硫化鋅–氧化鋅之奈米核–殼結構的製備及特性研究

Abstract

奈米材料在化學、光電及機械性質上展現出其特殊功能以及發展的潛力。而奈米材料的製備方式是奈米材料研究上一個重要的研究領域，而在本論文中，研究的重點就在於一維奈米核–殼結構的製備。本篇論文中我們研究的目標分為兩部分，第一部份是利用溶液水熱法製備「硫化鋅–氧化鋅」的核–殼結構。而第二部分則是以原子層沉積技術配合陽極氧化鋁多孔性模板製備另一種「硫化鋅–氧化鋅」的核–殼結構。 在論文的第一部份中，我們是以溶液水熱法合成硫化鋅奈米棒。透過控制反應條件，可利用特定濃度的乙二胺作為反應溶劑，於200°C，經六小時以上的水熱法反應，可得 wurtzite 結構的硫化鋅奈米棒，奈米棒的直徑小於100 nm，長度約為數百nm。另外，我們發現可利用乙二胺作為溶劑，在室溫下以溶液共沉法合成出直徑為數百至數千nm、直徑為數十至數百nm之硫化鋅奈米棒。唯此法合成之產物尚包含未完全分解之ZnS．0.5en中間產物。我們對硫化鋅奈米棒進行650°C、3分鐘的通氧熱處理，將奈米棒的表面氧化，經由X-ray繞射及電子顯微鏡分析證明形成硫化鋅–氧化鋅的核–殼結構。核–殼結構之發光特性以可見光為主，主要發光峰值約位於490–500 nm，為藍綠光。 而在論文的第二部份，我們利用原子層化學氣相沉積技術，在陽極氧化鋁模板中製備氧化鋅奈米管陣列。並可藉由後續熱處理步驟降低缺陷含量，提升氧化鋅奈米管之光學性質。氧化鋅奈米管陣列在光激發光性質上具有共振效應，可提升紫外光發光強度。將氧化鋅奈米管陣列以硫化鋅水溶液進行硫化，可得到硫化鋅–氧化鋅的核–殼結構奈米管。經由XPS分析可以證明表層的氧化鋅已轉變為硫化鋅，形成核–殼結構之奈米管。硫化鋅的形成可能消除部份的缺陷，並伴隨著量子尺寸效應，使核–殼結構之光學性質較氧化鋅奈米管提升約6倍。 本研究以兩種方法合成硫化鋅–氧化鋅的一維奈米核–殼結構，有助於提升單一材料之光學性質，未來可應用於發光元件或平面顯示器技術上。

Nanomaterials have extraordinary functionality and strong potential for future development. Preparation methodology of nanomaterials have since been an important research field. In this work our emphasis lays on the preparation of one dimensional core-shell structure. We use two different ways to fabricate ZnS-ZnO core-shell structure, namely hydrothermal method and atomic layer deposition method. Wurtzite ZnS nanorods are obtained through hydrothermal processing for 6 hours under 200℃ using ethylenediamine of specific concentration as solvent. The diameter of the nanorods is smaller than 100 nm and the length of them is around several hundred of nanometers. Moreover, ZnS nanorods are also synthesized by codeposition under room temperature using ethylenediamine as solvent. These rods have a length from 500 to 2000 nm and a diameter from 20 to 150 nm. However, ZnS nanorods synthesized in this way contain un-decomposed ZnS 0.5en. Surfaces of the rods are oxidized by heating under 650℃ for 3 mins in an oxygen atmosphere. ZnS-ZnO core-shell structure is examined by XRD and SEM. The luminescence of core-shell structure is mainly in the visible region, with its PL peak at 490-500nm. In the second part we use atomic layer chemical vapor deposition technique to deposit ZnO nanorod array in an anode aluminum oxide template. The optical properties is enhanced by reducing defect concentration through post-annealing processes. Resonance effects are observed, enhancing UV emission intensity. ZnS-ZnO core-shell nanotubes are obtained by the sulfurating the ZnO nanorod array using NaS solution. Transformation of ZnO to ZnS is proofed by XPS analysis. The optical properties of ZnS-ZnO core-shell structures have improved six times over ZnO nanorods. We assume the formation of ZnS, which diminishes defects and the quantum-sized effect may be the reason. This research synthesized ZnO-ZnS one dimensional core-shell structure in two different ways, which both offer better optical properties than single material. This may have future potential for application in light emitting devices and flat panel display technology.