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Desenvolvimento de topologias com redução do processamento redundante de energia para acionamento de leds / Development of topologies with reduced redudant power processing for led drivingCamponogara, Douglas 26 August 2015 (has links)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This work presents the research and development of a connection method for static converters,
called Optimized Cascade, which aims to reduce the redundant power processing in
multiple stage topologies for LED driving. An initial analysis of possible solutions available on
the literature is conducted, where different kinds of solutions are demonstrated, their characteristics
and how they can be classified. Afterward, an analysis of the general characteristics of the
optimized cascade is presented, as well as the method employed to reduce the bus capacitance
value. This reduction aims to replace the electrolytic capacitor for alternative technologies, in
order to increase the lifespan of the LED driver. One of the inovations of this work is the proposal
of a project methodology, focusing the conversion efficiency and the capacitance reduction.
Besides that, a mathematical model of the optimized cascade was derived, so as to establish
the impact of the bus voltage ripple on the LED current. From this model, it has been possible
to determine parameters for choosing the best operating mode for the second stage and the
estimation of capacitance reduction-. Also, some controllers were analyzed to control the PC
stage, on which the resonant controller has been proposed for demanding projects, regarding the
capacitance value and LED current ripple. Finally, two prototypes were mounted and tested,
where an efficiency of thereabout 90% was get with a power factor of 0; 99, along with total
compliance with the power quality parameters and flicker. In both prototypes film capacitors
were employed, contributing to enhance the lifespan of the converter, making it compatible with
LED lifespan. / Este trabalho apresenta o estudo e desenvolvimento de um método de conexão de conversores,
chamado Cascata Otimizada, o qual visa reduzir o processamento redundante de energia
em topologias de múltiplos estágios para acionamento de LEDs. Uma análise preliminar das
soluções disponíveis atualmente na literatura acadêmica é realizada, na qual são demonstrados
diferentes tipos de soluções, suas características e como podem ser classificadas. Em seguida,
uma análise das características gerais da cascata otimizada é apresentada, bem como o método
empregado para redução da capacitância de barramento. Tal redução visa a substituição de capacitores
eletrolíticos por tecnologias alternativas, com o intuito do aumento da vida útil do
driver. Uma das inovações deste trabalho é a proposição uma metodologia de projeto, com
foco na eficiência e na redução da capacitância. Além disso, também foi elaborado um modelo
matemático, de forma a determinar o impacto da ondulação da tensão no barramento sobre a
corrente nos LEDs. A partir desse modelo, foi possível estabelecer parâmetros para a escolha
do melhor modo de operação para o segundo estágio e estimação da redução do capacitor de
barramento. Também foram analisados diversos controladores para o segundo estágio, sendo
proposto o uso do controle ressonante para projetos mais exigentes com respeito ao valor do
capacitor de barramento e da ondulação na corrente de saída. Por fim, dois protótipos foram
montados e testados, obtendo uma eficiência de aproximadamente 90%, fator de potência de
0;99 e total observância aos parâmetros de qualidade de energia e flicker. Em ambos os protótipos
foram empregados capacitores de filme, o que contribui para elevar a vida útil do conversor,
compatibilizando-a com a vida útil da carga LED.
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Controladores de LEDS para iluminação pública com elevado fator de potência comutados no dobro da frequência da rede elétricaNogueira, Fernando José 16 March 2017 (has links)
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Previous issue date: 2017-03-16 / Este trabalho tem como objeto principal a avaliação teórica e experimental do uso de controladores (drivers) comutados no dobro da frequência da rede elétrica, aplicados ao acionamento de luminárias de iluminação pública (IP) empregando diodos emissores de luz, ou LEDs, do inglês Light Emitting Diodes. Inicialmente, o estudo apresenta informações sobre a iluminação pública no Brasil e os novos paradigmas relacionados ao uso dos LEDs nos sistemas de IP. Na sequência, uma revisão bibliográfica sobre drivers para luminárias LED é apresentada. Em seguida, é feita a modelagem matemática de um controlador de LEDs baseado no pré-regulador boost de elevado fator de potência comutado em baixa frequência (120 Hz). Uma metodologia de projeto detalhada é apresentada, sendo aplicada a uma luminária LED de 160 W, que é uma potência típica empregada em iluminação pública. Os resultados experimentais mostram que é possível alcançar elevado fator de potência (0,99), elevado rendimento (95%) e reduzida distorção harmônica total da corrente de entrada (9,4%). Posteriormente, foi realizada a modelagem dinâmica em pequenos sinais e o projeto do controle em malha fechada desse driver. Resultados experimentais mostram que o compensador proposto é capaz de rejeitar distúrbios provenientes da tensão de entrada e da carga, mantendo a corrente nos LEDs no valor de referência. Outras topologias similares também foram exploradas, com destaques para o driver baseado no pré-regulador Ćuk de baixa frequência. Resultados de simulação e resultados experimentais comparam essas topologias entre si, mostrando suas principais vantagens e desvantagens. Como conclusão, a principal contribuição da presente Tese consiste na proposição de topologias de controladores de LEDs empregados em iluminação pública fundamentados em alternativas bastante simples, de baixo custo e elevada vida útil, por dispensarem o uso de capacitores eletrolíticos. Outra contribuição se refere à comprovação de que tais estruturas apresentam conformidade com a norma IEC 61.000-3-2 (2014), classe C, além de corresponderem aos critérios exigidos na norma brasileira NBR 16026 (2012): Dispositivo de controle eletrônico c.c. ou c.a. para módulos de LED - Requisitos de desempenho. / The main purpose of this research is the theoretical and experimental evaluation of the use of drivers switched at twice the frequency of the power grid, applied to street lighting luminaires utilizing light emitting diodes (LEDs). Initially, the study presents information about the street lighting in Brazil and the new paradigms related to the use of LEDs in street lighting systems. Thereafter, a bibliographic review about drivers for LED luminaires is presented. Afterwards, the mathematical modeling of an LED driver based on the high power factor boost pre-regulator switched in low frequency (120 Hz) is shown. A detailed design methodology is presented, applied to a 160 W LED luminaire, which is a usual power level used on street lighting systems. The experimental results show that it is possible to reach high power factor (0.99), high efficiency (95%) and reduced total harmonic distortion of the input current (9.4%). Subsequently, the dynamic modeling in small signals and the control project in closed loop of this driver are performed. Experimental results show that the compensator proposed is capable of rejecting disturbances coming from the input voltage and from the load, keeping the current on the LEDs always at the reference value. Other similar topologies are also examined, highlighting the driver based on the low frequency Ćuk pre-regulator and the quadratic boost pre-regulator. Simulation results and experimental results compare these topologies among themselves, presenting their advantages and disadvantages. As conclusion, the main contribution of this thesis consists is the proposition of topologies of LED drivers used in street lighting luminaires based on very simple circuits, with low cost and long lifetime, because they do not require the use of electrolytic capacitors. Another contribution relates to the corroboration that these structures comply with IEC 61.000-3-2 (2012) class C standard, and correspond to the criteria required in the Brazilian Standard NBR 16026 (2012) standard: Electronic control device c.c. or c.a. for LED modules - Performance requirements.
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The effect of light spectral quality on cryopreservation success of potato (<em>Solanum tuberosum</em> L.) shoot tips <em>in vitro</em>Edesi, J. (Jaanika) 30 April 2018 (has links)
Abstract
Cryopreservation enables storage of genetic resources at ultra-low temperatures (<-150°C) while maintaining viability and regeneration capability. The method is especially suitable for long-term preservation of plant materials that cannot be stored as seeds. The genetic resources of potato (Solanum tuberosum L.), one of the most important food crops in the world, are preserved almost entirely by vegetative preservation. Cryopreservation is therefore increasingly applied for securing potato genetic resources in plant genebanks. A major challenge is, however, that recovery percentages can extensively vary among different genotypes.
Light spectral quality is among the most important factors affecting plant growth and morphogenesis, but its effect with regard to cryopreservation has not been studied. In the present thesis, I studied the effect of six different light qualities on cryopreservation success of five potato cultivars before and after cryopreservation. I also explored how the different light conditions affect gene transcript abundance of recovering potato shoot tips.
The results indicate that light spectral quality significantly affects the cryopreservation success of potato shoot tips in vitro. Prior to cryopreservation, cultivation under blue LEDs resulted in high initial survival, while post-cryopreservation exposure to a combination of red and blue LEDs (90% red, 10% blue) doubled the regeneration percentages. Concurrently, for most cultivars, red LEDs had adverse effects both before and after cryopreservation.
The transcriptome analysis of potato shoot tips revealed the complex and extensive effect of cryopreservation on transcript abundance. Moreover, the expression level of stress- and defence-responsive genes was affected by light spectral quality. The positive effect of red-blue LEDs on shoot formation could tentatively be associated with a higher level of morphogenesis-related transcripts and lower level of stress and defence-responsive transcripts. The present thesis reveals that light spectral quality is an additional non-cryogenic factor, which can significantly increase the cryopreservation efficiency of plant germplasm. / Tiivistelmä
Syväjäädytys mahdollistaa geenivarojen säilytyksen erittäin alhaisissa lämpötiloissa (<-150°C), siten että niiden elin- ja uusiutumiskyky säilyvät. Menetelmä soveltuu erityisesti sellaisten kasvimateriaalien pitkäaikaissäilytykseen, joita ei voida säilöä siementen avulla. Peruna (Solanum tuberosum L.) on yksi maailman tärkeimmistä ruokakasveista ja sen geenivaroja säilytetään lähes pelkästään vegetatiivisesti. Syväjäädytysmenetelmää käytetäänkin kasvavissa määrin perunan geenivarojen taltioimiseen geenipankeissa. Haasteena on kuitenkin syväjäädytyksen jälkeinen suuri vaihtelu elpymisprosenteissa eri genotyyppien välillä.
Valon laatu on yksi tärkeimmistä kasvien kasvuun ja kehitykseen vaikuttavista tekijöistä, mutta sen vaikutusta syväjäädytyksen yhteydessä ei ole tutkittu. Väitöskirjassani tutkin kuuden erilaisen valonlaadun vaikutusta sekä syväjäädytystä edeltävän että sen jälkeisen kasvatuksen aikana viiden perunalajikkeen selviytymiseen. Lisäksi tutkin, miten erilaiset valo-olosuhteet vaikuttivat geenien ilmenemiseen elpyvissä perunan versonkärjissä.
Tutkimukseni osoitti, että valon laatu vaikuttaa merkittävästi perunan versonkärkien kykyyn elpyä syväjäädytyksestä in vitro -olosuhteissa. Kun perunan versonkärkiä kasvatettiin sinisten LED-valojen alla ennen syväjäädytystä, niiden elävyysprosentit olivat korkeita, kun taas syväjäädytystä seuraava kasvatus sinipunaisten LED-valojen (90 % punaista, 10 % sinistä) alla kaksinkertaisti uusiutumisprosentit. Samanaikaisesti suurimmalle osalle lajikkeista punaisilla LED-valoilla oli epäsuotuisat vaikutukset selviytymiseen sekä syväjäädytystä edeltävän, että sitä seuraavan kasvatuksen aikana.
Perunan kärkisilmujen geeniekspressioanalyysi osoitti, että syväjäädyttäminen aiheuttaa laajoja ja monitahoisia vaikutuksia kasvin geenien toiminnassa. Valon laatu vaikutti erityisesti stressi- ja puolustusgeenien ilmenemiseen. Tulokset viittaavat siihen että sinipunaisten LED-valojen uusiutumista edistävä vaikutus voi liittyä morfogeneesissä toimivien geenituotteiden runsauteen ja toisaalta stressi- ja puolustusgeenituotteiden määrän laskuun. Kaiken kaikkiaan tutkimukseni osoitti, että valon laatu on tärkeä ei-kryogeeninen tekijä, joka voi lisätä kasvien syväjäädytyksen tehokkuutta.
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Detekce živosti prstu pomocí osvětlení různé vlnové délky / Liveness Finger Detection by LEDs with Different WavelengthsMalý, Tomáš January 2013 (has links)
The goal of this thesis was to study biometrics and focus on liveness detection. Design liveness detection for existing sensor with LEDs using different wavelength.
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Industrial Symbiosis of Vertical Hydroponic Farming System at SweGreen / Industriell symbios av vertikala hydroponiska jordbrukssystem på SweGreenFarkhondehmonfared, Narmin January 2022 (has links)
The United Nations projects that by the year 2050, there will be as many as 9.7 billion people on earth (UN, 2019). Along with the world population growth, the demand for food production will be increased. On the other side, agriculture plays a crucial role in global warming, increasing food production challenges. Thus, more sustainable methods should be chosen to respond to population demand and decrease the impact of agricultural activities on climate change. One of these alternative methods is Urban farming, specifically hydroponic vertical farming, in which the food is produced indoors under exceptional conditions as using artificial lighting and less water. Hydroponic vertical farming has several benefits, higher production per area, a controlled environment, less land usage, less water consumption, etc. Vertical farms use LEDs as lightning sources to help photosynthesis; LEDs produce a massive amount of excess heat, which will be released to the environment and impact global warming. Therefore, a solution should be found to use the excess heat for other purposes instead of releasing it into the environment. In this study, the environmental performance of SweGreen’s hydroponic vertical farm will be assessed using a Life cycle assessment. The SweGreen hydroponic farm is located in a basement of a host building in Stockholm, Sweden. There is a symbiotic network between the farm and the host building where the farm provides the building with excess heat produced from the LEDs and, in return, gains carbon dioxide from the building. The result of this study shows that symbiotic network can decrease the impact of agriculture and excess produced heat, where the required heat for the building will be replaced from district heating by the produced excess heat. The symbiotic development between the host building and the farm will benefit the farm in various aspects and highlights the importance of urban symbiosis to reduce the impacts. / Enligt prognoser av Förenta Nationerna ska leva 9.7 billion människor på jorden till och med 2050 (FN, 2019). Världens befolkningstillväxt orsakar ökade efterfrågningar på livsmedelsproduktion. Tillsammans med de här ökade efterfrågningarna behov av jordbruk och dess produktioner ska ökas. De ökningarna skaffar seriösa utmaningar och oror Global uppvärmning. Därför behöver världen nya hållbara metoder att kunna hitta bra lösningar som minskas sådana påverkningar på klimatförändringarna. En av de nya hållbara metoderna är Urban Farming och speciellt hydroponiskt vertikalt jordbruk. Med denna metod livsmedel produceras inomhus med hjälpen av konstgjord belysning. Under de kontrollerade situationer ska mötas högre produktion per område och mindre vattenkonsumtion. Lysdioder (LEDs) bidrar behov av belysning för fotosyntesprocess i Vertikal Farms. Dock släpper LEDs ut en enorm mängd överskottsvärme i miljön som har en direkt påverkan på globala uppvärmningen. En bra lösning för detta problem är att hittas ett sätt att använda överskottsvärmen för andra ändamål. I den här studien ska granskas miljöprestandan för SweGreen’s hydroponic vertikal farm med hjälp av en livscykelanalys. Gården ligger i Stockholm, Sverige. Det finns ett symbiotiskt nätverk mellan gården och vårdbyggnaden där levereras LEDs överskottsvärmen för byggnaden och fås koldioxid från den. Resultatet av denna studie provar att symbiotiska nätverken kan minska påverkan av producerad överskottsvärmen på klimatförändringarna och Global uppvärmning.Symbiotiska utvecklingen mellan vårdbyggnaden och gården är intressant från olika aspekter och är viktig att minska påverkningarna på miljön.
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Conversor integrado SEPIC buck-boost aplicado ao acionamento de LEDs de potência em iluminação públicaAlmeida, Pedro Santos 23 March 2012 (has links)
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Previous issue date: 2012-03-23 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Este trabalho apresenta um estudo acerca da alimentação de diodos emissores de luz (LEDs) a
partir da rede elétrica empregando conversores eletrônicos com correção do fator de potência.
O estudo visa o desenvolvimento de um conversor que pode ser aplicado em iluminação
pública, que atenda às demandas típicas de alto fator de potência, alta eficiência, reduzido
número de componentes, baixa distorção harmônica da corrente de entrada e possa atingir
uma elevada vida útil, através da substituição de capacitores eletrolíticos no circuito de
potência por capacitores de filme. É proposta uma nova topologia de conversor para
implementar tal acionamento, baseado em uma integração entre dois estágios, que passam a
compartilhar um único interruptor estático. Os conversores SEPIC e buck-boost operando em
modo de condução descontínua (DCM) são escolhidos para compor cada um destes estágios,
atuando o primeiro na correção do fator de potência e o segundo na regulação de corrente na
carga. Uma metodologia de projeto que visa excluir os capacitores eletrolíticos é
desenvolvida, partindo de dados fotométricos que permitem aplicar nos LEDs uma ondulação
limite de 50% em amplitude, sem causar prejuízos ao seu desempenho fotométrico. Um
protótipo de 70 W é apresentado, cujos resultados experimentais demonstram alto fator de
potência (0,998), baixa distorção harmônica de corrente (3,2%) e alta eficiência (90,2%),
enquanto empregando somente capacitores de filme metalizado, de longa vida útil, no circuito
de potência. Uma abordagem das possibilidades de se implementar um controlador digital
para o novo conversor proposto é feita, partindo de um modelo de pequenos sinais para o
conversor operando em DCM. / This work presents a study regarding the feeding of light-emitting diodes (LEDs) from mains
(grid power) employing electronic drivers with power factor correction. The study aims the
development of an LED driver which can be applied to public and street lighting, complying
with the typical demands of high power factor, high efficiency, reduced component count,
low total harmonic distortion (THD) of input current and which can attain long lifespan,
through the substitution of electrolytic capacitors within the power circuit by film capacitors.
It is proposed a new converter topology to implement such driver, based on an integration
between two stages which share a common static power switch. The SEPIC and buck-boost
converters operating in discontinuous conduction mode (DCM) are chosen to make up each of
these two stages, the first acting as a power factor corrector and the second as a load currentcontrolling
stage. A design methodology which aims the exclusion of electrolytic capacitors is
developed, stemming from photometric data which allow the LEDs to be operated with
current ripples up to 50% in amplitude, without causing any harm to their photometric
performance. A 70 W prototype is presented, whose experimental results demonstrate high
power factor (0.998), low current harmonic distortion (3.2%) and high efficiency (90.2%),
while employing only long-life metallised-film capacitors on the power circuit. An approach
to the possibilities of implementing a digital controller for the proposed novel converter is
done, starting from a small-signal model for the converter operating in DCM.
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Metodologia de projeto eletrotérmico de LEDs aplicada ao desenvolvimento de sistemas de iluminação pública / LED electrothermal design methodology applied to a street lighting systemBender, Vitor Cristiano 23 July 2012 (has links)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This work presents an LED electrothermal design methodology applied to a street
lighting system. The methodology aims to provide indicatives of the optimal LED operating
point for lighting systems design, considering electrical, thermal and photometric system
features. Different projects are developed according to the methodology, the theoretical
results are compared with fluid dynamics simulation and demonstrated by experimental
results. A research including luminous flux, luminous efficacy and flicker is performed
considering the LED current ripple, defining acceptable levels of ripple based on the optimal
operational point. The methodology is applied by developing a lighting system composed of
an LED driver and a thermal dissipation system, comprising a luminaire, a heatsink and fans.
The lighting system includes electrothermal feedback control. The results provide high power
factor with low current harmonic distortion to the power grid. The LED operational
temperature ensures the luminous flux maintenance over the system lifetime. / Este trabalho apresenta uma metodologia de projeto eletrotérmico de LEDs aplicada a
um sistema de iluminação pública. A metodologia tem o objetivo de proporcionar indicativos
do melhor ponto de operação do LED para o projeto de sistemas de iluminação, considerando
os aspectos elétricos, térmicos e fotométricos envolvidos no sistema. Diferentes projetos são
desenvolvidos utilizando a metodologia, os resultados teóricos obtidos são comparados com
simulações computacionais de dinâmica dos fluidos e comprovados através de resultados
experimentais. Um estudo do fluxo, eficácia e cintilação luminosa é também realizado
considerando a ondulação de corrente aplicada aos LEDs, definindo os níveis aceitáveis de
ondulação com base no ponto ótimo de operação. Para aplicação da metodologia é
desenvolvido um sistema de iluminação pública composto por um circuito de acionamento
dos LEDs e um sistema de dissipação térmica, formado por uma luminária, um dissipador de
calor e ventiladores. O sistema de iluminação possui controle com realimentação
eletrotérmica. Os resultados obtidos proporcionam alto fator de potência com baixa distorção
harmônica ao sistema elétrico e temperatura de operação que garante a manutenção do fluxo
luminoso dos LEDs durante toda a vida útil do sistema.
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Light Management in Photovoltaic Devices and Nanostructure Engineering in Nitride-based Optoelectronic DevicesHan, Lu 02 June 2017 (has links)
No description available.
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Growth and characterization of non-polar GaN materials and investigation of efficiency droop in InGaN light emitting diodesNi, Xianfeng 06 August 2010 (has links)
General lighting with InGaN light emitting diodes (LEDs) as light sources is of particular interest in terms of energy savings and related environmental benefits due to high lighting efficiency, long lifetime, and Hg-free nature. Incandescent and fluorescent light sources are used for general lighting almost everywhere. But their lighting efficiency is very limited: only 20-30 lm/W for incandescent lighting bulb, approximately 100 lm/W for fluorescent lighting. State-of-the-art InGaN LEDs with a luminous efficacy of over 200 lm/W at room temperature have been reported. However, the goal of replacing the incandescent and fluorescent lights with InGaN LEDs is still elusive since their lighting efficiency decreases substantially when the injection current increases beyond certain values (typically 10-50 Acm-2). In order to improve the electroluminescence (EL) performance at high currents for InGaN LEDs, two approaches have been undertaken in this thesis. First, we explored the preparation and characterization of non-polar and semi-polar GaN substrates (including a-plane, m-plane and semi-polar planes). These substrates serve as promising alternatives to the commonly used c-plane, with the benefit of a reduced polarization-induced electric field and therefore higher quantum efficiency. It is demonstrated that LEDs on m-plane GaN substrates have inherently higher EL quantum efficiency and better efficiency retention ability at high injection currents than their c-plane counterparts. Secondly, from a device structure level, we explored the possible origins of the EL efficiency degradation at high currents in InGaN LEDs and investigated the effect of hot electrons on EL of LEDs by varying the barrier height of electron blocking layer. A first-order theoretical model is proposed to explain the effect of electron overflow caused by hot electron transport across the LED active region on LED EL performance. The calculation results are in agreement with experimental observations. Furthermore, a novel structure called a “staircase electron injector” (SEI) is demonstrated to effectively thermalize hot electrons, thereby reducing the reduction of EL efficiency due to electron overflow. The SEI features several InyGa1-yN layers, with their In fraction (y) increasing in a stepwise manner, starting with a low value at the first step near the junction with n-GaN.
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Microstructural characterisation of novel nitride nanostructures using electron microscopySevers, John January 2014 (has links)
Novel semiconductor nanostructures possess a range of notable properties that have the potential to be harnessed in the next generation of optical devices. Electron microscopy is uniquely suited to characterising the complex microstructure, the results of which may be related to the growth conditions and optical properties. This thesis investigates three such novel materials: (1) GaN/InGaN core/shell nanowires, (2) n-GaN/InGaN/p-GaN core/multi-shell microrods and (3) Zn<sub>3</sub>N<sub>2</sub> nanoparticles, all of which were grown at Sharp Laboratories of Europe. GaN nanowires were grown by a Ni-catalysed VLS process and were characterised by various techniques before and after InGaN shells were deposited by MOCVD. The majority of the core wires were found to have the expected wurtzite structure and completely defect free – reflected in the strong strain-free photoluminescence peak –with a- and m- axis orientations identified with shadow imaging. A small component, <5%, were found to have the cubic zinc-blende phase and a high density of planar faults running the length of the wires. The deposited shells were highly polycrystalline, partially attributed to a layer of silicon at the core shell interface identified through FIB lift-out of cross section samples, and accordingly the PL was very broad likely due to recombination at defects and grain boundaries. A high throughput method of identifying the core size indirectly via the catalyst particle EDX signal is described which may be used to link the shell microstructure to core size in further studies. An n-GaN/InGaN/p-GaN shell structure was deposited by MOCVD on the side walls of microrods etched from c-axis GaN film on sapphire, which offers the possibility of achieving non-polar junctions without the issues due to non-uniformity found in nanowires. Threading dislocations within the core related to the initial growth on sapphire were shown to be confined to this region, therefore avoiding any harmful effect on the junction microstructure. The shell defect density showed a surprising relationship to core size with the smaller diameter rods having a high density of unusual 'flag' defects in the junction region whereas the larger diameter sample shells appeared largely defect free, suggesting the geometry of the etched core has an impact on the strain in the shell layers. The structure of unusual 'flag' defects in the m-plane junctions was characterised via diffraction contrast TEM, weak beam and atomic resolution ADF STEM and were shown to consist of a basal plane stacking faults meeting a perfect or partial dislocation loop on a pyramidal plane, the latter likely gliding in to resolve residual strain due to the fault formed during growth. Zn<sub>3</sub>N<sub>2</sub> has the required bandgap energy to be utilised as a phosphor with the additional advantage over conventional materials of its constituent elements not being toxic or scarce. The first successful synthesis of Zn<sub>3</sub>N<sub>2</sub> nanoparticles appropriate to this application was confirmed via SAD, EDX and HRTEM, with software developed to fit experimental polycrystalline diffraction patterns to simulated components suggesting a maximum Zn<sub>3</sub>N<sub>2</sub> composition of ~30%. There was an apparent decrease in crystallinity with decreasing particle size evidenced in radial distribution function studies with the smallest particles appearing completely amorphous in 80kV HRTEM images. A rapid change in the particles under the electron beam was observed, characterised by growth of large grains of Zn<sub>3</sub>N<sub>2</sub> and ZnO which increased with increasing acceleration voltage suggesting knock-on effects driving the change. PL data was consistent with the bandgap of Zn<sub>3</sub>N<sub>2</sub> blue shifted from 1.1eV to around 1.8eV, confirming the potential of the material for application as a phosphor.
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