Ph.D. (Physics) / Please refer to full text to view abstract

>Magister Scientiae - MSc / Photovoltaic (PV) devices based on inorganic-organic hybrid active layers have been extensively studied for over a decade now. However, photoactive hybrid layers of material combinations such as rr-P3HT and SiNWs still require further exploration as candidates for solar cell (SC) fabrication, due to favourable optical absorption and charge carrier mobility associated with them respectively. The ultimate goal of the study is to fabricate ITO/PEDOT:PSS/rr-P3HT:SiNWs/Al SCs with different SiNWs content and investigate the different parameters or factors influencing the performance of these cells. The vertically aligned SiNW arrays on a Si wafer were synthesised via metal assisted chemical etching (MACE) and a method of chemically detaching these wires was developed. The average length and the diameter of the SiNWs obtained were 4.5 μm and 0.2 μm, respectively. Different weight ratios of as-synthesised SiNWs were then incorporated within rr-P3HT to form different hybrid solutions, i.e. rr-P3HT: 0.3 wt% SiNWs, rr-P3HT: 0.7 wt% SiNWs and rr-P3HT: 1.3 wt% SiNWs. In addition, a pure rr- P3HT solution was made for reference purposes. SEM characterisation shows that the SiNWs are randomly distributed across the active area, and that the film becomes progressively inhomogeneous upon addition of SiNWs, whereas the TEM characterisation revealed that there is no chemical interaction between the rr-P3HT and SiNWs. The UV-Vis and PL spectra suggest that there are changes in absorption and emission characteristics upon SiNW incorporation into the rr-P3HT matrix, which may have impacted the charge transfer .The electrical properties of the different hybrid films were probed using Hall Effect measurements, which revealed that the conductivity increases with the increase in the concentration of nanowires (NWs). The increase in conductivity upon the addition of SiNWs in the rr-P3HT matrix was related to an increase of the mobility (μ) of charge carriers in the hybrid films.

Based on rst principles calculations the structural, mechanical stability and electronic properties of molybdenum chalcogenides 2H-MoX2 (X = S, Se, Te) have been studied using density functional theory (DFT). The generalized gradient approximation (GGA) proposed by Perdew, Burke and Ernzerhof (PBE) was employed together with the projector augmented plane wave (PAW) method. The van der Waals interactions in the Grimme (DFT-D2) and Lundqvist and Langreth (vdW-DF) approximations have been added on top of PBE or revised PBE in order to take into account the weak interactions between layers of 2H-MoX2 (X = S, Se, Te). The structural properties include the equilibrium lattice parameters, the cohesive energy and the formation energy. Besides we have studied the mechanical stability of these compounds by examining the elastic constants using the PBE, vdW-DF, and DFT-D2 approximations. Other quantities related to the mechanical properties such as the Young's modulus, the Poisson's ratio and the bulk modulus were also calculated. Electronic properties of bulk 2H-MoX2 (X = S, Se, Te) have been investigated using density functional theory (via band structure and projected density of state), and a partially self-consistent GW (GW0) approximation. We have investigated electronic properties ( band structure) for monolayers 1H-MoX2 (X = S, Se, Te) using a single shot GW (G0W0) approximation. Optical properties for monolayer 1H-MoX2 (X = S, Se, Te) were studied using the Bethe-Salpeter equation (BSE).

A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy / Raman and photoluminescence (PL) spectroscopy techniques were used to investigate the mechanical properties of diamond and cubic boron nitride (cBN) by optical means. Both these materials have extreme mechanical properties that make them the material of choice for many industrial applications, ranging from cutting and grinding to wire-drawing dies. The results obtained on single crystal diamond, polycrystalline diamond (PCD) and cBN are summarised below. Micro-Raman and photoluminescence (PL) spectroscopy were used to map the threedimensional (3D) stress and deformation distributions surrounding a plastic impression made in a synthetic, type Ib single crystal diamond. Using data from the Raman peak position, a 3D map of the stress contours surrounding the impression was generated, while the Raman width data yielded a map of the plastic deformation volume. The stress contours compare favorably with the resolved shear stress contours calculated for diamond. PL intensity maps of the zero phonon line (ZPL) associated with the [N-V]– defect centre at 1.945eV provide images of the extent of vacancy formation and movement during the impression process. Data concerning the position and width of the ZPL correspond well with the Raman results. Polycrystalline diamond (PCD) tools commonly consist of a PCD layer sintered onto a cobalt-tungsten carbide (Co-WC) substrate. These tools are used in diverse applications and both the magnitude and distribution of the stresses in the PCD layer affect tool behavior. These stresses in sample drillbits were investigated by means of micro-Raman spectroscopy. Cyclic annealing of a sample drillbit to 600 oC shows that the tool properties are retained after 5 cycles, while similar cycling to 800 oC resulted in a permanent decrease of the average surface compressive stress. This implies a reduction in the drillbit’s ability to resist crack formation and propagation and is thus a degradation of the tool properties. The method of Raman mapping of stress and deformation in diamond was also applied to single crystals of cBN. Indentations on cubic boron nitride (cBN) crystals and polycrystalline cubic boron nitride (PcBN) composites were mapped and the shifts of the cBN Raman lines from their unstressed positions used to quantify the residual stresses in the boron nitride due to the deformation brought about by the indentation. These were found to be of the order of 1 GPa. vi These measurements illustrated for the first time the use of Raman spectroscopy to study residual stresses in boron nitride. Defects in cBN were studied using photoluminescence spectroscopy at low temperature (< 10 K) of two types of cBN irradiated at ambient temperature with 1.9 MeV electrons. All the samples were small (<1 mm diameter) single crystals of cBN. Three defect centres (with narrow lines at 2.28 eV, 2.15 eV and 1.98 eV) were introduced in both the amber-coloured and blackbrown coloured samples by the irradiation. The amber coloured sample also showed a defect centre (at 1.65 eV) that is present before and after irradiation. Line shape analysis of the zero phonon lines of all three irradiation-induced centres showed that the lines are predominantly Gaussian in character, suggesting that linetype defects such as dislocations are a prevalent characteristic of these crystals. Raman spectroscopy of cBN single crystals as a function of temperature was performed over a wide temperature range from 4 K to 1373 K. The low temperature measurements extended the data previously reported in literature, as this data ranged from room temperature upwards. It was concluded from the shift of Raman peak position with temperature that both linear expansion and anharmonic effects were required to adequately account for the observed data. This is in agreement with previously published findings. Both 3- and 4-phonon processes were required to account for the observed linewidths as a function of temperature, again in agreement with literature. The results presented here and in the associated journal publications illustrate clearly how optical spectroscopy techniques can serve as non-destructive characterisation tools for the mechanical properties of ultra-hard materials.

Estudou-se a polimerização do álcool furfurílico líquido na interface nonômero-catalisador delimitada pelo interior de um tubo de vidro capilar. A superfície do álcool furfurílico líquido contido em um tubo de vidro de diâmetro interno inferior a 5.4mm foi exposta aos vapores de ácido clorídrico concentrado, o catalisador. Observou-se a formação de uma película auto-organizada e colorida na interface que, sob a ação da gravidade, cai para o interior do tubo com velocidade constante. O espectro de absorção óptica identificou a formação de oligômeros com picos de absorção em 570nm, 650nm, 770nm e 930nm, sendo a de 650nm a mais de peso molecular dos oligômeros difere fortemente daqueles formados por catálise homogênea. A condutância dessas películas foi observada medindo-se a resistência elétrica de películas formadas sobre uma placa invertida de vidro plano / The polymerization of furfuryl alcohol in the interface alcohol-concentrated hydrochloric acid vapor was studied inside glass tubes whose internal diameter were smaller than 5.4mm. Shortly after exposition of furfuryl alcohol to the acid vapor an auto organized bluish pellicle is generated that under gravity falls inside the tube with constant velocity. The observed optical absorption spectrum peaks at 570nm, 650nm, 770nm and 930nm were attributed to oligomers with 3, 5, 7 and 9 mers, respectively. The optical absorption band at 650nm being the stronger. The oligomers molecular weight distribution so formed was found to strongly differ of the ones formed by homogeneous catalysis. The electrical conductivity of these pellicles, made of conjugated oligomers, were observed measuring the electrical resistance of pellicles specially made on the flat inverted glass plate

by Kwong-hung Tam = 低壓化學氣相沈積硅膜之電學特性 / 譚廣雄. / Thesis (M.Ph.)--Chinese University of Hong Kong, 1985 / Bibliography: leaves 102-105. / by Kwong-hung Tam = Di ya hua xue qi xiang chen ji gui mo zhi dian xue te xing / Tan Guangxiong.

由於表面等離子體激元可以將電磁場限制在金屬表面，從而產生強烈的場強增強效果，因此在納米光子學和生物光子學方面具有廣泛的應用價值，其中包括高性能發光二級管、光伏電池、超高分辨率光學成像和超靈敏分子檢測等。尤其在單分子和醫學診斷方面，基於表面等離子體共振的生物傳感器獲得了越來越多的青睞。本論文包括兩部份。第一部份著重討論二維週期性洞陣列的表面等離子體特性，而第二部份則是研究這種洞陣列結構在表面等離子體共振傳感方面的應用。 / 在第一部份中，表面等離子體模式被分為非簡並模式(m，O) 和簡並模式(m，±n)兩種情況分別加以討論。首先，結合實驗結果和理論模型，我們對非簡並模式的衰減壽命和激發效率進行了研究。通過光干涉光刻法和薄膜沉積技術，一系列不同幾何結構的洞陣列樣品被製備出來，且這些樣品具有很高的重複性。利用角分辨色散關係進行模式識別以及確定這些模式的衰減壽命和激發效率。通過調整起偏器和檢偏器的相對方向，表面等離子體模式的非輻射和輻射衰竭均可加以研究。結果發現，衰減壽命強烈依賴於單洞的幾何結構，而且這種行為可以用簡單的靜電模型并考慮高階修正加以解釋。從非輻射衰減和輻射衰減平衡的角度出發，激發效率對幾何結構和共振波長的依賴性也可以理解。對於簡并模式，由於存在稱合，對稱模式和反對稱模式分別被p 偏振激發和S偏振激發。它們的對稱性和對於衰減壽命和共振波長的修正可以用干涉法和模式耦合理論來理解。最後，利用多模耦合方程，我們對色散關係圖譜隨著洞深度增加而演化的情況也進行了探討。 / 第二部份對基於表面等離子體共振的生物傳感器與陣列幾何結構的關係進行了研究。結果發現，激發效率和衰減壽命對表面等離子體共振傳感器的分辨率都起到了關鍵性作用。在共振中，峰值高度和帶寬主要由表面等離子體的衰減速率控制。較低的衰減速率導致較清晰的峰值線型，從而產生較高的傳感器分辨率。因此，通過調整陣列的幾何結構以產生非常低得輻射衰減速率，表面等離于體共振傳感器的品質因數可高達104.8/RIU ，這已經超過了基於梭鏡和納米粒子對應器件的性能表現。 / Surface plasmon polaritons (SPPs) generate a strong localized electromagnetic field on metal surface and thus are promising for nano- and bio-photonics including high performing light-emitting diodes and photovoltaic cells, super-high resolution optical imaging, ultra-high sensitive bimolecular detection, etc. In particular, the application of SPPs on surface plasmon resonance (SPR) biosensor has drawn much more attention recently because of the attempt to realize single molecule detection in medical diagnosis. / This thesis contains two parts. The first part focuses on studying the basic plasmonic properties of two-dimensional periodic hole arrays while the second part concentrates on the application of hole arrays on SPR sensing. / In the first part, SPPs modes on hole arrays are classified into nondegenerate mode (m, 0) and degenerate mode (m, ±n). For nondegenerate mode, its decay lifetime and generation efficiency are studied both experimentally and theoretically. By combining interference lithography and thin film deposition, a set of arrays with a wide range of geometry has been fabricated with high reproducibility. The dispersion relations of arrays are studied by angle-dependent reflectivity for mode identification and detenninations of SPP decay lifetime and generation efficiency. In particular, through orienting the polarization of the specular reflection either parallel or orthogonal to that of the incidence, we can access both the nonradiative and radiative decays of SPPs at different resonance wavelengths. As a result, it is found that decay lifetime is strongly dependent on the geometry of single hole and its behaviors can be understood by using a simple quasi-static model taking into account of the higher order correction as well as numerical simulation deduced by finite-difference timedomain. The dependence of generation efficiency on hole geometry or resonance wavelength can be understood in tenns of trade-off between nonradiative and radiative decay rates. Once these two decay rates equals to each other, the optimum generation efficiency is realized and the field enhancement gets the maximum. And the optimum parameters can be achieved by adjusting the hole geometry or the resonance wavelength. For degenerate mode, due to the coupling between (m, +n) and (m, -n) modes, a symmetric and an anti-symmetric modes are excited under pand s-polarized excitation, respectively. Their symmetries and modifications to the decay lifetime and resonance wavelength can be understood by using the interference method and coupled mode theory. Finally, generalized coupled mode equations are employed to know about the evolution of dispersion relation as hole depth increases. / The dependence of SPR biosensor on the generation and decay of SPPs are studied in the second part. Both the generation efficiency and decay lifetime of SPPs are found to be critical in governing the resolution of SPR biosensor. In SPR, the peak height and linewidth are primarily controlled by the decay rate of SPPs. Lower decay rate leads to sharper peak profile, which results in higher SPR resolution. Therefore, by tailoring the geometry of hole arrays to achieve a very low radiative decay rate, a SPR biosensor with figure of merit (FOM) reaching l04.8/RIU can be realized, which surpasses those of prism and nanoparticle counterparts. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Zhang, Lei = 表面等離子體激元對於週期性金屬納米結構幾何形狀的依賴性及其在生物傳感中的應用 / 張磊. / "November 2011." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 116-125). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese. / Zhang, Lei = Biao mian deng li zi ti ji yuan dui yu zhou qi xing jin shu na mi jie gou ji he xing zhuang de yi lai xing ji qi zai sheng wu chuan gan zhong de ying yong / Zhang Lei. / Chapter Chapter1 --- Introduction --- p.1 / Chapter Chapter2 --- Theoretical Background --- p.7 / Chapter 2.1 --- Maxwell's equations --- p.7 / Chapter 2.2 --- Classic electromagnetic theory for dielectric properties of matter --- p.9 / Chapter 2.3 --- Surface plasmon polaritons at the dielectric/metal interface --- p.11 / Chapter 2.4 --- Excitation of surface plasmon polaritons --- p.16 / Chapter 2.4.1 --- Prism coupling --- p.17 / Chapter 2.4.2 --- Grating coupling --- p.17 / Chapter 2.5 --- lones calculus --- p.19 / Chapter 2.6 --- Finite-difference time-domain method --- p.22 / Chapter Chapter 3 --- Sample Preparation --- p.25 / Chapter 3.1 --- Interference lithography --- p.25 / Chapter 3.1.1 --- Substrate preparation --- p.26 / Chapter 3.1.2 --- Exposure --- p.27 / Chapter 3.1.3 --- Pattern development --- p.30 / Chapter 3.2 --- Thin film deposition --- p.30 / Chapter Chapter 4 --- Experimental Setups and Calibration --- p.33 / Chapter 4.1 --- Experimental setup for measuring dispersion relation --- p.33 / Chapter 4.2 --- Experimental setup calibration --- p.35 / Chapter 4.2.1 --- Calibration of spectrometer --- p.36 / Chapter 4.2.2 --- Calibration of movement stages --- p.38 / Chapter 4.3 --- Data presentation for dispersion relation --- p.40 / Chapter 4.4 --- Summary --- p.41 / Chapter Chapter 5 --- Understanding of Fundamental Properties of SPPs --- p.43 / Chapter 5.1 --- Excitation of SPPs on 2D hole arrays --- p.44 / Chapter 5.2 --- Properties of non degenerate modes and theoretical explanation --- p.53 / Chapter 5.2.1 --- Dependence of lifetime on hole geometry and theoretical explanation --- p.55 / Chapter 5.2.2 --- Dependence of generation efficiency on hole geometry and theoretical explanation --- p.63 / Chapter 5.3 --- Properties of degenerate modes and theoretical explanation --- p.70 / Chapter 5.3.1 --- Dependence of properties of degeneration modes on hole geometry by FDTD --- p.72 / Chapter 5.3.1.1 --- (0, ±l)[subscript s,a] modes --- p.72 / Chapter 5.3.l.2 --- (-1, ±l)[subscript s,a] modes --- p.76 / Chapter 5.3.2 --- Understanding of excitation of degenerate modes by using interference method --- p.79 / Chapter 5.3.3 --- Understanding of coupling between degenerate modes by using coupled mode theory --- p.85 / Chapter 5.4 --- Evolution of dispersion relation as hole depth increases --- p.90 / Chapter 5.5 --- Summary --- p.95 / Chapter Chapter 6 --- Surface Plasmon Resonance Based Label Free Biosensor --- p.98 / Chapter 6.1 --- Basics of surface plasmon resonance (SPR) based biosensor --- p.98 / Chapter 6.2 --- State-of-the-art SPR biosensor --- p.101 / Chapter 6.3 --- SPR biosensor by using 2D metallic hole arrays --- p.102 / Chapter 6.4 --- Summary --- p.111 / Chapter Chapter 7 --- Conclusions --- p.112 / References --- p.116 / Publications --- p.126

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by Hui Koon-chung = 由電子束照射引起氧化金屬膜覆蓋的氧化鋅之光學特性 / 許冠中. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (leaves 87-89). / Text in English; abstracts in English and Chinese. / by Hui Koon-chung = You dian zi shu zhao she yin qi yang hua jin shu mo fu gai de yang hua xin zhi guang xue te xing / Xu Guanzhong. / ABSTRACT --- p.i / ACKNOWLEDGMENTS --- p.iii / TABLE OF CONTENTS --- p.iv / LIST OF FIGURES --- p.vi / LIST OF TABLES --- p.x / Chapter 1. --- Introduction --- p.1 / Chapter 1.1 --- Motivation --- p.1 / Chapter 1.2 --- Overview of ZnO / Chapter 1.3 --- Overview of the Thesis / Chapter 2. --- Experimental conditions and procedures --- p.11 / Chapter 2.1 --- Samples preparation / Chapter 2.2 --- Optical and electrical Characterizations of ZnO / Chapter 2.2.1 --- Setup of cathodoluminescence (CL) spectroscopy / Chapter 2.2.2 --- Setup of photoluminescence (PL) spectroscopy / Chapter 2.2.3 --- Setup of photoconductivity measurement / Chapter 2.2.4 --- Setup of atomic force microscopy AFM / Chapter 2.2.5 --- X-ray photoelectron spectroscopy (XPS) / Chapter 3. --- Experimental results and data analysis --- p.21 / Chapter 3.1 --- The luminescence of ZnO --- p.21 / Chapter 3.2 --- Effects of metal capped layer in luminescence --- p.24 / Chapter 3.3 --- Optical memory effect of A1 capped ZnO --- p.28 / Chapter 3.4 --- The XPS study ofAl capped ZnO --- p.33 / Chapter 3.5 --- Optical properties and photoconductivity studies of AlOx-capped ZnO --- p.35 / Chapter 3.6 --- Time- and Electron-dose dependent CL of AlOx capped ZnO --- p.41 / Chapter 3.7 --- Dependence of band-edge enhancement on Deep Level to band-edge emission ratio --- p.53 / Chapter 3.8 --- Temperature-dependent CL of AlOx capped ZnO --- p.56 / Chapter 3.9 --- Electrical measurement of luminescence enhanced ZnO --- p.64 / Chapter 4. --- Discussion --- p.69 / Chapter 4.1 --- General discussion --- p.69 / Chapter 4.2 --- The effect of AlOx capping on the optical properties of ZnO --- p.70 / Chapter 4.3 --- The action of e-beam irradiation on the enhancement of band-edge emission --- p.73 / Chapter 4.4 --- The function of AlOx layer when under electron irradiation --- p.83 / Chapter 5. --- Conclusions --- p.85 / Reference --- p.87

基於表面等離子體的納米器件已經在近幾十年引起了十分廣泛的興趣因為其對於半波長光子器件，光學傳感，光譜學以及光學捕獲有著廣大的應用前景。表面等離子體是一種被限定於金屬和介質介面上的一種光子-電子混合模式，而且它具有許多吸引人的特質，比如對金屬表面周圍環境極其敏感，納米尺度範圍的光學電磁場局域和場增強，以及對鄰近物體極強的場強梯度捕獲力。雖然這些特性都已經分別被廣泛的研究過，但從光學捕獲的角度去實現光學傳感的方案並還沒有引起大量的關注。很明顯，在納米尺度範圍內操縱目標的可能性將使得新的納米器件具有高的光學探測性能和多功能性。為了涉及這個論題，本項目包括新穎的等離子體納米器件的研究，這些納米器件將能夠提供獨特的功能，在光學傳感，表面增強拉曼散射，以及光學捕獲方面。 / 在第一部分設計中，構建了一種基於雙層金屬納米條陣列的耦合系統。這樣的系統具有簡單的結構，易於加工和集成於微流系統的優點。由於這個系統內的光場耦合，場強可以進一步的被加強，這樣的特點有助於提高系統的敏感特性，尤其是通過強的光場來捕獲一些金屬的納米顆粒後。這個系統的光學共振條件可以從理論上進行模式分析得到。然後二維時域有限差分法證實了理論的分析而且進一步證明了利用該系統於光學傳感和捕獲的可能性。結果表明此系統的光學敏感度約為200nm/RIU，通過光學捕獲的金屬納米顆粒引起的近場調製和場增強可以使得表面增強拉曼散射的增強因數達到10⁹ 到10¹° 的高度。 / 在第二部分的設計裡，金納米環結構被證實了可以成為一個強大的工具作為表面等離子體納米光鑷來抓獲金屬納米顆粒。首先，金屬納米環具有很多優點比如對入射光的偏振不敏感，很寬的可調的共振範圍，有環的內腔周圍和內部有著均勻的光學場增強，以及很容易製備。這裡的設計著重于納米環在入射波長為785nm 的新穎的光學捕獲特性以及表面增強拉曼散射的性能。三維的時域有限差分法被用來計算結構的光學回應，以及麥克斯韋應力張量法被用來計算光學受力分佈情況。計算結果表明對於一個有20nm 大小的金納米顆粒球，納米環結構有最大的光學捕獲勢阱約32 KgT 。由於納米環結構周圍存在多個捕獲勢阱，使得其對目標捕獲顆粒具有約10⁶nm³ 的非常之大的有效體積。而且，被捕獲的顆粒會進一步的導致一些納米間隙的形成，這些納米間隙又會使得近場增強達到約160 倍的高度，這使得在實際應用中10⁸ 的表面增強拉曼散射的增強因數成為可能。 / 在第三部分的設計裡，全光納米操縱的概念被提出並證實，因為這樣的概念拓展了等離子體光鑷的一個極其重要的功能，那就是被捕獲的分子可以在捕獲和區域內被任意的操縱和轉移，而且這個區域是納米尺度的。設計的系統由梯度形金屬納米盤組成，這些納米盤具有不同的直徑，這使得它們支援不同波長的表面等離子體共振。通過改變入射光的波長和旋轉入射光的偏振態，就可以將捕獲的目標從一個納米盤轉移到另一個納米盤。三維的時域有限差分法和麥克斯韋應力張量法被用來證實了所提出的觀點。計算結果表明被捕獲的目標感受到的捕獲勢阱深度高達5000kgT/W/μm²，最大的光學轉矩約為336pN·nm/W/μm²，而且總的有效捕獲體積可達到10⁶nm³ 。在這部分的結尾，討論了所設計的系統在光學傳感方面潛在的應用前景。 / 在最後的部分裡，展示了一個實驗的證明來說明等離子體納米光鑷對目標捕獲的觀測問題，因為這樣的觀測對往後近期的相關實驗來說是首先要關心的問題。雖然兩種途徑已經在別處被證實了，分別是通過觀測系統的透射光的強度變化和系統共振波長的改變，來監測表面等離子體納米光鑷近場捕獲行為的發生，但是在這個部分裡，等離子體納米光鑷和表面增強拉曼傳感技術被結合在了一起並且被證實了這是另一種有效的方法用於觀測捕獲行為的發生。在本實驗中兩束鐳射光束被為別用來激發等離子體納米光鑷和表面增強拉曼信號，一束是633nm 的鐳射，另一束是785nm 的鐳射。表面等離子體納米光鑷簡單地由熱蒸鍍並熱退光的金顆粒納米島墊底構成，這個墊底的共振峰被調製到緊靠633nm 的位置。目標顆粒是由光化學生長合成的銀納米十面體，這些十面體被綁定了4-巰基苯甲酸分子的單分子層，且具有遠離633nm 和785nm 的共振峰。由於當等離子體納米光鑷被激勵的時候目標顆粒會被捕獲到近場的熱點內，這時近場的光場就會被極大的增強，所以表面增強拉曼的信號就會出現。這個過程也被用數值模擬的方法（三維時域有限差分法和麥克斯韋應力張量法）闡明了。更進一步的，當等離子體納米光鑷不被激勵的時候，被捕獲的目標顆粒可以被釋放掉，那樣表面增強拉曼的信號就會消失掉。所以，本設計不僅提供了一種強有力的探測等離子體光鑷捕獲行為的方法，而且能夠成為一種在生物探測方面可重複利用的“捕獲并傳感“的平臺。 / Surface plasmons (SPs) based nanodevices have attracted much research interest in recent decades due to their powerful application potentials for subwavelength optical circuits, optical sensing, spectroscopy, and optical trapping. SPs are the hybrid photon-electron modes bound at the interface of conductors and transparent materials, and they have lots of attractive properties such as sensitive to the changes of environment around the interface, strong optical field localization and enhancement in nanoscale domain, and strong field intensity gradient forces to trap the adjacent objects. Even though these properties have been widely investigated, their application in optical sensing based on the plasmonic optical trapping strategy remains largely unexplored. Clearly, the possibility of manipulating objects within the nanometer regime will enable new nanodevices that offer high optical detection performance and multiple-functionality. With the aim to address this issue, this project involves the study of novel plasmonic nanodevices that provide unique functionality in optical sensing, surface-enhanced Raman scattering (SERS), and optical trapping. / The first design is based on a coupling system involving double-layered metal nano-strips arrays. This system has the advantages of simple geometry and direct integration with microfluidic chips. The intense optical localization due to field coupling within the system can enhance detection sensitivity of target molecules, especially by virtue of the optical trapping of plasmonic nanoparticles. The optical resonant condition is obtained theoretically through analyzing the SPs modes. Numerical modeling based on two-dimensional (2D) finite-difference time-domain (FDTD) is consistent with the theoretical analysis and demonstrates the feasibility of using this system for optical sensing and trapping. Simulation results show that the refractive index sensitivity can reach ~200 nm/RIU, and a maximum SERS enhancement factor (EF) of 10⁹-10¹° is possible because of the near-field modulation and enhancement from optically trapped metal nanoparticles. / In the second design, a gold nano-ring structure is demonstrated to be an effective approach for plasmonic nano-optical tweezers (PNOTs) for trapping metallic nanoparticles. The plasmonic nano-ring structure has many interesting merits such as polarization insensitivity, wide tunable resonance range, uniform field enhancement around and inside the ring cavity, and ease of fabrication. This design has a unique feature of having large active volume for trapping. In our demonstration example, we have optimized a device for SERS operation at the wavelength of 785 nm. Three-dimensional (3D) FDTD techniques have been employed to calculate the optical response, and the optical force distribution have been derived using the Maxwell stress tensor (MST) method. Simulation results indicate that the nano-ring produces a maximum trapping potential well of ~32 kgT on a 20 nm gold nanoparticle. The existence of multiple potential well results in a very large active trapping volume of ~10⁶ nm³ for the target particles. Furthermore, the trapped gold nanoparticles further lead to the formation of nano-gaps that offer a near-field enhancement of ~160 times, resulting in an achievable EF of 10⁸ for SERS. / In the third design, we propose a concept of all-optical nano-manipulation. We show that target molecules, after being trapped, can be transferred between the trapping sites within a linear array of PNOTs. The system consists of an array of graded plasmonic nano-disks (NDs) with individual elements coded with different resonant wavelengths according to their dimensions. Thus, by switching the wavelength and rotating the polarization of the excitation source, the target nanoparticles trapped by the device can be manipulated from one ND to another. 3D FDTD simulation and MST calculation are utilized to demonstrate the operation of this idea. Our results reveal that the target experiences a trapping potential strength as high as 5000 kgT/W/μm², maximum optical torque of ~336 pN·nm/W/μm², and the total active volume may reach ~10⁶ nm³. The potential applications in terms of optical sensing are also discussed. / In the final design, for which experimental demonstration has been conducted, we show that PNOTs are achievable with random plasmonic nano-islands. Operation of the random PNOTs can be monitored by measuring the SERS enhancement factor in real time. Two laser beams having wavelengths of 633 nm and 785 nm are utilized to stimulate the PNOTs and excite the Raman signals simultaneously. The PNOTs are formed by annealing of a thermal evaporated gold film. This so-called nano-island substrate (Au-NIS) has a resonant peak close to 633 nm. The target is photochemical synthesized silver nanodecadedrons (AgNDs) functionalized with 4-Mercaptobenzoic acid (4-MBA) and the resonant peak of these AgNDs is far away from 633 nm and 785 nm. As the target is trapped to the hot-spots when the PNOTs are active, the near-field intensity is enhanced significantly, which results in the emergence of SERS signals, i.e. confirming the expected outcome of SERS upon nanotrapping by the PNOTs. This process is also elucidated numerically through 3D FDTD simulation and MST calculation. Furthermore, the target can be released as the PNOTs become inactive, i.e. disappearance of the SERS signal. Therefore, this design offers not only a robust avenue for monitoring trapping events in PNOTs, but also a reproducible “trap-and-sense“ platform for bio-detection. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Kang, Zhiwen. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2013. / Includes bibliographical references (leaves 146-170). / Abstracts also in Chinese. / Abstract --- p.I / Acknowledgements --- p.VIII / List of Illustrations --- p.XIII / Chapter Chapter 1. --- Introduction --- p.1 / Chapter 1.1 --- Surface Plasmon Polaritons and Localized Surface Plasmons --- p.1 / Chapter 1.2 --- Relevant Applications Based on Surface Plasmons --- p.3 / Chapter 1.3 --- Plasmonic Nano-Optical Tweezers and Relevant Applications --- p.7 / Chapter 1.4 --- Literatures Review and Objectives of this Thesis --- p.12 / Chapter 1.5 --- Structure of this Thesis --- p.17 / Chapter Chapter 2. --- Research Methodologies --- p.20 / Chapter 2.1 --- Theoretical Background of Surface Plasmons --- p.20 / Chapter 2.2 --- Numerical Simulation Techniques for Studying Complex Nanostructures --- p.30 / Chapter 2.3 --- Optical Force Calculation with the Maxwell Stress Tensor Method --- p.38 / Chapter 2.4 --- Nanostructure Fabrication and Characterization --- p.40 / Chapter Chapter 3. --- Optical Sensing Based on Double-Layered Metal Nano-Strips --- p.43 / Chapter 3.1 --- Introduction --- p.43 / Chapter 3.2 --- Theoretical Model and Analysis --- p.46 / Chapter 3.3 --- Numerical Verification and Discussion --- p.50 / Chapter 3.4 --- Optical Sensing Evaluation --- p.54 / Chapter 3.5 --- Near-Field Modulation by Optically Trapped Metal Nanoparticles --- p.58 / Chapter 3.6 --- Discussion --- p.61 / Chapter 3.7 --- Conclusion --- p.62 / Chapter Chapter 4. --- Gold Nano-Ring as Plasmonic Nano-Optical Tweezer --- p.64 / Chapter 4.1 --- Introduction --- p.64 / Chapter 4.2 --- Design and Optical Response --- p.67 / Chapter 4.3 --- Optical Force Calculation and Evaluation of Trapping Performance --- p.73 / Chapter 4.4 --- Stable Trapping Sites and Active Trapping Volume --- p.76 / Chapter 4.5 --- Near-Field Variation and Discussion --- p.81 / Chapter 4.6 --- Conclusion --- p.84 / Chapter Chapter 5. --- Graded Plasmonic Nano-Disks for Near-Field Nano-Manipulation --- p.86 / Chapter 5.1 --- Introduction --- p.86 / Chapter 5.2 --- Modeling and Optical Response --- p.89 / Chapter 5.3 --- Optical Force Distribution in the Structure --- p.91 / Chapter 5.4 --- Optical Trapping Potential and Rotational Energy --- p.96 / Chapter 5.5 --- Optical Trapping Volume and Discussion --- p.101 / Chapter 5.6 --- Conclusion --- p.104 / Chapter Chapter 6. --- Monitoring Plasmonic Nano-Optical Trapping through Detection of Surface-Enhanced Raman Scattering --- p.106 / Chapter 6.1 --- Introduction --- p.106 / Chapter 6.2 --- Numerical Investigation --- p.110 / Chapter 6.3 --- Sample Preparation and Characterization --- p.112 / Chapter 6.4 --- Experimental Implementation and Results --- p.122 / Chapter 6.5 --- Discussion --- p.134 / Chapter 6.6 --- Conclusion --- p.137 / Chapter Chapter 7. --- Conclusion and Outlook --- p.139 / References --- p.146 / Publications from this Work --- p.171