Zhuang, Junping = 單根納米線的軸向局域的光學性質 / 庄俊平. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references. / Abstracts in English and Chinese. / Zhuang, Junping = Dan gen na mi xian de zhu xiang ju yu de guang xue xing zhi / Zhuang Junping. / Acknowledgement --- p.I / Abstract --- p.II / 摘要 --- p.IV / Contents --- p.i / List of Figures --- p.iv / List of Tables --- p.viii / Abbreviations --- p.ix / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Background --- p.1 / Chapter 1.2 --- ZnSe Semiconductor Nanowires --- p.2 / Chapter 1.3 --- Carrier Dynamics in Semiconductor Nanowires --- p.3 / Chapter 1.3.1 --- Carrier Relaxation --- p.3 / Chapter 1.3.2 --- Surface Effects on Carrier Recombination --- p.7 / Chapter 1.4 --- Principle ofTCSPC Technique --- p.9 / Chapter 1.5 --- Motivations and Works --- p.10 / References --- p.12 / Chapter Chapter 2 --- Experiments --- p.17 / Chapter 2.1 --- Growth of ZnSe Nanowires --- p.17 / Chapter 2.2 --- Measurements with Electron Microscopes --- p.17 / Chapter 2.3 --- Measurements by a Laser Scanning Microscope --- p.18 / Chapter 2.3.1 --- Experimental Setup --- p.18 / Chapter 2.3.2 --- Settings of Measurements --- p.23 / References --- p.25 / Chapter Chapter 3 --- Methods of Analysis --- p.26 / Chapter 3.1 --- Luminescence Intensity --- p.26 / Chapter 3.1.1 --- Intensity Detected by PMT --- p.27 / Chapter 3.1.2 --- Intensity Detected by SPAD --- p.28 / Chapter 3.2 --- Lifetime Histogram --- p.29 / Chapter 3.2.1 --- Pixel Binning --- p.29 / Chapter 3.2.2 --- Lifetime Fitting --- p.32 / References --- p.33 / Chapter Chapter 4 --- Results and Discussion --- p.34 / Chapter 4.1 --- "Morphology, Structure and Composition of As-Grown Nanowires" --- p.34 / Chapter 4.2 --- Cathodoluminescence of Individual ZnSe Nanowires --- p.36 / Chapter 4.3 --- Photoluminescence of ZnSe Nanowires --- p.36 / Chapter 4.4 --- Luminescence of Individual Nanowires --- p.39 / Chapter 4.4.1 --- Luminescence of As-Grown Nanowires --- p.39 / Chapter 4.4.2 --- Nonlinear Optical Properties --- p.42 / Chapter 4.5 --- Luminescence Lifetimes of Individual Nanowires --- p.47 / Chapter 4.5.1 --- Power Dependence --- p.48 / Chapter 4.5.2 --- Chemical Environments --- p.53 / Chapter 4.5.3 --- Concentration of Ammonium Sulfide Solution --- p.56 / Chapter 4.6 --- Axially Resolved Luminescence Lifetimes --- p.60 / Chapter 4.6.1 --- Axially Resolved 2D Decay Diagrams --- p.60 / Chapter 4.6.2 --- Axially Resolved Luminescence Lifetimes --- p.62 / Chapter 4.6.3 --- (TNBE) and T1 of DL Emission --- p.69 / References --- p.72 / Chapter Chapter 5 --- Conclusions --- p.76 / Appendix A --- p.79 / Chapter A.1 --- Laser Beam Diameter and Spatial Resolution --- p.79 / Chapter A.2 --- Instrument Response Function of TCSPC module --- p.81 / Chapter A.3 --- Photo-Injection --- p.82 / Chapter A.3.1 --- Two-Photon Excitation by Pulse Laser --- p.82 / Chapter A.3.2 --- One-Photon Excitation by CW UV Laser --- p.84 / Chapter A.4 --- Lifetime Distributions --- p.85 / References --- p.86 / Appendix B Supporting Data --- p.87

Structural engineering plays an essential role in controlling the optical properties of nanostructures, which are of fundamental and practical interest in nanoscience and technology. In this study, two kinds of nanostructural engineering were investigated systematically to enrich nano-optics research: structural helicity was imposed on plasmonic nanoparticles (NPs) with chiroptical activity engineerable in the ultraviolet (UV)-visible region, and porosification was imposed on silicon nanowires (SiNWs) to tune optical interaction and photoluminescence (PL).. The generation of helical metamaterials, which have strong, engineerable chiroptical activity in the UV-visible region, has attracted increasing attention due to the manipulation of the circular polarization state of light to develop diverse homochirality-associated bio-applications. Glancing-angle deposition with fast substrate rotation is performed to generate plasmonic helical NPs (PhNPs) with a helical pitch (P) of less than 10 nm, which is so much smaller than the wire diameter (d) that the PhNPs appear to be achiral NPs. The PhNPs exhibit chiroptical activity that originates intrinsically from hidden helicity, characterized by circular dichroism (CD). With an increase of P from 3 to 66 nm, the plasmonic CD signals barely shift but show a logarithmic amplification. PhNPs made of aluminum, silver, and copper exhibit a stable chiroptical response from the deep UV (~220 nm) region to the visible region. When an achiral plasmonic nanostructure guest is coated on a PhNP host (i.e., a chiral host@achiral guest nanostructure is created), the achiral guest becomes chiroptically active due to helicity transfer from the chiral host to the achiral guest. Such a helicity transfer can be generally adapted to diverse plasmonic metals to tailor the plasmonic chiroptical response flexibly in the UV-visible region. Furthermore, an amplification of the near-field optical chirality induced by the PhNPs would pave a novel way to performing asymmetric syntheses, for which investigations are currently lacking. Silver PhNPs are used to effectively mediate the enantioselective photocyclodimerization of 2-anthracenecarboxylate: left-handed silver PhNPs lead to a positive ee (enantiomeric excess) value, and right-handed silver PhNPs give rise to a negative ee value. The enantioselectivity is enhanced with a decreasing P. The PhNP-mediated enantioselective photocyclodimerization is ascribed to the synergistic contribution from chirally helical surface-induced enantioselective adsorption of 2-anthracenecarboxylate and chiroptically active nanoplasmon-enhanced optical chirality of near-field circularly polarized light.. Metal-assisted chemical etching (MACE) is carried out to generate mesoporous SiNWs (mp-SiNWs) with mesopores from 2 to 50 nm. The porosification imposes two prominent properties onto SiNWs: a high surface-to-volume ratio and quantum confinement ascribed to the shrinkage of silicon skeletons. Hence, engineering the porosity of SiNWs is of fundamental importance. Here, a new method is devised to reduce the porosity of mp-SiNWs without changes in the MACE conditions. After generating the mp-SiNWs with high porosity, the mp-SiNWs are removed from the mother Si wafers with sticky tape, followed by MACE under the same conditions to produce low-porosity mp-SiNWs. Less porous mp-SiNWs reduce optical scattering from the porous Si skeletons and vertically protrude on the wafer without aggregation to facilitate optical trapping. Consequently, low-porosity mp-SiNWs effectively reduce UV-visible reflection loss. Furthermore, optical applications require surface modification of mp-SiNWs with functional chemicals, which has a prerequisite to passivate mp-SiNWs with H-termination using 5% hydrogen fluoride. 40% NH4F, which has been widely used to passivate Si(111) wafers with H-termination, tends to unexpectedly etch mp-SiNWs attributed to surface F-termination caused by the nucleophilic attack of F− anions to Si atoms. It has been used to study systematically the NH4F-etching rate as a function of the doping levels of SiNWs, surface crystalline orientations, and porosity. At a modest temperature of 110°C, 1,4-diethynylbenzene (DEBZ) is grafted via monosilylation grafted on H-terminated mp-SiNWs. The modified mp-SiNWs with chemically active monolayers is facilely subjected to further chemical modification and surface functionalization. In addition, the monosilylation encodes mp-SiNWs with PL of DEBZ, opening a door to flexible engineering of PL of mp-SiNWs for optoelectronic and bio-detection applications.

Orientador: Fernando Iikawa / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-08-14T10:28:22Z (GMT). No. of bitstreams: 1 Gadret_EvertonGeiger_M.pdf: 38585296 bytes, checksum: 3da598e65313d603b738c440498d2858 (MD5) Previous issue date: 2009 / Resumo: Neste trabalho foram estudadas as propriedades ópticas de nanofios de InP crescidos pelo método Vapor-Liquid-Solid (VLS) no sistema Chemical Beam Epitaxy (CBE) através da técnica de micro-fotoluminescência variando parâmetros de medida, tais como potência de excitação, polarização do sinal emitido e temperatura da amostra. Devido à formação de politipismo (InP nas fases cúbica, do tipo blenda de zinco (ZB), e hexagonal, do tipo wurtzita (WZ)) esta estrutura se torna interessante sob o ponto de vista das propriedades ópticas, devido às interfaces InP¿ZB/InP¿WZ do tipo II. Notamos que há poucas informações na literatura a respeito da estrutura eletrônica do InP na fase wurtzita porque esta fase só foi relatada em nanofios. Concentramos, assim, nossa investigação sobre a estrutura eletrônica de nanofios que contenham ambas as fases. Identificamos emissões ópticas dos poços quânticos tipo II em nanofios de InP assim como emissões envolvendo impurezas aceitadoras rasas e recombinação no gap do InP¿WZ. A emissão óptica dos poços quânticos tipo II é dominante a baixas temperaturas, abaixo de 100K, e está entre 1,44 e 1,46eV a 10K. O comportamento desta emissão como função da temperatura, potência de excitação e polarização da luz está de acordo com a estrutura proposta e é confirmada por imagem de microscopia eletrônica de transmissão (TEM). A emissão óptica da impureza rasa está ~ 43meV abaixo da emissão do poço quântico, valor bem próximo do carbono aceitador no InP na fase cúbica. A emissão óptica associada ao InP¿WZ em 1,49eV (10K) foi observada a temperaturas de 10K a 300K, em concordância com resultados relatados na literatura. Observamos também transição óptica relacionada a portadores localizados nas barreiras dos poços quânticos a temperaturas mais altas, acima de 150K. / Abstract: Optical properties of InP nanowires grown by Vapor-Liquid-Solid (VLS) method in a Chemical Beam Epitaxy system were investigated by using micro-photoluminescence spectroscopy varying experimental parameters such as excitation power, emitted signal polarization and sample temperature. Due to polytypism (InP in cubic, zincblende (ZB), and hexagonal, wurtzite (WZ) phases), this structure becomes interesting by the point of view of optical properties, due to type¿II InP¿ZB/InP¿WZ interfaces. We have noticed that there are few informations in the literature about electronic structures of InP in wurtzite phase, because this phase has been only reported in nanowires. We focused, thus, our investigation about electronic structure of nanowires having both structural phases. We identified optical emissions from type II quantum wells in InP nanowires as well as emissions involving shallow acceptor impurities and InP¿WZ gap recombination. The type II quantum well optical emission is dominant at low temperatures, below 100K, which is in 1,44 ¿ 1,46eV range at 10K. This emission behavior as function of temperature, excitation power and light polarization is in agreement with the proposed structure and is supported by transmission electronic microscopy (TEM) imagem. The shallow impurity emission is ~ 43meV below the quantum well emission, a value close to the carbon acceptor in InP in cubic phase. The optical emission associated to the InP¿WZ at 1,49eV (10K) was observed from temperatures of 10K to 300K, in agreement with results reported in literature. We also observed an additional optical transition related to the carrier localized at the barriers of the quantum wells at at high temperatures, above 150K. / Mestrado / Física da Matéria Condensada / Mestre em Física