限電場，顯示其在場發射裝置的應用潛力。氧化鋅奈米塔具有極佳的紫外光放光的特性，且具備高的藍光位移與完全無氧缺陷的放光，此具備深紫外光放光特性，將可提供未來於光放光元件的應用。極性面的概念有利於瞭解氧化鋅奈米塔的成長機制。藉由適當的反應條件有利於成長具有晶圓大小的氧化鋅奈米塔。此一大面積之奈米塔將可有效的提供於先進元件的應用，例如：場發射、紫外光雷射與染料敏化太陽能電池的應用。

關鍵字

氧化鋅 ； 奈米針 ； 奈米棒 ； 奈米塔 ； 水溶液成長法

並列摘要

One-dimensional nanostructures, such as nanorods, nanowires and nanotubes, have attracted great attention because of their peculiar optical, electrical and mechanical properties. Tapered ZnO nanorod, herein called nanoneedle, arrays have been grown on ZnO-coated silicon substrate by a hydrothermal downward growth process. The ZnO seeds layer facilitated the growth of aligned nanorods. The nanoneedles were grown with the substrate placed flush with the surface of the reaction solution and facing downward. The correlation between the depletion of solution and reaction temperature was exploited to control the length of the tapered portion of ZnO nanoneedles for the same solution. The ZnO nanoneedle arrays exhibit very strong and sharp ultraviolet emission from band gap transition and almost no green emission attributed to singly ionized oxygen vacancies in the cathodoluminescence spectrum.
Self-assembled 2D inverse opal ZnO nanorod networks have been grown on silicon. The 488 nm PS nanospheres monolayers were used as the mold to grow the ZnO nanorod networks through the steps of self-assembly of monolayer PS nanospheres, deposition of Au buffer layer, catalytic growth of ZnO seeds layer on Au, growth of ZnO nanorods on ZnO seeds layer and removal of PS nanospheres. The work represents the successful growth of 2D ZnO photonic crystal with band gap at the green light emission region for the first time. The combination of nanosphere lithography and aqueous chemical growth provides a large-scale, facile and low cost fabrication method at low temperature, which shall be of tremendous value in practical applications of the grown photonic crystals.
Aligned ZnO nanopagoda arrays have been grown on the silicon substrate with ZnO nanorod arrays by a hydrothermal and downward growth process. The concentration of bid-friendly ascorbic acid (vitamin C) was used to control the growth direction and the degree of lamination of ZnO nanostructure with vastly reduced reaction time (from 24 to 2 hrs). Low turn-on and threshold fields indicate that ZnO nanopagodas are promising for applications in field emission devices. The ZnO nanopagodas exhibit very prominent blue shift (10 nm) of UV emission and almost no green emission attributed to singly ionized oxygen vacancies at room temperature. The enhancement in deep-UV optical properties shall be advantageous in applications for nanoscale light-emitting devices. The polar surface concept can be useful to understand the ZnO growth mechanism of nanopagodas. The appropriate substrate and reaction condition lead to the growth of ZnO nanopagoda arrays with wafer-scale production. The large-scale ZnO nanopagoda arrays shall be very useful in fabricating the novel devices, such as field emitter, ultraviolet laser and dye-sensitized solar cells.

並列關鍵字

ZnO ； nanoneedle ； nanorod ； nanopagoda ； aqueous chemical growth method

參考文獻

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