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  • 學位論文

新穎奈米半導體複合材料的物理性質研究

Investigation of Novel Physical Properties of Composite Materials based on Nanostructural Semicondocutors

指導教授 : 陳永芳

摘要


在本篇論文中,我們提出了幾種新穎奈米半導體複合材料並研究其物理性質。我們的設計包含有: 1. 液晶-晒化鎘奈米管新穎複合元件;我們率先提出的這個構想,是基於巧妙利用液晶與晒化鎘奈米管兩者之間不同的物理特性,可以達到用電壓來操控半導體發光偏極性的效果。我們的成果可以達到相當理想的72%的操控效率,這個結果是目前最高的數值。我們設計的這種智慧型元件,還具有相當大的面積,相信可以應用在LED,平面顯示器等元件上。 2. 液晶-鎳奈米棒新穎複合元件;我們首先提出這種全新的結構,來完成以控制電壓的方式,操控磁偏極性的目標。目前要達到好的操控效果,需要克服嚴苛的長晶要求,及相當高的成本。我們提出完全不同於目前思維的方式,以一種簡單且低成本的方法完成磁電效應的轉換。我們得到的效率高達40%,足可比擬目前可以達到的最高效率。這個設計與其所達到的良好效果,相信可以在磁性資料儲存元件上加以應用。 3. 晒化鎘奈米雷射:奈米化是絕對的趨勢,而將雷射達到奈米化,有著非常豐富的應用前景與學術研究價值。在此我們成功的設計出一種前所未有的奈米雷射元件。我們將半導體置入陽極氧化鋁的空腔結構中,利用WGM共振的原理,激發出奈米雷射。我們更進一步的建立了理論上的模型,做為這種結構激發出雷射的條件依據。這種簡易而又低成本的設計,除了可以用來做奈米雷射之外,還可以應用在LED等發光元件的設計上,應用潛力無窮。 4. 利用表面電漿子增強晒化鎘發光強度的元件結構;增強LED的發光強度一直是具有挑戰性的課題。我們設計的結構,可以讓表面電漿子在其中傳播,而這個傳播型的表面電漿子已證明具有相當大的輻射強度,所以將發光半導體量子點置於此結構內,可以預期會大大的增強它的發光效率。我們所做出的元件,證明它的發光效率比單純的量子點發光效率足足多了54倍。並且也觀察到在不同的表面電漿結構中,可以增強的光波波長也不同。這個結構在LED的應用上相信會有很大的價值。

並列摘要


In this thesis, we design several composite materials based on nanostructural semiconductors. Two liquid crystal devices with built-in semiconductor nanotubes and ferromagnetic nanorods have been designed, fabricated, and characterized. The composites consisting of semiconductors nanomaterials and anodic aluminum oxide nanocavities have been studied. In addition, CdSe quantum dots embedded in periodic gold nanoarrays have also been investigated. Quite intriguing novel propertied have been discovered, which should be very useful for the development of new optoelectronic devices 1. Electrical manipulation of physical anisotropy in the composite of liquid crystals and nanomaterials For liquid crystal devices with CdSe nanotubes, we demonstrate that the degree of polarization can be dramatically changed from 72% to a negligible level, with an applied voltage of 3V. The ability to well control the emission anisotropy should open up new opportunities for nanostructured semiconductors, including optical filters, polarized light emitting diodes, flat panel displays, and many other chromogenic smart devices. Beside, the fabrication of liquid crystal devices compounded with built-in ferromagnetic nanorods has been studied. Electrically assisted magnetization switching has been demonstrated through the effect that the electrical manipulation of magnetic nanorods. In view of the well established technology of liquid crystals display, our results pave a key step for the practical application of new device paradigms based on magnetoelectric effect, including electric field-controlled magnetic data storage, transducers, attenuators, and spintronics. 2. Room-temperature nanolaser from CdSe nanotubes embedded in anodic aluminum oxide nanocavity arrays The foremost observation of WGM-lasing for CdSe nanotubes embedded in cylindrical nanocavities based on anodic aluminum oxide (AAO) template has been reported. Low threshold pumping level for the sample was observed, due to the high nanocavity Q. The natural cavity or waveguide formation in AAO pores suggests a simple approach to obtain a nanolaser cavity without cleavage and etching. In addition, the lasing spectrum shows strong mode selection and single constructive interference peak, due to the interferential coupling of WGMs at the outer boundary. The observation of laser action in these nanotube arrays is readily to be extended to many other systems with different emission wavelengths. Our study shown here therefore should be very useful for the future development of nano-optoelectronic devices. 3. Enhancement of emission from CdSe quantum dots induced by propagating surface plasmon polaritons The emission property of CdSe quantum dots arising from surface plasmon polariton of interconnected gold particles has been studied. Variation of the structural parameters allows us to tune the surface plasmon resonance to the emission band of quantum dots. It results in an enhancement up to 54 times in the external quantum efficiency. The time-resolved photoluminescence shows that the electron-hole recombination rate in CdSe QDs is enhanced, when their spontaneous emission is coupled with a gold surface plasmon mode. Our strategy for the enhancement of luminescence efficiency from semiconductor quantum dots should be useful for the creation of high efficiency solid state emitters.

參考文獻


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