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Saj, Damian, and Izabela Saj. "Nanowire-based InP solar cell materials." Thesis, Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE), 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-19455.
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In this project, a new type of InP solar cell was investigated. The main idea is that light is converted to electrical current in p-i-n photodiodes formed in thin InP semiconductor nanowires epitaxially grown on an InP substrate. Two different types of samples were investigated. In the first sample type (series C03), the substrate was used as a common p-type electrode, whereas a short p-segment was included in all nanowires for the second sample type (B07). Current – voltage (I-V) characteristics with and without illumination were measured, as well as spectrally resolved photocurrents with and without bias. The main conclusion is that the p-i-n devices showed good rectifying behavior with an onset in photocurrent that agrees with the corresponding energy band gap of InP. An interesting observation was that in series B07 (with included p-segments) the photocurrent was determined by the band gap of hexagonal Wurtzite crystal structure, whereas series C03 (without p-segments) displayed a photocurrent dominated by the InP substrate which has a Zincblende crystal structure. We found that the overall short-circuit current was ten as large for the latter sample, stressing the importance of the substrate as a source of photocurrent.
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Anufriev, Roman. "Optical properties of InAs/InP nanowire heterostructures." Thesis, Lyon, INSA, 2013. http://www.theses.fr/2013ISAL0133/document.
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Ce travail de thèse porte sur l’étude des propriétés optiques de nanofils InP et d’hétérostructures nanofils InAs/InP épitaxiés sur substrat silicium. Ce travail de thèse a été réalisé principalement dans le cadre du projet ANR «INSCOOP»This thesis is focused upon the experimental investigation of optical properties of InAs/InP NW heterostructures by means of photoluminescence (PL) spectroscopy. First, it was demonstrated that the host-substrate may have significant impacts on the optical properties of pure InP NWs, as due to the strain, created by the difference in the LTECs of the NWs and the host-substrate, as due to some other surface effects. Next, the optical properties of such nanowire heterostructures as quantum rod (QRod) and radial quantum well (QWell) NWs were investigated. The features of obtained spectra were explained using theoretical simulation of similar NW heterostructures. The polarization properties of single InP NWs, InAs/InP QWell-NWs, InAs/InP QRod-NWs and ensemble of the InAs well ordered NWs were studied at different temperatures. Further, we report on the evidences of the strain-induced piezoelectric field in WZ InAs/InP QRod-NWs. Finally, PL QE of NW heterostructures and their planar analogues are measured by means of a PL setup coupled to an integrating sphere. In general, the obtained knowledge of the optical and mechanical properties of pure InP NWs and InAs/InP NW heterostructures will improve understanding of the electrical and mechanical processes taking place in semiconductor NW heterostructures and will serve for the fabrication of future nanodevice applications
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Hajji, Maryam. "A comparative study of Nanowire-based InP and Planar ITO/InP Photodetectors." Thesis, Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE), 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-15589.
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Photodetectors are a kind of semiconductor devices that convert incoming light to an electrical signal. Photodetectors have different applications in sensors and fiber optic communication systems, and medical diagnosis etc. In this project Fourier Transform Infrared (FTIR) Spectroscopy is used to investigate a new version of photodiodes for near-infrared radiation that is based on self-assembled semiconductor nanowires (NWs) which are grown directly on the substrate without any epi-layer. The spectrally resolved photocurrent (at different applied biases) and IV curves (in darkness and illumination) for different temperatures have been studied, respectively. The thesis work also includes a comparison to a planar photodetector based on Indium Tin Oxide (ITO) deposited directly on an InP substrate.
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MALEKRAH, MEHDI. "Electrical and Optical Charactristics of InP Nanowire Photodetectors." Thesis, Halmstad University, MPE-lab, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-4835.
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In this project Fourier Transform Infrared Spectroscopy is used to investigate a new kind of photodiode that is based on nanowires. The photo current and I-V curves for different temperatures, different applied biases, in darkness and illumination condition have been studied. The experiment was conducted in the temperature range from 78 K (-195ºC) to 300 K (27ºC). These photo diodes are designed to work on NIR wavelengths. The results show some excellent properties, such as high break down voltage, and that is an important advantage for photo detectors, low and constant reverse saturation current (Is). The results show some defects, most of them come from fabrication. The design of the sample is also discussed.
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Ngo, Tuan Nghia, and Irina Zubritskaya. "Electrical and Optical Characterization of InP Nanowire Ensemble Photodetectors." Thesis, Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE), 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-17457.
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Photodetectors are semiconductor devices that can convert optical signals into electrical signals. There is a wide range of photodetector applications such as fiber optics communication, infrared heat camera sensors, as well as in equipment used for medical and military purposes. Nanowires are thin needle-shaped structures made of semiconductor materials, e.g. gallium arsenide (GaAs), indium phosphide (InP) or silicon (Si). Their small size, well-controlled crystal structure and composition as well as the possibility to fabricate them monolithically on silicon make them ideally suited for sensitive photodetectors with low noise. In this project, Fourier Transform Infrared (FTIR) Spectroscopy is used to investigate the optical characteristics of InP nanowire-based PIN photodetectors. The corresponding electrical characteristics are also measured using very sensitive instrumentation. A total of 4 samples consisting of processed nanowires with 80 nm diameter but different density and length have been examined. The experiments were conducted from 78K (-196oC) to room temperature 300K (27oC). The spectrally resolved photocurrent and current-voltage (IV) curves (in darkness & under illumination) for different temperatures have been studied and analyzed. The samples show excellent IV performance with very low leakage currents. The photocurrent scales with the number of nanowires, from which we conclude that most photocurrent is generated in the substrate. Spectrally resolved photocurrent data, recorded at different temperatures, display strong absorption in the near-infrared region with interesting peaks that reveal the underlying optical processes in the substrate and nanowires, respectively. The nature of the absorption peaks is discussed in detail. This study is an important step towards integration of optically efficient III-V nanoscale devices on cheap silicon substrates for applications e.g. on-chip optical communication and solar cells for energy harvesting.
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Dawei, Jiang. "Electrical and optical characterization of InP nanowire-based photodetectors." Thesis, Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-25733.
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This thesis deals with electrical and optical characterization of p+i–n+ nanowire-based photodetectors/solar cells. I have investigated their I-V performance and found that all of them exhibit a clear rectifying behavior with an ideality factor around 2.2 at 300K. used Fourier transform infrared spectroscopy to extract their optical properties. From the spectrally resolved photocurrent data, I conclude that the main photocurrent is generated in the i-segment of the nanowire (NW) p-i-n junctions, with negligible contribution from the substrate. I also used a C-V technique to investigate the impurity/doping profiles of the NW p+-i-n+ junction. The technique has been widely used for investigations of doping profiles in planar p-n junctions, in particular with one terminal (n or p) highly doped. To verify the accuracy of the technique, I also used a planar Schottky sample with an already known doping profile for a test experiment. The result is very similar to the actual data. When we used the technique to investigate the doping level in the NWs photodetectors grown on InP substrates, the results show a very high capacitance above 800pF which most likely is due to the influence of the parasitic capacitance from the insulating layer of SiO2. Thus, a new sample design is required to investigate the doping profiles of NWs.
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Amin, Mohammed, and Md Obaidul Alam. "Electrical and optical characteristics of InP interband nanowire infrared photodetectors." Thesis, Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE), 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-6219.
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We have investigated two devices for detection of radiation, typically in the infrared range, Photons are absorbed in an active region of semiconductor devices such that the absorption induces inter band electronic transitions and generate photo-excited charge carriers. A photocurrent is generated between the conducting contacts through the active region of the devices. We worked on infrared photodectors based on nanowires. This type of photodectors can be used for optical communication and to detect atmospheric pollution by absorption of the polluting molecules in the infrared region (0.7µm-1µm). In this project we have used Fourier transform infrared spectroscopy to study and compared the photoresponse of two different types of interband nanowire infrared photodetectors 8samples 6080 and 6074). Fourier Transform infrared (FTIR) spectroscopy is a measurement technique that allows one to record infrared spectra in all wavelengths at then same time. The basic task was to compare and analyse the electrical and optical characteristics of these two detectors at different temperatures (78K-300K) corresponding to the wavelength.
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Zhao, Guiping. "Fabrication and characterization of nanowire arrays on InP(100) surfaces." Thesis, University of Newcastle Upon Tyne, 2007. http://hdl.handle.net/10443/964.
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This work investigates the technique of mass fabrication of nanowires on semiconductor InP (100) surfaces by low energy Ar+ ion beam bombardment. Systematic investigation shows that under some crucial experimental parameters, nanowire arrays of regular periodicity can be produced. An ambient Atomic Force Microscope was used in contact mode to examine the morphology of the irradiated InP surfaces. The chemical composition of the irradiated samples was characterized by X-ray Photoelectron Spectroscopy (XPS). The electronic structure of the fabricated nanowire arrays was jointly explored by Scanning Tunnelling Spectroscopy and XPS. The research shows that In enriched ripples and nanowires form under prolonged irradiation by Ar+ ions due to preferential sputtering of P from InP under grazing ion incident angle above some crucial irradiation ion dose. A model of mergence from tailed cones is proposed to account for the formation of these ripples and nanowires. The drive to the formation of periodic ripples and nanowires is believed to be stress-field induced self-organisation of strained cones. The cone-mergence model is a combination of the model of stress-field induced self-organization and the model of ripple topography by Bradley and Harper (BH). The research proposes that the mobility of atoms on the corresponding solid surfaces under ion bombardment decides whether the surface morphology is generated by the stress-field, the BH, or a combination of the two models. Monte-Carlo simulation was used to evaluate the effect of surface damage and preferential sputtering of P from InP and N from Si3N4. The calculations predict that P and N can be preferentially sputtered from InP and Si3N4 surfaces.
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Singaravelu, Praveen Kumar, and Tawhidul Alam Mohammad. "Electrical and Optical Characterization of InAsP/InP Nanowire-Based Avalanche Photodetectors." Thesis, Högskolan i Halmstad, Fotonik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-30144.
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The availability of new manufacturing methodology in solid state physics makes it possible to grow nano-photonic devices for better performance and unique properties. In this thesis work, we use I-V and FTIR spectroscopy to study the electrical and optical properties of InAsP/InP nanowire-based array avalanche photodetectors for near infrared applications. Measurements are performed at 300K and 5K for different applied biases under darkness and illumination conditions. I-V curves are plotted to understand the charge carrier transport in nanowire photodetectors and also to improve the device fabrication. I-V characteristics display non-optimal diode properties with large dark leakage currents. From spectrally resolved photocurrent measurements, peaks appear at photon energies of 1.34eV and 1.4eV respectively, corresponding to the bandgap of zinc blende (ZB) and wurtzite (WZ) InP. An additional photocurrent peak at 1.25eV agrees with the bandgap of the included InAsP segments. The Schottky-like contacts present at the top of the nanowires most likely generate additional photocurrent at higher photon energies. No breakdown effect is observed for the array devices. Complementary single-nanowire devices indicate an avalanche breakdown effect at VR=-35V.
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Raval, Divya. "I-V and Optical Characterization of InP/InAsP Quantum Disc-in-Nanowire Infrared Photodetectors." Thesis, Högskolan i Halmstad, Akademin för informationsteknologi, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-40162.
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Photodetectors are semiconductor devices capable of converting optical signals into electrical signals. There is a wide range of applications for photodetectors such as fiber optics communication, infrared heat camera sensors, as well as in medical and military equipment.Nanowires are thin needle-shaped structures consisting of semiconductor materials such as gallium arsenide (GaAs), indium phosphide (InP) or silicon (Si). They are ideally suited for sensitive photodetectors with low noise due to their small size, well-controlled crystal structure, and composition tunability, as well as the possibility to fabricate them monolithically on silicon.In this thesis, Fourier Transform Infrared (FTIR) Spectroscopy was used to investigate the optical characteristics of InP nanowire-based n+-i-n+ photodetectors with 20 embedded InAsP quantum discs in each InP nanowire. The spectrally resolved photocurrent was measured and analyzed at different angles of incidence. Also, detailed current-voltage characteristics in dark and under illumination were recorded and analyzed.Summarized, the samples showed very good I-V performance with low dark leakage currents. The photocurrent scales with the numbers of nanowires, from which we conclude that most of the photocurrent is generated in the nanowires. Spectrally resolved photocurrent data, recorded at room-temperature, shows strong absorption in the near-infrared region with interesting peaks that reveal, the underlying optical processes in the substrate and nanowires.
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Kaveh, Baghbadorani Masoud. "Emission and Dynamics of Charge Carriers in Uncoated and Organic/Metal Coated Semiconductor Nanowires." University of Cincinnati / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1470754655.
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Mansouri, Ebrahim. "Studies on Radiation-induced Defects in InP/InAsP Nanowire-based Quantum Disc-in wire Photodetectors." Thesis, Högskolan i Halmstad, Akademin för informationsteknologi, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-36126.
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Photodetectors are used in many applications such as digital and thermal cameras or in solar panels. They can also be designed to detect the omnipresent high-energy radiation/particles, and for radiation imaging in biomedical applications. Novel nanostructures offer significant advantages compared to traditional designs for the realization of fast, sensitive, compact and cheap sensors and efficient solar cells. Examples of such nanostructures include quantum dots (QDs), quantum wells (QWs) and NW arrays. This thesis is devoted to experimental investigations of effects of high-energy (1 MeV) protons on the optical and electrical performance of InP/InAsP NW-based QDiscs-in wire photodetectors. The proton-induced degradation of the optical performance has been studied by means of Fourier Transform Infrared (FTIR) photocurrent spectroscopy. The spectrally resolved photocurrent (PC) and current-voltage (I-V) characteristics were measured at low temperature (5 K and 77K) and at room temperature (300K) before and after 1 MeV proton irradiation under vacuum conditions with fluences ranging from 1.0×1012–3.0×1013 cm-2. The particle radiation exposure has been done in the Ion Beam Accelerator at the Department of Nuclear Physics Department at Lund University. Considering both PC and I-V characteristics, it was found that the devices were sensitive to all proton irradiation at all fluences. In general, the PC intensity significantly increased after radiation for all fluences, however, a week after exposure the PC and dark current gradually recovered. At 3×1012 p/cm2 fluence level, it was figured out that photocurrent which attributed to QDiscs disappeared for a couple of days after exposure, however, over time and gradually, those started to manifest again even at low and room temperatures, causing radiation-induced changes in device parameters to be time-dependent; however, it was not recorded any signals related to QDiscs at fluence of 3×1013 p/cm2. Substantial changes in the dark I-V characteristics, as well as increases in the dark current, are observed after irradiation. The influence of proton irradiation on light and dark current characteristics also indicated that NW structures are a good potential candidate for radiation harsh-environment applications. It was also observed a significant increase in dark current after the radiation for all devices, however, by applying the voltage to the photodetectors, the PC and I-V characteristics gradually being to diminish, which may be attributed to an annealing process.
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Alber, Ina [Verfasser], and Reinhard [Akademischer Betreuer] Neumann. "Synthesis and Plasmonic Properties of Metallic Nanowires and Nanowire Dimers / Ina Alber ; Betreuer: Reinhard Neumann." Heidelberg : Universitätsbibliothek Heidelberg, 2012. http://d-nb.info/1177039982/34.
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Campos, Tiago de. "Nanowires de InP: cálculo do espectro de absorção via método k.p." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/76/76132/tde-25092013-092712/.
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Nos últimos anos, os avanços nas técnicas de crescimento de semicondutores permitiram a fabricação de nanoestruturas isoladas de alta qualidade e com confinamento radial. Essas estruturas quase unidimensionais, conhecidas como nanowires (NWs) têm aplicações tecnológicas vastas, tais como nano sensores químicos e biológicos, foto-detectores e lasers. Seu uso em aplicações tecnológicas requer a compreensão de características óticas e eletrônicas e um estudo teórico mais profundo se faz necessário. O objetivo desse estudo e calcular teoricamente o poder de absorção para NWs de InP e comparar os resultados para as fases cristalinas zincblende (ZB) e wurtzita (WZ) nas suas direções de crescimento equivalentes. Usamos neste estudo a formulação do método k.p que descreve as duas fases cristalinas em um mesmo Hamiltoniano, a aproximação da função envelope e a expansão em ondas planas. O poder de absorção foi calculado a partir das transições entre as bandas de valência e condução através da regra de ouro de Fermi. Mesmo o método k.p sendo o menos custoso computacionalmente, quando comparado com seus correspondentes ab initio, o tamanho das matrizes envolvidas nos cálculos pode ultrapassar a barreira dos giga elementos. Para lidar com essas matrizes, foi implementado um método de resolução de sistemas lineares iterativo, o LOBPCG, utilizando o poder de processamento disponível nas placas gráficas atuais. O novo modo de resolução apresentou ganhos consideráveis em relação ao desempenho observado com os métodos de diagonalização diretos em testes com confinamento em uma única direção. A falta de um pré-condicionador adequado limita o seu uso em NWs. Os cálculos de absorção para NWs na fase ZB apresentaram uma anisotropia em seu espectro de absorção de mais de 90%, enquanto os na fase WZ apresentaram dois regimes distintos de anisotropia, governados pelo aparecimento de um estado oticamente proibido no topo da banda de valência. Em suma, os resultados obtidos com o modelo teórico proposto nesse estudo apresentam as propriedades óticas reportadas na literatura, inclusive o estado oticamente proibido observado em outros sistemas na fase WZ com um alto confinamento quântico.In recent years, the advances of growth techniques allowed the fabrication of high quality single nanostructures with quantum confinement along lateral directions. These quasi one-dimensional structures known as nanowires (NWs) have vasts technological applications, such as biological and chemical nanosensors, photo detectors and lasers. The applications involving NWs require the comprehension of their optical and electronic properties and, therefore, a deep theoretical understanding should be pursued. The aim of this study is to provide optical absorption theoretical calculations for InP NWs, comparing the results for zincblende (ZB) and wurtzite (WZ) crystal phases, in their equivalent growth directions. We use the k.p method formulation that allow the description of both structures with the same Hamiltonian, the envelope function approximation and the plane wave expansion. The absorption power was calculated for transitions between valence and conduction bands using Fermis Golden Rule. Although the k.p method demands less computational effort, when compared to ab initio calculations, the k.p matrices can break the giga elements barrier. To deal with these matrices, we implemented an linear system solver method, the LOBPCG, using the processing power available in current GPUs. The new resolution method showed a considerable gain comparing the performance of direct diagonalization methods, when tested in systems with confinement in one direction. The lack of an adequate preconditioner limits its use in NWs. The absorption spectra calculations for ZB NWs presented a 90% plus anisotropy, whilst WZ NWs have two distinct regimes, ruled by the presence of an optically forbidden state at valence band maximum. In summary, the results obtained with the theoretical model in this study are in great agreement with optical properties reported in the literature, including the optically forbidden state observed in other WZ systems with high quantum confinement.
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Gadret, Everton Geiger. "Propriedades ópticas de nanofios de InP." [s.n.], 2009. http://repositorio.unicamp.br/jspui/handle/REPOSIP/277740.
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Orientador: Fernando IikawaDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin
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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
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Maharjan, Amir M. "Investigation of single InP nanowires and CdS nanosheets by using photocurrent and transport spectroscopy." Cincinnati, Ohio : University of Cincinnati, 2009. http://rave.ohiolink.edu/etdc/view.cgi?acc_num=ucin1258658812.
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Thesis (Ph.D.)--University of Cincinnati, 2009.Advisor: Andrei Kogan. Title from electronic thesis title page (viewed Jan. 19, 2010). Keywords: photocurrent spectroscopy; transport spectroscopy; InP nanowires; photocurrent; CdS nanowires. Includes abstract. Includes bibliographical references.
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Ahmed, Rizwan, and Shahid Abbas. "Electrical and Optical Characteristics of InP Nanowires based p-i-n Photodetectors." Thesis, Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE), 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-13915.
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Photodetectors are a kind of semiconductor devices that convert incoming light to an electrical signal. Photodetectors are classified based on their different structure, fabrication technology, applications and different sensitivity. Infrared photodetectors are widely used in many applications such as night vision, thermal cameras, remote temperature sensing, and medical diagnosis etc. All detectors have material inside that is sensitive to incoming light. It will absorb the photons and, if the incoming photons have enough energy, electrons will be excited to higher energy levels and if these electrons are free to move, under the effect of an external electric field, a photocurrent is generated. In this project Fourier Transform Infrared (FT-IR) Spectroscopy is used to investigate a new kind of photodiodes that are based on self-assembled semiconductor nanowires (NWs) which are grown directly on the substrate without any epi-layer. The spectrally resolved photocurrent (at different applied biases) and IV curves (in darkness and illumination) for different temperatures have been studied respectively. Polarization effects (at low and high Temperatures) have been investigated. The experiments are conducted for different samples with high concentration of NWs as well as with lower concentration of NWs in the temperature range from 78 K (-195ºC) to 300 (27ºC). These photodiodes are designed to work in near infrared (NIR) spectral range. The results show that the NW photodetectors indeed are promising devices with fairly high break down voltage, change of photocurrent spectra with polarized light, low and constant reverse saturation current (Is). The impact of different polarized light on photocurrent spectra has been investigated and an attempt has been made to clarify the observed double peak of InP photocurrent spectrum. Our investigations also include a comparison to a conventional planar InP p-i-n photodetector.
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Novotny, Clint Joseph. "A study of InP nanowires growth, material properties, and application in optoelectronics /." Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2007. http://wwwlib.umi.com/cr/ucsd/fullcit?p3283560.
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Thesis (Ph. D.)--University of California, San Diego, 2007.Title from first page of PDF file (viewed November 21, 2007). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references.
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Miranda, La Hera Vladimir Roger 1988. "Optical properties of wurzite phase InAsP/InP heterostructure nanowires=Propriedades ópticas de nanofios de InAsP/InP heteroestruturados na fase wurzita." [s.n.], 2015. http://repositorio.unicamp.br/jspui/handle/REPOSIP/276911.
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Orientadores: Fernando Iikawa, Odilon Divino Damasceno Couto JuniorDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin
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Resumo: Neste trabalho foram estudadas as propriedades ópticas de nanofios (NWs) semicondutores InAsP/InP na fase Wurzita, crescidos pelo método Vapor-Liquid-Solid (VLS) no sistema Chemical Beam Epitaxy (CBE). As medidas ópticas foram realizadas por espectroscopia de fotoluminescência em ensembles e nanofios individuais, por macro e micro-fotoluminescência. O interesse pelas ligas de InAsP é que elas apresentam energia do gap na faixa de infravermelho próximo, uma faixa espectral utilizada para a tecnologia de telecomunicações bem como em fabricação de detetores de compostos de carbono nocivos, pois eles apresentam absorção óptica nessa faixa. Além disso, InAsP na forma de estruturas na escala nanométrica, em particular, em NWs, além de ter a fase cúbica estável, que ocorre em todos os fosfetos e arsenetos de compostos III-V, a fase hexagonal wurtzita é também observada. A maioria de suas propriedades na estrutura wurtzita não ainda foi investigada em detalhes. Os nanofios heteroestruturados contendo InAsP e InP na fase wurtzita não são bem conhecidos também. O ponto principal desta tese é, portanto, investigar as propriedades ópticas desses compostos na forma de nanofios, que estão na fase wurtzita, e estudar a emissão óptica destas heteroestruturas, onde envolve o efeito de confinamento quântico, o qual pode ser utilizado para sintonizar o comprimento de onda da emissão. Investigamos NWs de ligas de InAsP com três composições diferentes, mudando o fluxo de arsina e fosfina, que foram crescidos usando três tamanhos de nanopartículas de catalizadores de Au diferentes de 2, 5 e 20 nm. Observamos que a forma do nanofio depende do tamanho de nanopartículas de Au. Para menores tamanhos, obteve-se uma forma de torre, enquanto que para o maior, a forma de agulha. A concentração de P é de cerca de 50% estimada por espectroscopia de fotoluminescência e de energia dispersiva de raios-X. A emissão óptica é de cerca de 1.5 µm, adequada para aplicação em dispositivos de telecomunicações. Nos NWs heteroestruturados de InAsP/InP, investigamos as amostras com tempos de inclusão diferentes de InAsP (2, 5, 10, 20 e 40 s) no InP, e elas foram crescidas com diferentes tamanhos de nanopartículas de Au (2, 5 e 20 nm) utilizadas como catalisador. Nessas amostras, todos os nanofios apresentam a forma de uma agulha. Os espectros de macro e micro-fotoluminescência mostram fortes emissões ópticas atribuídas à camada de InAsP e variam entre 800-1000 nm. A energia de emissão depende da quantidade de InAsP de acordo com o efeito de confinamento quântico. Também, observamos várias linhas estreitas nos espectros de micro-fotoluminescência de nanofios individuais atribuídos aos estados localizados das camadas InAsP. Essas linhas são provenientes de duas regiões, sendo uma delas da camada de InAsP axial catalisado e uma segunda, da camada lateral de InAsP devido ao crescimento epitaxial. Este resultado mostra que os NWs de InAsP/InP apresentam alta qualidade cristalina e são sistemas promissores para a aplicação em dispositivos ópticos
Abstract: In this work, we studied the optical properties of wurtzite phase InAsP alloy nanowires (NWs) and InAsP/InP heterostructure nanowires grown by Vapor-Liquid-Solid (VLS) method in a Chemical Beam Epitaxy (CBE) system. The optical measurements were carried out by photoluminescence spectroscopy in ensemble and single NWs by macro and micro-photoluminescence techniques. The interest for InAsP alloys is that they present gap energy in the near infra-red, a spectral range commonly used for the telecommunication technology as well as for harmful carbon compounds detection sensors, since their optical absorption is in the same energy range. Furthermore, the InAsP in nanoscale structures, in particular, in NWs, in addition to the stable cubic phase, which occurs in all other phosphide and arsenide III-V compounds, hexagonal wurtzite phase is also observed. Most of the properties of their wurtzite structure has not been investigated in details yet. The heterostructure NWs containing InAsP and InP in wurtzite phase are not deeply known as well. The main purpose of this thesis is, therefore, to investigate the optical properties of this compounds in NW forms, which present wurtzite phase, and to study the optical emission from the heterostructures, where the quantum confinement effect can also be used to tune the emission wavelength. We investigated InAsP alloy NWs with three compositions changing the arsine and phosphine flux and they are grown using three sizes of Au-nanoparticle catalyst, 2, 5 and 20 nm. We note that the NW shape depends on the Au-nanoparticle size. For small size, a tower-like shape was observed, while for large one, the needle-like one. The P content of the samples is around the 50 % estimated by the photoluminescence and by Energy-Dispersive X-ray spectroscopy. The optical emission is around 1.5 µm, appropriate for telecommunication device applications. For InAsP/InP heterostructure NWs, we investigated samples with different InAsP time deposition (2, 5, 10, 20 and 40 s) onto the InP and they were grown with different Au-nanoparticle size (2, 5 and 20 nm) used as catalyst. In these samples, all nanowires present needle-like shape. The macro and micro-photoluminescence spectra show strong optical emissions in 800-1000 nm range attributed to the InAsP layer emissions. The emission energy depends on the amount of InAsP according to the quantum confinement effect. We observed several sharp lines in the micro-photoluminescence spectra of single NWs attributed to the localized states of the InAsP layers. They come from two regions, one of them from the axial catalyst InAsP layer and second one, from the lateral InAsP epitaxial growth layer. The result shows that the InAsP/InP heterostructures NWs grown by VLS method in the CBE system present high crystal quality and are promising structure for optical device applications
Mestrado
Física
Mestre em Física
1247651/2013
CAPES
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Perera, Saranga D. "Investigation of exciton dynamics and electronic band structure of InP and GaAs nanowires." University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1352993854.
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Colussi, Marcio Luiz. "Investigação teórica sobre possíveis aplicações na eletrônica de nanofios de AlN, GaN e InN: um estudo de primeiros princípios." Universidade Federal de Santa Maria, 2012. http://repositorio.ufsm.br/handle/1/3910.
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Coordenação de Aperfeiçoamento de Pessoal de Nível SuperiorUsing the formalism of Density Functional Theory with spin polarization and the Generalized Gradient Approximation for exchange and correlation term, we studied the stability and electronic properties of substitutional impurities of C, Si and Ge in GaN, AlN and InN nanowires and the variation of the band offset with the diameter variation in AlN/GaN nanowires heterojunctions. For the study of substitutional impurities we use AlN, GaN and InN nanowires in the wurtzite phase with diameter of 14.47 Å, 14.7 Å and 16.5 Å, respectively. For the study of variation of the band offset with the diameter of the nanostructure, we use nanowires in the wurtzite phase with a mean diameter ranging from 0.99 nm to 2.7 nm and the zinc blende phase with an average diameter ranging from 0.75 nm to 2.1 nm. The electronic structure calculations show that of GaN, AlN and InN nanowires are semiconductors with direct band gap at point Γ. To study the substitutional impurities, we consider that the impurity can occupy the cation or anion sites in non-equivalent positions that are distributed from the center to the surface of the nanowire. For the C impurities, in GaN nanowires, we find that when the C atom is substituted in the N site, it will be uniformly distributed along the diameter of the nanowire. When substituted at the Ga site, it will be preferably find on the surface of the nanowire. In this case, the formation energy of CGa is almost identical to the CN, thus can occur formation of the auto-compensed CN-CGa pair. In AlN nanowires, when the C atom occupying the N site, it is also observed an almost uniform distribution along the diameter of the nanowire with a small preference (less energy formation) to the surface sites. Since the formation energy of the CN is lower than CAl in all regions of the nanowires, taking thus more likely to form CN. For InN nanowires, in the center sites, the formation energy of the CN and CIn is very similar, and the CN will have a uniform distribution along the diameter, but on the surface of the CIn is more stable and band structure show that this configuration has shallow donor levels. For Ge substitutional impurities in GaN nanowires, we observed that the center of the nanowire, the Ge atom is more likely to be found located in the Ga site, but in surface to find the most likely of N site, this being the most stable configuration. For AlN nanowires, the center of nanowire is possible to find the Ge atom at the N or Al sites, as the formation energy is practically the same. On the surface the more likely it is to find the Ge atom of the N site, which also is the most stable configuration. As for InN nanowires, the Ge atom will be found preferably at the In site with uniform distribution along the diameter of the nanowire. Analyzing the band structure of GeIn observed shallow donor levels. For the Si substitutional impurities, we obtain that in GaN and InN nanowires of the most stable configuration, the Si atom is to be found at the cation (Ga and In) sites in the central sites of the nanowire and analyzing the band structure of SiGa and SiIn, we also observed shalow donor levels. However, for AlN nanowires in the centerof the nanowire is greater the probability of finding the Si atom at the Al site, but the surface is greater the probability of finding the Si atom at the N site which is the most stable configuration. Finally, we analyze the variation of the band offset to the change in diameter of the nanowires forming the heterostructure. We consider heterostructure on yhe wurtzite and zinc blende phases, therefore during the synthesis the two phases are obtained. We found that the result is similar for the two phases and the extent that the diameter increases the value of the band offset also increases, tending to the value obtained for the bulk.
Usando o formalismo da Teoria do Funcional da Densidade com polarização de spin e a aproximação do gradiente generalizado para o termo de troca e correlação, estudamos a estabilidade e as propriedades eletrônicas de impurezas substitucionais de C, Si e Ge em nanofios de GaN, AlN e InN e a variação do band offset com o diâmetro em heteroestruturas da nanofios AlN/GaN. Para o estudo de impurezas substitucionais utilizamos nanofios de AlN, GaN e InN na fase da wurtzita e com diâmetros de 14,47 Å, 14,7 Å e 16,5 Å, respectivamente. Já para o estudo da variação do band offset com o diâmetro da nanoestrutura, utilizamos nanofios que formam a heteroestrutura na fase wurtzita com diâmetro médio variando 0,99 nm até 2,7 nm e na fase blenda de zinco com diâmetro médio variando de 0,75 nm até 2,1 nm. Os cálculos de estrutura eletrônica apresentam que os nanofios de AlN, GaN e InN são semicondutores com gap direto no ponto Γ. Para o estudo das impurezas substitucionais, consideramos que a impureza pode ocupar o sítio do cátion ou do aniôn, em posições não equivalentes que estão distribuídas do centro até a superfície do nanofio. Para a impureza de C, em nanofios de GaN, obtemos que, quando o átomo de C for substituído no sítio do N, o mesmo vai estar distribuído uniformemente ao longo do diâmetro do nanofio. Já quando substituído no sítio do gálio, o mesmo vai ser encontrado preferencialmente na superfície do nanofio, sendo que, na superfície do nanofio a energia do formação do CGa é praticamente a mesma do CN, assim pode ocorre a formação de pares autocompensados CN-CGa. Em nanofios de AlN, quando o átomo de C ocupar o sítio do N, também vai ter uma distribuição quase uniforme ao longo do diâmetro do nanofio com uma pequena preferência (menor energia de formação) para os sítios da superfície. Sendo que a energia de formação do CN é menor que do CAl em todas as regiões do nanofios, tendo assim, probabilidade maior de formar CN. Para nanofios de InN, nos sítios do centro, a energia de formação do CN e CIn é muito próxima, sendo que o CN vai ter distribuição uniforme ao longo do diâmetro, mas na superfície o CIn ser torna mais estável e a estrutura de bandas mostra que esta configuração apresenta níveis doadores rasos. Para impurezas substitucionais de Ge, em nanofios de GaN, observamos que no centro do nanofio, o átomo de Ge tem uma probabilidade maior de ser encontrado no síto do Ga, mas nos sítios da superfície a probabilidade é maior de encontrar no sítio do N, sendo essa a configuração mais estável. Para nanofios de AlN, no centro do nanofio, é possível encontrar o átomo de Ge no sítio do N ou Al, já que a energia de formação é práticamente a mesma. Na superfície a probabilidade maior é de encontrar o átomo de Ge no sítio do N, sendo, também, esta a configuração mais estável. Já para nanofios de InN, o átomo de Ge vai ser encontrado preferencialmente no sítio do In com distribuição uniforme ao longo do diâmetro do nanofio. Analisando a estrutura de bandas do GeIn observamos níveis doadores rasos. Para a impureza substitucional de Si, obtemos que em nanofios de GaN e InN a configuração mais estável, é o Si ser encontrado no sítio do cátion (Ga ou In) nos sítios centrais do nanofio e analizando a estrutura de bandas do SiGa e do SiIn, também observamos níveis doadores rasos. Entratanto, para nanofios de AlN, no centro do nanofio a probabilidade é maior de encontrar o átomo de Si no sítio do Al, mas na superfície a probabilidade é maior de encontrar o átomo de Si no sítio do N, sendo esta a configuração mais estável. Por fim, analisamos a variação do band offset com a variação do diâmetro do nanofios que forma a heteroestrutura. Consideramos heteroestruturas na fase wurtzita e blenda de zinco, pois nos processos de síntese as duas fases são obtidas. Observamos que o resultado é similar para as dias fases e, a medida, que o diâmetro aumenta o valor do band offset também aumenta, tendendo para o valor obtido para o cristal.
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Pemasiri, Karunananda. "Investigation of zincblende, wurtzite, and mixed phase InP nanowires by photocurrent, photoluminescence and time-resolved photoluminescence spectroscopies." University of Cincinnati / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1377873494.
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Kendrick, Chito Edsel. "Revisiting Nitride Semiconductors: Epilayers, p-Type Doping and Nanowires." Thesis, University of Canterbury. Electrical and Computer Engineering, 2008. http://hdl.handle.net/10092/2108.
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This dissertation investigates the growth of high quality GaN and InN thin films by plasma assisted molecular beam epitaxy (PAMBE). It also explores the growth of self-seeded GaN branching nanowires and p-type doping of InN, two topics of particular interest at present.
The growth of high quality III-Nitride semiconductor thin films have been shown to be dependent on the group-III (metal) to nitrogen ratio. A metal-rich growth environment enhances the diffusion of the group-III adatoms through the formation of a group-III adlayer. By using a metal-rich growth environment, determined by growth rate studies using laser reflection interferometry or RHEED analysis of the surface, both GaN and InN films have been grown with a smooth surface morphology. Additionally the smooth surface morphology has beneficial effects on the electrical and optical properties of both materials. However, with the growth using a metal-rich environment, group-III droplets are present on all film surfaces, which can be an issue for device fabrication, as they produce facets in the crystal structure due to enhanced growth rates.
MBE growth of GaN nanowires via the vapour liquid solid (VLS) and vapour solid (VS) growth techniques have so far been based on the N-rich growth regime. However, we have shown that the Ga-rich growth regime can be used to grow self-seeded one dimensional and hierarchical GaN nanowires. 7 µm long hierarchical GaN nanowires with at least three branches were grown and shown to have a high crystalline quality. The suggested growth mechanism is a self-seeding VLS process driven by liquid phase epitaxy at the nanoscale, while the branching growth was nucleated due to the Ga-rich growth regime by excess Ga droplets forming on the trunk during growth. The growth of vertical GaN nanowires has also been achieved using the same self-seeding process and the critical parameter seems to be the Ga to N ratio. Also, the growth rate of the Ga-rich grown GaN nanowires can supersede the growth rates reported from N-rich grown GaN nanowires by at least a factor of two.
The fabrication of vertical and planar GaN nanowire devices has been demonstrated in this study. Two point and three point contacts were fabricated to the branching GaN nanowires in the planar direction with resistive measurements ranging from 200 - 900 kΩ, similar to chemical vapour deposition and MBE grown GaN nanowires. The nonlinear current-voltage characteristics from the three point contacts may lead to unique nano-devices. The planar nanowires have also shown to have potential as UV detectors. Schottky diodes were fabricated on the vertical nanowires, with values for the barrier heights consistent with bulk diodes.
Mg and Zn doping studies of InN were also performed. Both InN:Mg and InN:Zn have strong photoluminescence only at low doping concentrations. However, the InN:Mg films have reduced mobilities with increased Mg content, whereas the mobility determined from the InN:Zn films is independent of Zn. When the InN:Zn film quality was improved by growing under the In-rich growth regime, electrochemical capacitance-voltage results suggest n{type conductivity, and strong photoluminescence was obtained from all of the films with four features seen at 0.719 eV, 0.668 eV, 0.602 eV and 0.547 eV. The features at 0.719 eV and 0.668 eV are possibly due to a near band edge to valence band or shallow acceptor transition, while the 0.547 eV has an activation energy of 60 meV suggesting a deep level acceptor.
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Hoeng, Fanny. "Potential of nanocellulose for conductive ink preparation." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAI078.
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Ce projet vise à développer de nouvelles encres à base de nanofils d’argent et de nanocellulose pour des applications conductrices et transparentes. Les nanocelluloses, nanoparticules issues de la cellulose, sont de deux types : les nanocristaux de cellulose (NCC) et les nanofibrilles de cellulose (NFC) et possèdent des propriétés bien spécifiques. Ce travail a consisté d’une part (i) à utiliser la forme tubulaire et rigide des NCC pour produire des nanotubes d’argents par synthèse chimique, avant leur formulation en encre et d’autre part (ii) à utiliser les propriétés d’enchevêtrement des NFC flexibles pour stabiliser des nanofils d’argent commerciaux, habituellement instables en suspension. Les divers résultats de ce projet ont permis d’aboutir à la formulation brevetée et à la commercialisation d’une encre conductrice à base d’une faible quantité d’argent et de NCC et de deux encres conductrices et transparentes à base de NFC et de nanofils d’argent. Les interactions physico-chimiques et la stabilité colloïdale de ces suspensions hybrides ont été étudiée de manière fondamentale, tout en développant des formulations adaptées à divers procédés d’impression, que ce soit à échelle laboratoire mais aussi industrielleThis project aims at developing new conductive inks based on nanocellulose and silver nanowires for transparent and conductive applications. Nanocellulose are nanoparticles extracted from the cellulose and two kinds currently exist: the cellulose nanocrystals (CNC) and the cellulose nanofibrils (CNF). This project have evaluated on one hand the ability of using tubular rigid CNC as template for producing silver nanorods, prior their formulation into conductive inks. On the other hand, the ability of using flexible and entangled CNF to stabilize commercial silver nanowires, usually unstable in suspension, was investigated. The results of this project lead to the patented formulation and commercialization of one low silver content conductive ink based on silver and CNC and two conductive transparent ink based on CNF and silver nanowires. Physico-chemical interactions and colloidal stability of such hybrid suspension have been scientifically studied meanwhile printing process adapted formulation have been successfully designed and tested at laboratory scale but also industrial scale
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Zhao, Songrui. "Molecular beam epitaxial growth, characterization, and nanophotonic device applications of InN nanowires on Si platform." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=117217.
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Dislocation-free semiconductor nanowires are an extremely promising route towards compound semiconductor integration with silicon technology. However, precise control over nanowire doping, together with the surface charge properties, has remained a near-universal material challenge to date. In this regard, we have investigated the molecular beam epitaxial growth and the correlated surface electrical and optical properties of InN nanowires, a promising candidate for future ultrahigh-speed nanoscale electronic and photonic devices and systems, on Si platform.By dramatically improving the epitaxial growth process, intrinsic InN nanowires are achieved, for the first time, both within the bulk and on the non-polar InN surfaces. The near-surface Femi-level is measured to locate below the CBM, suggesting the absence of surface electron accumulation. Such intrinsic InN nanowires can possess an extremely low free carrier concentration of ~1e13 /cm3, as well as a close-to-theoretically-predicted electron mobility in the range of 8,000 to 12,000 cm2/V·s at room temperature. This result is in direct contrast to the universally observed 2DEG on the InN grown surfaces. Furthermore, the surface charge properties of InN nanowires, including the formation of 2DEG and the optical emission characteristics can be precisely tuned, for the first time, through the controlled n-type doping.More importantly, p-type doping into InN nanowires is also realized, for the first time. The presence of Mg-acceptors is clearly demonstrated by the PL spectra. Furthermore, p-type surface is observed from the XPS experiments, indicating the presence of free holes. Additionally, p-type conduction is directly measured by single nanowire field effect transistors.In the end of this thesis, InN nanowire p-i-n photodiodes are fabricated, with a light response up to the telecommunication wavelength range at low temperatures. This thesis work provides a vivid example, and paves the way for the rational “materials by design” development of silicon integrated InN-based device technology in the nanoscale.Les nanofils semi-conducteurs sans dislocations sont une voie très prometteuse vers l'intégration des semi-conducteurs composés avec la technologie silicium. Cependant, un contrôle précis de dopage des nanofils, ainsi que les propriétés de charge de surface, reste un défi universel à ce jour. À cet égard, nous avons étudié la croissance épitaxiale par faisceau moléculaire et les propriétés de surface corrélés électriques et optiques des nanofils de InN sur du substrat de silicium, qui ont émergé comme candidat prometteur pour l'avenir des dispositifs électroniques et photoniques à très haute vitesse et à échelle nanométriques.Pour la première fois, en améliorant le processus de croissance épitaxiale, InN intrinsèque est atteint, à la fois dans le volume et sur les surfaces non polaires de InN. Le niveau de Fermi à la surface est mesuré et localisée sous le CBM, ce qui suggère l'absence d'accumulation d'électrons en surface. Ces nanofils InN intrinsèques possédent une concentration de porteurs libres très faible ~1e13 /cm3, ainsi que d'une mobilité proche de le théoriquement prédite d'électrons entre 8000 à 12000 cm2/V·s à température ambiante. Ce résultat est en contraste direct avec les 2DEG observés sur les surfaces d'InN. En outre, les propriétés de charge de surface de nanofils InN, y compris la formation de 2DEG et les caractéristiques d'émission optiques, peut être réglé avec précision, pour la première fois, par l'intermédiaire du contrôle d'incorporation de dopants de type n.Plus important encore, dopage de type p dans les nanofils InN est également réalisé pour la première fois. La présence de niveaux d'énergie Mg-accepteur est démontrée par les spectres de PL. Dans ces nanofils dopés de Mg, il n'y a pas d'accumulation d'électrons de surface et le niveau de Fermi dans le volume est proche de la VBM, ce qui indique un matériau de type p.En fin, la jonction p-i-n basé sur des nanofils InN photodétecteurs qui peut être utilisé en mode photovoltaïque est démontrée, avec une réponse à la lumière jusqu'à la longueur d'onde des télécommunications à de basses températures. Ce travail de thèse fournit un exemple frappant, ainsi que prépare le terrain pour le développement "matériaux par conception" de la technologie des dispositifs en silicium intégrée à base InN à l'échelle nanométrique.
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Domènech, i. Amador Núria. "Phonons in III-nitride thinfilms, bulk and nanowires: a closer look into InN vibrational properties." Doctoral thesis, Universitat de Barcelona, 2015. http://hdl.handle.net/10803/348867.
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This thesis is devoted to the study of the interactions of phonons in indium nitride (InN) and materials of the (In,Ga)N system with wurtzite structure. For this purpose, we present Raman spectroscopy on nanowires (NWs), thin films and bulk samples, in order to adress phonon interactions in these materials. We also present Brillouin spectrsocopy measurements of InN thin films, from which a reliable set of elastic constants is proposed.
We have studied the phonon anharmonic interactions and phonon decay channels of InN, both in thin films and NWs. The temperature dependence of Raman peak width of all the phonon modes has been studied using a model that considers the contribution of three- and four-phonon processes, taking into account the phonon density of states obtained by ab-initio calculations.
In InN thin films, we find that the E2h phonon mode mainly decays through 4-phonon processes, whereas the extremely narrow E2l mode can decay only through up-conversion processes. The LO and the TO modes are found to decay through 3-phonon and 4-phonon interactions. In InN NWs we found the same phonon decay channels but phonon linewidths are significantly reduced, indicating a higher crystalline quality. The lifetimes of the phonon modes are derived from the measured phonon linewidths. The long-lived E2l phonon exhibits the largest lifetime, which is mainly limited by impurity scattering. We also study the anharmonic decay of high-frequency LVMs H complexes in Mg-doped InN, which can be explained by considering dephasing due to quasi-elastic acoustic phonon scattering.
We have discussed the relevant electronic resonances that affect Raman scattering in the (In,Ga)N system. We show that the optical excitation of the longitudinal optical modes in InN occurs via the Martin's double resonance both in InN layers and nanostructures, even though the defect density of the latter is significantly lower. By performing wavelength-dependent measurements on InN thin films and NWs, the A1(LO) and the E1(LO) wave-vector dispersion close to zone-center have been obtained. We have also studied the impurity-mediated cascade mechanism of multiphonons in InGaN layers. To ascertain the role of the impurities we have studied as-grown samples in comparison with He+-implanted InGaN layers. UV Raman-scattering measurements allow us to measure up to fifth order multiphonon scattering due to cascade mechanism. Relative multiphonon intensities depend on the indium concentration and implantation dose.
Finally, we have studied the LO-Phonon-Plasmon Coupled Modes (LOPCMs) in InN and GaN using the Lindhard-Mermin model. We have determined the electron density in undoped, Si-doped and Mg-doped NWs. We have also studied a bulk, ammonothermally-grown Si-doped GaN sample. No evidence of LOPCMs was detected in the Ga-polar face, probably due to the higher defect density existing in this sample sector. We have detected both branches of the LOPCMs in the N-polar face, and we have made a study of the distribution of the free charge density by means of confocal micro-Raman measurements.Aquesta tesi està dedicada a l’estudi de les interaccions dels fonons en nitrur d'indi (InN) i en semiconductors del sistema (In.Ga)N amb estructura wurtzita. Amb aquest objectiu es presenten estudis d'espectroscòpia Raman en capes primes, nanofils (NWs), i mostres bulk, que han permès abordar de manera global les interaccions dels fonons en aquests materials. Hem estudiat les interaccions anharmòniques i els canals de decaïment dels fonons de InN, tant en capes primes com en NWs. La dependència de l’amplada del pic Raman amb la temperatura de tots els modes fonònics s’ha estudiat utilitzant un model anharmònic que considera la contribució dels processos de tres i quatre fonons, i tenint en compte la densitat d'estats de fonons obtinguda mitjançant càlculs ab-initio. L'anàlisi dels temps de vida fonònics i de la dependència amb temperatura de les freqüències permet afirmar que els NWs tenen una estructura més relaxada que les capes primes. També hem estudiat el decaïment anharmònic de modes locals de vibració corresponents a complexos d'H en InN fortament dopat amb Mg. Hem estudiat les ressonàncies en el sistema (In,Ga)N i la influència de la densitat d’impureses en l’eficiència dels mecanismes ressonants. Hem demostrat que la dispersió Raman de modes òptics longitudinals en el InN es produeix a través de la doble ressonància del Martin tant en capes primer com en nanoestructures, tot i que la densitat de defectes d'aquestes últimes és significativament menor. Hem estudiat també el mecanisme de cascada mediat per impureses, a través del qual es produeix la dispersió de multifonons, en capes primes de InGaN amb diferent composició i diferent grau d’implantació d'ions d'He, i hem comprovat que les intensitats relatives dels multifonons depenen de la concentració d’indi i de la dosi de la implantació. Finalment, hem estudiat l’acoblament de fonons polars amb els plasmons mitjançant el model dielèctric de Lindhard-Mermin, amb la finalitat d’investigar la densitat d’electrons lliures utilitzant espectroscòpia Raman. Hem determinat la concentració d'electrons en NWs de InN sense dopar, dopats amb Si i dopats amb Mg. També hem fet un estudi de la distribució de la densitat de càrrega en una mostra de GaN ammonotermal mitjançant mesures de micro-Raman confocal.
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Nieto, González Luis. "Origem e estabilidade de nanoestruturas de InAs sobre ligas de InP e InGaAs." [s.n.], 2007. http://repositorio.unicamp.br/jspui/handle/REPOSIP/278482.
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Orientador: Mônica Alonso CottaTese (doutorado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin
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Resumo: Neste trabalho estudamos os mecanismos de crescimento durante a epitaxia por feixe químico de nanoestruturas III-V baseadas no sistema InAs/InP. Particularmente, foram estudados nanofios e ilhas de InAs sobre uma camada buffer InP(001) e nanofios de InAs sobre uma matriz de InGaAs/InP (com mesmo parâmetro de rede). Apresentaremos, nesta tese, as diferenças e similaridades destes sistemas quanto a condições de crescimento, distribuição de tamanho, forma e os efeitos de volume da camada de InGaAs sobre as nanoestruturas de InAs quando comparadas ao sistema InAs/InP. Nossa escolha do InGaAs/InP como camada buffer para a nucleação dos fios de InAs, foi feita porque facilitaria a utilização deste sistema em diversas aplicações, proporcionando maior flexibilidade no desenho dos dispositivos. Por outro lado, este material abre a possibilidade de controlar as características das nanoestruturas através das propriedades de bulk e superficiais da liga ternária InGaAs. Além disso, ligas ternárias podem exibir efeitos de volume que afetam suas propriedades superficiais. Estes fenômenos podem afetar a nucleação dos fios quânticos e por isso foram objeto de nosso estudo. Para isso utilizamos e correlacionamos medidas in situ de difração de elétrons de alta energia (RHEED), microscopia de força atômica (AFM) e eletrônica de transmissão (TEM), com os resultados obtidos por difração de raios X com incidência rasante (GIXD). Verificamos, deste modo, tanto a influência das condições de crescimento, como o comportamento da relaxação da energia elástica nas nanoestruturas. Com todos estes resultados mostramos como acontece a evolução da deformação nos nanofios e pontos quânticos de InAs/InP e como acontecem as transições de forma entre estes dois tipos de nanoestruturas, em função das condições de crescimento e tipo de superfície do substrato utilizado. Mostramos, também que a introdução de um composto ternário (InGaAs) entre o InAs e o InP não afeta significativamente a forma e tamanho das nanoestruturas quando comparadas ao caso InAs/InP. Em particular, a interdifusão gerada por variações locais da composição na camada buffer em nanofios de InAs pode ser minimizada através de mudanças nas condições de crescimento do InGaAs
Abstract: In this work we study the growth mechanisms of III-V nanostructures by chemical beam epitaxy (CBE) based on the InAs/InP materials system. Particularly, nanowires and nanodots of InAs on InP (001) and InAs nanowires on InGaAs/InP (lattice matched) buffer layers were studied. The differences and similarities of these systems are presented in this text, as a function of growth conditions, size distribution, as well as the bulk effects of the InGaAs layer on InAs nanostructures when compared to the InAs/InP system. Our choice of InGaAs/InP buffer layer for InAs nanowire nucleation was due to the possible use of this system in many applications, providing greater flexibility in device design. Furthermore, this material opens up the possibility of controlling nanostructures characteristics through bulk and surface properties of the InGaAs ternary alloy. In other hand, ternary alloys may present volume effects that affect their surface properties. These phenomena can affect quantum wires nucleation and thus became one of the subjects of our study. With these goals in mind, we have correlated in situ high-energy electrons diffraction (RHEED) measurements, atomic force microscopy (AFM) and transmission electron microscopy (TEM) images with the results obtained by grazing incidence X-ray diffraction (GIXD). We report here the influence of the growth conditions on nanostructure shape as well as the behavior of elastic energy relaxation within the nanostructures. Our results show how the evolution of deformation within InAs/InP nanowires and quantum dots occur and how the shape transition between these two types of nanostructures depend on the growth conditions and the substrate surface type used. We also show that the introduction of a ternary compound (InGaAs) between InAs and InP does not significantly affect the shape and size of nanostructures as compared to the InAs / InP case. In particular, the interdifusion generated in InAs nanowires by local variations in the buffer layer composition can be minimized through changes in InGaAs growth conditions
Doutorado
Estrutura de Líquidos e Sólidos; Cristalografia
Doutor em Ciências
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Ainsworth, Catherine. "Structure-property relationships in conductive nanowire networks." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/structureproperty-relationships-in-conductive-nanowire-networks(0a8901bc-54be-4882-b49d-3e5515fac0df).html.
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This thesis studies networks of silver nanowires as a transparent conducting electrode material and presents an investigation into the relationship between electrical and optical properties in the networks. The work focusses on two main aspects: the production of networks via different deposition methods; and the development of a predictive model based on theory that relates the sheet resistance to the optical transmittance. The deposition methods of drop-casting, bar-coating and spray-coating are used to create networks and the randomness of these networks is compared using image analysis in ImageJ, a public domain image processing program, and Wolfram Mathematica, a computer algebra program. It is determined that spray-coating results in the most random networks, therefore all subsequent experiments are carried out using this as the deposition method. Annealing condition tests are carried out on the nanowire networks to determine the optimal annealing conditions required to burn off poly(vinyl pyrrolidone) (PVP) remaining from the nanowire synthesis process and sinter the nanowire junctions to improve network conductivity. The sheet resistances and optical transmittances of the networks are measured and compared to networks created by other research groups. It is found that the networks created in this study exhibited similar optical and electrical properties to those in the literature, obtaining Rs = 100 Ω/sq for T = 81%.The developed model is based on theory and relates the sheet resistance to the optical transmittance using only the length and width of the nanowires used in the network and the mean network coverage as variables. The model can be used to predict the properties of a network if these factors are known. The model is compared with experimental data both from this study and from the literature, along with simulated data from the literature that was obtained by Monte Carlo methods. It is shown that there is an excellent fit between the model and all data that it is compared with. It is demonstrated that < 1% of the network coverage is greater than 2 for typical nanowire networks, proving that the networks are two-dimensional and therefore do not require a bulk regime to describe the relationship, as has been suggested in prior work.
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Schneider, Ina Alexandra [Verfasser], and Christoph [Akademischer Betreuer] Strunk. "Superconductor-Insulator Transition and Charge-Phase Duality in TiN Nanowires / Ina Alexandra Schneider ; Betreuer: Christoph Strunk." Regensburg : Universitätsbibliothek Regensburg, 2018. http://d-nb.info/1149920327/34.
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Schneider, Ina Alexandra Verfasser], and Christoph [Akademischer Betreuer] [Strunk. "Superconductor-Insulator Transition and Charge-Phase Duality in TiN Nanowires / Ina Alexandra Schneider ; Betreuer: Christoph Strunk." Regensburg : Universitätsbibliothek Regensburg, 2018. http://nbn-resolving.de/urn:nbn:de:bvb:355-epub-356917.
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Hadj, Alouane Mohamed Helmi. "Vers des émetteurs de lumière de longueurs d’ondes contrôlées à base de nanostructures InAs/InP." Thesis, Lyon, INSA, 2013. http://www.theses.fr/2013ISAL0045/document.
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La complexité des systèmes de télécommunications par fibre optique évolue rapidement de façon à offrir plus de bande passante. Comme ce fut le cas pour l’industrie de la microélectronique, l’intégration de composants photoniques avancés est requise pour la production de composants de haute qualité aux fonctions multiples. C’est dans ce contexte, que s’inscrit ce travail qui consiste à contrôler la longueur d’onde d’émission des nanostructures InAs fabriquées dans deux types matrice InP. En effet, le premier volet de ce travail consiste à étudier les îlots quantiques InAs dans une matrice d’InP massif et sera dédié principalement à l’investigation de l’impact de l’interdiffusion sélective sur les propriétés optiques de bâtonnets quantiques (BaQs) élaborées par l’épitaxie par jets moléculaires (EJM). Un prototype d’une source modulable en longueur a été achevé à base de ces hétérostructures. Un modèles théorique qui traite de l’activation et du transfert thermique des porteurs à travers les BaQs de différentes tailles, créés par l’implantation ionique contrôlée a été développé. Les acquits obtenues dans le premier thème nous ont permis d’aborder une deuxième thématique très concurrentielle liée à l’étude des structures à Nanofils (NFs) InP et des hétérostructures à nanofils InAs/InP allant des structures 1D cœur/coquilles aux structures contenant une BQ InAs par nanofil InP par EJM en mode VLS (Vapeur-Liquide-Solide) sur substrat silicium. Nous avons révélé par différentes techniques spectroscopiques (PL, excitation de PL, microPL, PLRT) des propriétés optiques très spécifiques et particulièrement intéressantes : fort rapport surface/volume impactant sur les durées de vie des porteurs photocrés, présence de différentes phases cristallines (Wurtzite et Zinc-blende) au sein d’un même nanofil en fonction des conditions de croissance. Nous avons pu réaliser des couches actives des émetteurs à base de NFs dans lesquels nous avons privilégié la formation de segments d’InAs assimilables à des boîtes quantiques avec une forte localisation spatiale des porteurs et un très fort maintient de la luminescence en fonction de la température. Les mesures de PL montrent que les segments d’InAs émettent dans la gamme 1.3-1.55 µm ce qui montre le potentiel d’applications de ce type de nanofils dans une technologie des télécommunications par fibres optiquesLa complexité des systèmes de télécommunications par fibre optique évolue rapidement de façon à offrir plus de bande passante. Comme ce fut le cas pour l’industrie de la microélectronique, l’intégration de composants photoniques avancés est requise pour la production de composants de haute qualité aux fonctions multiples. C’est dans ce contexte, que s’inscrit ce travail qui consiste à contrôler la longueur d’onde d’émission des nanostructures InAs fabriquées dans deux types matrice InP. En effet, le premier volet de ce travail consiste à étudier les îlots quantiques InAs dans une matrice d’InP massif et sera dédié principalement à l’investigation de l’impact de l’interdiffusion sélective sur les propriétés optiques de bâtonnets quantiques (BaQs) élaborées par l’épitaxie par jets moléculaires (EJM). Un prototype d’une source modulable en longueur a été achevé à base de ces hétérostructures. Un modèles théorique qui traite de l’activation et du transfert thermique des porteurs à travers les BaQs de différentes tailles, créés par l’implantation ionique contrôlée a été développé. Les acquits obtenues dans le premier thème nous ont permis d’aborder une deuxième thématique très concurrentielle liée à l’étude des structures à Nanofils (NFs) InP et des hétérostructures à nanofils InAs/InP allant des structures 1D cœur/coquilles aux structures contenant une BQ InAs par nanofil InP par EJM en mode VLS (Vapeur-Liquide-Solide) sur substrat silicium. Nous avons révélé par différentes techniques spectroscopiques (PL, excitation de PL, microPL, PLRT) des propriétés optiques très spécifiques et particulièrement intéressantes : fort rapport surface/volume impactant sur les durées de vie des porteurs photocrés, présence de différentes phases cristallines (Wurtzite et Zinc-blende) au sein d’un même nanofil en fonction des conditions de croissance. Nous avons pu réaliser des couches actives des émetteurs à base de NFs dans lesquels nous avons privilégié la formation de segments d’InAs assimilables à des boîtes quantiques avec une forte localisation spatiale des porteurs et un très fort maintient de la luminescence en fonction de la température. Les mesures de PL montrent que les segments d’InAs émettent dans la gamme 1.3-1.55 µm ce qui montre le potentiel d’applications de ce type de nanofils dans une technologie des télécommunications par fibres optiques
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Yang, Kai. "Fabrication and characterization of silicon nanowires for devices applications compatible with low temperature (≤300 ˚C) flexible substrates." Thesis, Rennes 1, 2019. http://www.theses.fr/2019REN1S123.
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La fabrication et la caractérisation de nanofils de silicium à basse température (≤300 °C) a été menée suivant deux approches: par la méthode des espaceurs et par la méthode de croissance Solide Liquide Solide (SLS). La synthèse des nanofils de silicium a été étudiée à l'aide de deux technologies de dépôts: le dépôt CVD assisté par plasma (PECVD) et le dépôt à couplage inductif (ICP CVD). Les études ont démontré la faisabilité des nanofils de silicium par le procédé ICP-CVD. De plus, les propriétés d'isolation électrique des couches de SiO2 et la fabrication de transistors à effet de champ à couche mince ont été démontrées à l'aide de la technologie de dépôt plasma ICP. Par ailleurs, des nanofils de silicium ont été synthétisés par le procédé SLS à 250 ° C utilisant l'indium comme catalyseur. La croissance 3D de ces nanofils à partir de substrats de silicium (film mince de silicium monocristallin ou amorphe) a été démontrée. Les nanofils sont obtenus sous plasma d'hydrogène. Des études ont été menées en fonction de l'épaisseur de l'indium déposé, de la durée et de la température du plasma d'hydrogène. Les résultats originaux obtenus permettent d'envisager la possibilité de fabriquer des dispositifs électroniques à base de ces nanofils de silicium sur des substrats flexibles basse températureThe fabrication and characterization of silicon nanowires (SiNWs) at low temperature (≤300° C) has been focused for two mainstream approaches: spacer method and Solid Liquid Solid method. The feasibility of such silicon nanowires has been explored using two deposition technologies: conventional plasma enhanced deposition (PECVD) and inductively coupled plasma deposition (ICP CVD). The studies demonstrated the feasibility of silicon nanowires using the ICP CVD process. In addition, the electrical insulation properties of SiO2 layers and the fabrication of thin-film field effect transistors were demonstrated using ICP plasma deposition technology. Furthermore, indium catalyzed SLS SiNWs were fabricated for the first time at 250 °C. Synthesis of 3D SiNWs by SLS process from silicon substrates (monocrystalline or amorphous silicon thin film) has been demonstrated. The growth of nanowires is obtained under hydrogen plasma. Studies were conducted based on the thickness of indium deposited, duration and temperature of the hydrogen plasma. All these results were concluded originally and they enable the possibility of fabrication of SiNWs based electronic devices onto low temperature flexible substrates
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Zeghouane, Mohammed. "Contrôle de l'homogénéité et de la composition en indium dans les nanofils InGaN synthétisés par HVPE." Thesis, Université Clermont Auvergne (2017-2020), 2019. http://www.theses.fr/2019CLFAC031/document.
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Ce mémoire traite de l’étude de la croissance de nanofils (In,Ga)N par épitaxie en phase vapeur par la méthode aux hydrures (HVPE). L’objectif est de contrôler l’homogénéité, la composition et les dimensions des fils. La première partie de ce travail est consacrée à l’étude de la croissance auto-organisée de nanofils InGaN par HVPE. Les résultats montrent qu’il est possible de maitriser la composition des fils en indium, de 7 % à 90 %, en ajustant la composition de la phase vapeur. Des caractérisations structurales confirment une très bonne qualité cristalline des nanofils InGaN obtenus ainsi qu’une parfaite homogénéité sur leurs longueurs. Ce travail expérimental a été couplé à un travail de modélisation théorique basée sur des calculs thermodynamiques. Un deuxième travail portant sur l’étude de l’épitaxie sélective de réseaux de fils (In,Ga)N sur des templates GaN/c-Al2O3, masqués par un diélectrique, est réalisée. La croissance, parfaitement sélective et reproductible, de nano- et microrods d’InN de très bonne qualité cristalline est démontrée pour la première fois par HVPE. Une étude systématique sur l’influence des paramètres de croissance a permis de déterminer la hiérarchie des vitesses de croissance des différentes facettes des rods et d’identifier les phénomènes physiques mis en jeu. Un modèle de croissance basé sur les énergies de surface et d’interface est proposé afin d’expliquer la présence d’un creux dans les rods d’InN. Des études en photoluminescence sur des ensembles de nanorods d’InN ont mis en évidence un fort dopage de type n et indiquent également la présence d’une surface d’accumulation des porteurs de charge sur les parois des rods. Enfin, l’étude de la faisabilité de la croissance sélective d’InGaN par HVPE est initiéeThis thesis focuses on a comprehensive study of (In, Ga)N nanowires grown by hydride vapor phase epitaxy (HVPE), combining the growth technology, complementary chemical and structural analyses and theoretical modeling. The first part of this work is devoted to the study of the self-induced growth of InGaN nanowires by HVPE. The end result shows that growth of vertically aligned InGaN nanowires with a high crystalline quality can be synthesized by this cost-effective technique. The indium content can be varied from 7 % to 90 % with a high degree of homogeneity along the nanowire length with a good crystal quality. This is achieved by understanding the kinetics of interconnected chemical reactions in the vapor phase, and coupling them with the kinetically controlled composition of solid nanowires. The second focus section of this work looks at the selective area growth of (In, Ga)N nanorods. Well-ordered and vertically aligned InN nano and microrods with high aspect ratio and high crystalline quality are synthetized by HVPE using the SAG approach. The growth occurs through the apertures of a SiNx masked Ga-polar GaN/c-Al2O3 template for adjusted growth temperature and V/III ratio. A systematic study of the evolution of InN nanorods shape under various growth conditions: growth temperature, growth time and the input NH3 partial pressure, is investigated. A growth model based on surface and interface energies is proposed to explain the presence of a void in these InN nanorods. Photoluminescence measurements on InN nanorods reveal strong n-type doping and indicate the presence of a carrier accumulation on the nanorods surfaces. Finally, the selective growth feasibility of InGaN nanorods by HVPE is initiated
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Alzahrani, Hanan Yahya S. "Non linear piezoelectricity in wurtzite semiconductor core-shell nanowires : an atomistic modelling approach." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/non-linear-piezoelectricity-in-wurtzite-semiconductor-coreshell-nanowires-an-atomistic-modelling-approach(b4be879a-b85f-4e58-81d7-79f304baa23d).html.
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Piezotronics is a new field, as first explored by Professor Zhong Lin Wang (Georgia Institute of Technology, Atlanta, USA), which describes the exploitation of the piezoelectric polarization and internal electric field inside semiconductor nanostructures by applying strain, to develop electronic devices with new functionality. Such concepts find applications in both III-V and II-VI semiconductor compounds, in optics, optoelectronics, catalysis, and piezoelectricity, sensors, piezoelectric transducers, transparent conductor and nanogenerators. In this work I explore the strain dependence of the piezoelectric effect in wurtzite ZnO crystals. The Linear and quadratic piezoelectric coefficients of III-V (GaP, InP, GaAs and InAs) wurtzite semiconductors are also calculated using ab-initio density functional theory. The polarization in terms of the internal anion–cation displacement, the ionic and dipole charges is written and the ab initio Density Functional Theory is used to evaluate the dependence of all quantities on the strain tensor. The piezoelectric effect of III–V semiconductors are nonlinear in the strain tensor. The quadratic piezoelectric coefficients and a revised value of the spontaneous polarization are reported. Furthermore, the ZnO nanowires is found to be non-linear piezoelectric effect and leads to predictions in some cases opposite to those obtained using the widely used linear model. The predicted magnitude of such coefficients are much larger than previously reported and of the same order of magnitude as those of III-N semiconductors. We also model the bending distortion created on a III-V wurtzite nanowire by an atomic force microscope tip induced deflection to calculate the piezoelectric properties of both homogenous and core shell structures. A number of combinations of III-V materials for the core and the shell of the nanowires, are shown a favour much increased voltage generation. The largest core voltages in core/shell combinations of InAs/GaP, InP/GaP, GaP/ InAs and GaP/InP are observed which can be theoretically 3 orders of magnitude larger than the typical values of ±3V in homogenous nanowires. Also considering properties such as bandgap discontinuity and mobility, III-V wurtzite core shell nanowires are candidates for high performance components in piezotronics and nanogeneration.
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Hummelgård, Magnus. "In-situ TEM Probing of Nanomaterials." Doctoral thesis, Mittuniversitetet, Institutionen för naturvetenskap, teknik och matematik, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-8998.
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Nanomaterials because of their small size, may have special properties unlikely to be seen in ordinary types of materials. Nanomaterials like nanotubes,nanowires and nanoparticles are best studied at the nanoscale, vital but also problematic. In this thesis we use a transmission electron microscope (TEM)combined with a scanning tunneling microscope probe. This system allows TEM images to be captured and recorded into a movie together with recordedelectrical data for real time analysis. Using this method we found that the electrical conductivity of molybdenumbased nanowires Mo6S3I6 can be improved by current induced transformation. This might be a general method of improving nanowires which is of high valueif the wires are to be used in electrical circuits or field emission devices. The bending modulus for these nanowires were also determined, by an electromechanical resonance method, to 4.9 GPa. The sintering phase of silver nanoparticles, used in electrical conductive ink for printing electrical circuits, were studied by the in-situ TEM probing method. We observed that percolation path ways are formed and that the dispersive agent of the particles can be pyrolysed into a net of carbon with characteristics similar to graphite. We also developed a method for decorating nanowires and nanotubes with gold nanoparticles. Nanowire particle composites are often used in assembling more complex devices (electronic circuits) or for linking to organic molecules (biosensor applications) and existing particle decoration methods are either difficult or with low yield. By in situ TEM probing we found that carbon nanocages can be grown onto these gold nanoparticles. The size of the gold nanoparticles is controllable an thus the size of the nanocages. These nanocages may be used in medicine- or hydrogen storage-applications.Nanomaterial har givits stort intresse under det senaste årtiondet, detta på grund av deras unika egenskaper som gör att de i många hänseenden överträffar traditionella material. Egenskaperna beror till största del på storlek och därför är det nödvändigt att studera dessa material på nanonivå, något som är problematiskt. För sådana studier krävs ett instrument med tillräckligt hög upplösning på nanonivå samt ett system med en prob som möjligör selektion och karakterisering utav individuella byggstenar. I denna avhandling används ett transmissionselektronmikroskop (TEM) tillsammans med ett sveptunnelmikroskop (STM) där det senare används som prob. Systemet medger studier på nanonivå och karakterisering av enskilda byggstenar under realtids avbildning (in situ). Metoden medger en bättre överblick och hanterbarhet vid nanomanipulering än vad till exempel atomkraftmikroskopi medger. Piezodrivna probar kan även användas i svepelektronmikroskop men dessa medger inte samma upplösning som transmissionselektronmikroskopet. Nanotrådar av Mo6S3I6 är ett alternativt material till kolnanorör och överträffar dessa i form av löslighet i båda organiska såväl som polära lösningsmedel. De är enkla att syntetisera men deras elektriska konduktivitet är låg. Mo6S3I6 nanotrådar studerades med in situ TEM probing. Vi fann att genom att driva en tillräckligt hög elektrisk ström genom nanotråden så resulterade detta i en omvandling till en solid metallisk molybden nanotråd med en konduktivitet nära värdet för bulkmaterialet. Resultat är intressant då nanotrådar kan användas i t.ex. fältemission, men resultatet visar också på att det kan vara en generell metod för att förbättra nanotrådar överlag. På dessa nanotrådar har även en elektromekanisk resonans studie utförts där böjmodulen för materialet bestämdes till 4.9 GPa. Med in situ-TEM-probing metoden har även silvernanobläck studerats under en sintringsprocess. Studien visade att vid sintringen så bildas perkulativa vägar genom bläckets silvernanopartiklar samt att vid hög sinteringstemperatur förkolnades det lösningsmedel som silvernanopartiklarna är lösta i. Förkolningen av lösningsmedlet resulterade i ett kolnät med liknande egenskaper som för grafit. Förståelse utav sinteringsprocessen är nödvändig eftersom vid tryckning av elektriskt ledande banor på papper används sintring för att höja ledningsförmågan. Genom att växa nanopartiklar på nanotrådar förändras deras egenskaper och tillämpningar. Existerande metoder är endera komplicerade eller ger dåligt ut- byte. Ett enkelt recept för att växa guldnanopartiklar på kolnanorör och Mo6S3I6 nanotrådar har därför tagits fram. Dessa kolnanorör och nanotrådar har sedan studerats med in-situ-TEM-probing metoden som visade att utanpå dessa guldnanopartiklar kan burar av kol skapas. Eftersom partiklarnas storlek kan kontrolleras kan även kolnanoburarnas storlek kontrolleras. Burarna har användningsområden t.ex. inom medicin och vid lagring av vätgas.
The thesis covers six scientific papers
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Hung, Tsu-Chang, and 洪子昌. "Enhanced Photoresponse and Gas Sensing of InP Nanowire Device." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/77654712064868087216.
Full textAbstract:
碩士國立交通大學
電子物理系所
98
The dimension of electronic devices are reduced further and further from micrometer to nanometer scale and the electrical contact area is squeezed in size by 2-3 orders of magnitude. As a consequence, the contact resistance of nanoscale devices could be hundred or thousand times larger than that of conventional devices and dominant to the total resistance of devices. Indium phosphide (InP) nanowires were synthesized by using a self-seeded, solution-liquid-solid growth method and were stored in a toluene solvent. InP nanowires are ~ 20 nm in diameter and 2-5 μm in length. By using a standard electron-beam lithography technique, two-probe InP nanodevices were fabricated. In order to improve the electrical contact and to diminish the total resistance, all of InP nanowire devices were annealed at 400 °C in a high vacuum for 1 min before measurements of current-voltage curves. The room-temperature resistance of these devices varied considerably although the InP nanowires were picked up from the same source and the dimensions of the nanowires and devices were kept the same. It was conjectured that the difference of room-temperature resistance comes from the contribution of contact resistance. According to the temperature behaviors, the nanowire devices can be categorized into nanowire- and contact-dominated ones. The temperature dependent resistance follow the thermally activated and variable range hopping transport at high and low temperatures, respectively. Moreover, as for high room-temperature resistance devices, the temperature range of resistance following the thermally activated transport shrinks, implying that the contact is deteriorated and dominant to the total resistance. On the other hand, both nanowire- and contact-dominated devices were exposed to light and oxygen gas to see any different responses. Surprisingly, in comparison with the nanowire-dominated devices, the contact-dominated devices always exhibit a much higher ratio of resistance changes in response to either light or oxygen gas exposures.
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Chang, Chia-Hung, and 張家弘. "The optoelectronic characteristics on the InP nanowire field-effect transistors." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/85364552939487000047.
Full textAbstract:
碩士國立交通大學
電子物理系所
97
Indium phosphide (InP) nanowires with an average diameter of 20 nm were grown for the fabrication of two-probe devices by using the standard electron-beam lithography technique. Current-voltage (I-V) behaviors of the nanowire devices were measured at temperatures from 300℃ down to 120℃. The resistance of the nanowire devices increases with decreasing temperatures, implying the semiconducting behavior in the nanowires. The electron transport as well as the temperature dependent resistance R(T) was calculated. We found that, for the devices having low room-temperature resistance, the R(T) agrees well with the thermal activated transport theory. The low resistance devices might give the intrinsic electrical poperties of the InP nanowires. On the other hand, the high resistance devices could be used to study the electrical properties from the nanocontact. Additionally, the back gate technique was adopted to check the field-effect properties. Electrical characterization on the InP nanowire field-effect transistors indicates that the InP nanowires are natively n-type semiconductors. Moreover, the optoelectronic properties of the two-probe nanowire devices were explored under the exposure of the green light laser (532 nm). We found that the photocurrent, in comparison with the dark current, enhances with a ratio up to 100% for the contact dominated devices while the excited photocurrent is still smaller than that in the nanowire dominated devices.
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Tsang-Ho-Yang and 楊倉和. "Molecule-Sensitized Photoconductivity in Single InN Nanowires." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/7frq8v.
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碩士國立臺北科技大學
機電整合研究所
96
In this study, the electronic transport and photoconductivity of single indium nitride (InN) nanowires have been investigated. The monocrystalline InN nanowires have been successfully synthesized by metalorganic chemical vapor deposition (MOCVD). Single InN nanowire devices with focused-ion-beam-deposited (FIB) Pt contacts have been fabricated for the dark- and photo- conductivities studies. Temperature-dependent resistivity measurement shows the weak semiconducting rather than metallic behavior of the as-grown InN nanowires. Under the 808 nm excitation, the single InN nanowires reveal a long lifetime mechanism of carrier. It is found that both the dark- and photo- currents are enhanced in vacuum compared to that in air. This result indicated that physisorbed oxygen molecules could create charge surface state as electron trap on this nitride nanowire.
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Lin, You-Deng, and 林酉燈. "Microwave-induced DC current in an InN nanowire device in magnetic fields." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/88710581854224081206.
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碩士國立中興大學
物理學系所
98
We report on the microwave-induced current in an InN nanowire (NW) device in magnetic fields (B) at 1.4 K. The InN NW has a diameter of about 200nm, and Pt electrodes defined by focus ion beam (FIB). At frequencies ranging from few hundred MHz to 24 GHz, we observed a significant microwave-induced DC current through the device. This current also exhibits an oscillatory behavior in B with a period of about 1 T. The oscillating part has an anti-symmetry dependence with respect to the reversal of B, indicating that it is related to a process with broken time-reversal symmetry. We also examined the power dependence of the current signal and found that the induced current is proportional to the microwave power, following the theoretical prediction for a mesoscopic diffusive-transport junction.
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Huang, Ko-Chih, and 黃格致. "Fabrication and characterization of GaN nanowires, In2O3 nanostructures and InN material." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/67935358179904193821.
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Nai-JenKu and 古乃任. "Obliquely Aligned InN Nanowire Array Grown by Molecular Beam Epitaxy for Nanopiezotronics and Nanogenerators." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/51020706193930354100.
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博士國立成功大學
材料科學及工程學系碩博士班
101
This dissertation proposes an obliquely aligned InN nanowire (NW) array to maximize NW deformation in nanopiezotronics and nanogenerators. The proposed nanogenerator consists of obliquely aligned InN NWs that are deposited by glancing angle deposition with molecular beam epitaxy. This configuration maximizes the bending deformation produced by a normal force, which is limited by the empty space between adjacent NWs and the mechanical strength of the NWs. Thus, this configuration enhances the piezopotential and output power. In the first part of the dissertation, the luminescence of InN NWs is demonstrated to be surface-dependent by precisely controlling the different facets exposed at the surface of an obliquely aligned NW array, as carrier recombination interacts with different material surfaces. In addition to the bulk near-band-edge emission at approximately 0.7 eV from the inner core region, two more peaks with even stronger luminescence intensity appear at 0.86 and 0.91 eV, ascribed to the top-flat c- and the semipolar r-planes, respectively. This surface dependence luminescence phenomenon allows for the development of novel optoelectronic devices. The surface-dependent piezotronic current-voltage (I-V) characteristics of the InN NW array with exposed c- and r-planes were studied by conductive atomic force microscopy. The effects of the piezopotential, created in the InN NW under strain, and the surface quantum states on the transport behavior of charge carriers in different crystal planes of the InN NW were investigated. Regarding the piezotronic properties under applied force, the Schottky barrier height increases in conjunction with the deflection force with high current density at large biases because of tunneling. The strain-induced piezopotential can thus tune the transport process of the charge carriers inside the InN NW over a range larger than that in ZnO. The surface electron accumulation layer is demonstrated to modulate the piezopotential-dependent carrier transport at the metal/InN interfaces. This layer is an important factor in the design of InN-based piezotronic devices and nanogenerators. The output power can be harvested simply by exerting a normal force on a nanogenerator to create piezopotential. The conversion mechanism relies on the coupling between the piezoelectric and semiconducting properties of InN by creating strain fields to drive the charge flow across the NWs. Nanogenerators built using InN NW arrays produce an average output direct current of 205.6 nA by modulating the Schottky barrier height under the influence of the surface electron accumulation layer. The fourth part of this study presents the optimal geometrical design of inertial vibration direct current piezoelectric nanogenerators based on obliquely aligned InN nanowire NW arrays, which exhibited an optimized oblique angle of approximately 58°. The devices have potential applications as sensitive strain sensors and energy harvesting devices capable of gathering energy from mechanical vibrations. The maximal output power density of the nanogenerators is estimated to be 2.9 nW/cm2, which is 3-12 times larger than that of vertically aligned ZnO NW direct current nanogenerators. A serial connection of two nanogenerators exhibited a linear increase in output power, offering enormous potential for the creation of self-powered sustainable nanosystems that use natural ambient energy sources.
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Denker, Christian. "InN and In-rich InGaN Nanocolumns by Molecular Beam Epitaxy." Doctoral thesis, 2011. http://hdl.handle.net/11858/00-1735-0000-0006-B545-F.
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Sardar, Kripasindhu. "Nanostructures And Thin Films Of III-V Nitride Semiconductors." Thesis, 2005. http://etd.iisc.ernet.in/handle/2005/1392.
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