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Newsham, David K. Sen Ayusman. "Palladium catalyzed copolymerizations of polar and non-polar monomers." [University Park, Pa.] : Pennsylvania State University, 2009. http://etda.libraries.psu.edu/theses/approved/WorldWideIndex/ETD-4528/index.html.
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Hanan, Faridah Hanim Ab. "Plasticizer transportation studies in polar and non-polar rubbers." Thesis, London Metropolitan University, 2001. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341733.
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SILVA, ELIZANDRA MARTINS. "NANOSCALE MECHANICAL DEFORMATION MECHANISMS OF POLAR AND NON-POLAR ZNO." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2014. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=24779@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
PROGRAMA DE SUPORTE À PÓS-GRADUAÇÃO DE INSTS. DE ENSINO
Neste trabalho foi estudado o mecanismo de deformação de faces polares e não polares do óxido de zinco (ZnO), através da introdução de defeitos mecânicos por nanoindentação. A estrutura cristalina estável do ZnO é do tipo wurtzita, de forte caráter anisotrópico já observado em relação a propriedades como piezoeletricidade e polarização espontânea. O mecanismo de deformação mecânica desses sistemas ainda não está bem esclarecido e são de vital importância na otimização de dispositivos optoeletrônicos. A extensão dos defeitos para cada orientação do cristal foi analisada via microscopia eletrônica de transmissão e correlacionada com o movimento de planos basais {0001} de forma divergente, em faces não polares (1100) e (1120), e ao movimento de planos piramidais {1011} de forma convergente para faces polares (0001) e (0001). A extensão da deformação induzida abaixo da superfície foi avaliada, onde foi possível identificar a formação de discordâncias do tipo parafuso que se propagam através do sistema de escorregamento (1120)(0001), se propagando de forma altamente localizada abaixo da superfície. O início da deformação plástica em monocristais é marcado por eventos plásticos súbitos (pop-ins). Estes eventos foram identificados e analisados em função da força e da extensão da deformação gerada. A topografia e forma das impressões residuais foi analisada usando microscopia de força atômica. Os defeitos observados no plano superficial tenderam a se propagar em direções preferenciais num processo induzido pela formação de zonas de tensão em torno da indentação. A formação de zonas de tensão trativa em uma dada direção aumenta a mobilidade das discordâncias, enquanto zonas de tensão compressiva agem contribuindo para o travamento. Estas zonas foram identificadas e a magnitude desta tensão foi estimada via catodoluminescência. Observamos também que a face polar (0001) apresentou um comportamento reativo, onde defeitos localizados abaixo da superfície foram revelados através do processo de limpeza.
In this work, deformation mechanisms of polar and non-polar zinc oxide (ZnO) were studied by nanoindentation tests. The stable crystal structure of ZnO is the wurtzite with a strong anisotropic character observed in relation to the piezoelectricity and spontaneous polarization properties, for example. The mechanical deformation mechanisms of these sorts of materials are not yet fully understood, being of vital importance for optoelectronic devices optimization.For each ZnO crystallographic orientation, the induced defects damages were analyzed by transmission electron microscopy (TEM) and correlated with the slip of basal planes {0001} in the divergent directions for the both non-polar faces (1100) and (1120), as well as for the both polar faces (0001) and (0001). Screw perfect dislocations were identified by propagating through the slip system (1120)(0001). The beginning of plastic deformation in single crystals is marked by pop-ins events. Such events were identified and analyzed in function of the applied force and size. The residual impressions topography and shape were analyzed by atomic force microscopy (AFM). The observed defects on the surface were propagated in a preferred direction induced by stress components around the indentation. Tensile stress generation in a certain direction increases the dislocations mobility, while compressive stress contributes to pinning regions. Stress components were identified and their magnitudes were estimated by cathode luminescence method. The polar face (0001) showed a reactive behavior; some defects produced underneath the surface were revealed by samples cleaning process.
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Persson, Marcus. "Surfactants at non-polar surfaces." Doctoral thesis, KTH, Chemistry, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3444.
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The aim of this thesis work was to investigate theadsorption of surfactants to different nonpolar interfaces.Particularly, the effects of the polar group and the nature ofthe hydrophobic interface were elucidated. The interfacialbehavior of the liquid-vapor interface was investigated bymeans of surface tension measurements. Here the effect of thepolar group and the hydrocarbon chain length was investigatedin a systematic manner. It was found that the shorter of thetwo chains examined, decyl, generated a larger surface pressurecontribution than the longer, dodecyl. Furthermore, the sugarbased surfactants behaved differently as compared to theethylene oxide based ones. The former could be modelled byassuming a hard disc behavior of the head group while thelatter displayed polymeric behavior. The influence of saltconcentration on the surface tension behavior of an ionicsurfactant, sodium dodecyl sulphate, was investigated. Theresult could be rationalized by employing the Gouy- Chapmanmodel to the polar region. Furthermore, mixtures of two sugarbased surfactants were investigated by surface tensionmeasurements and the adsorbed amount of the two components atthe interface atdifferent concentrations and fractions in thebulk were obtained by applying the Gibbs surface tensionequation. It was found that the molecule with the smaller headgroup adsorbed preferentially, and more so as the totalsurfactant concentration was increased. These findings could beexplained by considering the interactions generated by thedifferent head groups. The adsorption of sugar surfactants toan isolated hydrophobic surface was studied by means of wettingmeasurements and the behavior was similar to that at theliquid-vapor interface. Wetting isotherms were measured on twodifferent hydrophobic surfaces where the covalently attachedhydrophobic layers were in a crystalline and fluid state,respectively. The wetting results revealed that the sugarsurfactants anchored in the fluid hydrophobic layer. This had asignificant influence on the force profile. For example, at thecrystalline surface the surfactant monolayers were easilyremoved as the surface came into contact at relatively lowapplied loads. This was not the case when the hydrophobic layerwas in a fluid state. Here a significant fraction of thesurfactants remained between the surfaces. Disjoining pressureisotherms were measured using a sugar based surfactant thatwere thoroughly purified and compared to the as receivedsample. Even the purified sample showed a double-layer forcealthough lower as compared to the as received, one. Asignificant difference in foam stability was also observed.
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Tabor, Richard F. "Surfactant kinetics in non-polar solvents." Thesis, University of Bristol, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.508096.
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Chang, Tse Yang. "Characterisation of polar (0001) and non-polar (11-20) ultraviolet nitride semiconductors." Thesis, University of Cambridge, 2012. https://www.repository.cam.ac.uk/handle/1810/242371.
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UV and deep-UV emitters based on AlGaN/AlN heterostructures are very inefficient due to the high lattice mismatch of these films with sapphire substrates, leading to high dislocation densities. This thesis describes the characterisation of the nanostructures of a range of UV structures, including c-plane (polar) AlGaN epilayers grown on AlN template, and nonpolar GaN/AlGaN MQWs grown on a-plane GaN template. The results are based primarily on transmission electron microscopy (TEM), cathodoluminescence in the scanning electron microscope (SEM-CL), high-resolution X-ray diffraction (HRXRD) and atomic force microscopy (AFM) measurements. The structural and optical properties of various types of defect were examined in the c-plane AlGaN epilayers. Strain analysis based on in-situ wafer curvature measurements was employed to describe the strain relief mechanisms for different AlGaN compositions and to correlate the strain to each type of defect observed in the epilayers. This is followed by the investigation of AlN template growth optimisation, based on the TMA pre-dose on sapphire method to enhance the quality and the surface morphology of the template further. The initial growth conditions were shown to be critical for the final AlN film morphology. A higher TMA pre-dose has been shown to enable a better Al coverage leading to a fully coalesced AlN film at 1 μm thickness. An atomically smooth surface of the template was achieved over a large 10 x 10 μm AFM scale. Finally, the investigation of UV emitters based on nonpolar crystal orientations is presented. The SiNx interlayer was able to reduce the threading dislocation density but was also found to generate voids with longer SiNx growth time. The relationship between voids, threading dislocations, inversion domain boundaries and their associated V-defects and the variation in MQW growth rate has been discussed in detail.
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El-Agamey, Ali Abdel Ghani. "Acylperoxyl radicals and their reactions with carotenoids in polar and non-polar solvents." Thesis, Keele University, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.252583.
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Emery, Robert Michael. "Investigation into the growth of non-polar and semi-polar InGaN quantum dots." Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.708911.
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Johnston, C. F. "Characterization of (11-20) non-polar and (11-22) semi-polar GaN epitaxial films." Thesis, University of Cambridge, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.605657.
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This thesis describes the microstructural characterization (using transmission electron microscopy [TEM], high resolution X-ray diffraction [HRXRD] and atomic force microscopy [AFM]) of non-polar (11-20) and semi-polar (11-22) GaN epitaxial layers. They were grown under a range of conditions on sapphire by metal-organic vapour phase epitaxy (MOVPE). The majority of the dislocations were partial dislocations bounding BSFs. As a consequence, defects were confined to the c-plane. A 3D-2D growth transition (where 3D islands are grown initially, then coalesced) reduced the defect density of non-polar GaN. Optimised coalescence conditions (i.e. a V/III ratio of 50) produced smooth films with a low RMS roughness. The effect of a 3D-2D growth transition on semi-polar material was less clear, but the microstructure was similar to non-polar GaN, in that the majority of dislocations were partials bounding BSFs. Since the growth conditions for the semi-polar epilayers were not optimised, surfaces were rough. Quantum wells grown on these templates were found to follow the surface roughness resulting in large fluctuations in quantum well width (of a few nanometres) and subsequent broadening of peaks in the photoluminescence spectra. To reduce the defect density, epitaxial laterial overgrowth (ELOG), SiNx interlayers and ScN interlayers were applied to non-polar and semi-polar films. ELOG was effective at reducing both BSF and dislocation density in both examples. Thick SiNx interlayers in non-polar GaN reduced dislocation density by a factor of 500 and BSF density by a factor of 5, compared to the template. An 8.5 nm ScN interlayer in semi-polar GaN reduced the dislocation density by a factor of 200 and BSF density by a factor of 14.
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Derry, Matthew J. "Polymerisation-induced self-assembly in non-polar solvents." Thesis, University of Sheffield, 2016. http://etheses.whiterose.ac.uk/13620/.
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This Thesis describes the reversible addition-fragmentation chain transfer (RAFT) dispersion polymerisation of benzyl methacrylate (BzMA) in non-polar solvents. Firstly, oil-soluble poly(lauryl methacrylate) (PLMA), poly(stearyl methacrylate) (PSMA) and poly(behenyl methacrylate) (PBhMA) macromolecular chain transfer agents (macro-CTAs) are synthesised via RAFT solution polymerisation in toluene. These macro-CTAs are then chain-extended in turn with varying amounts of BzMA in industrially-sourced mineral oil or a poly(α-olefin). Polymerisation-induced self-assembly (PISA) occurs under these conditions, where the soluble BzMA monomer polymerises to form an insoluble poly(benzyl methacrylate) (PBzMA) block, thus driving the in situ formation of spheres, worms or vesicles. Subtle differences in the phase diagrams constructed for PLMA-PBzMA diblock copolymer nano-objects are observed in different solvents. In such PISA formulations, the stabiliser block DP is an important parameter, because only kinetically-trapped spheres are accessible when sufficiently long stabilisers (e.g. PLMA39, PSMA18 or PBhMA37) are used. PLMA47-PBzMA100 spheres could be prepared at copolymer concentrations up to 50% w/w solids. Importantly, a highly convenient ‘one-pot’ synthetic protocol was developed, whereby 39 nm PLMA50-PBzMA100 spheres were prepared at 30% w/w solids within 9 h starting from LMA monomer. The phase diagram for PSMA13-PBzMAx diblock copolymer nanoparticles in mineral oil indicates that the final copolymer morphologies are only weakly dependent on copolymer concentration, which enables the synthesis of pure spheres, worms or vesicles at just 5.0% w/w solids. This facilitated in situ small-angle X-ray scattering (SAXS) studies during the PISA synthesis. When targeting PSMA31-PBzMA2000 spheres, the PBzMA core diameter and aggregation number per sphere (Ns) increased monotonically during the polymerisation. When targeting PSMA13-PBzMA150 vesicles, the full range of morphologies is observed, from soluble copolymer chains to the final vesicles via intermediate spheres and worms. Transmission electron microscopy (TEM) studies indicated that vesicles are formed from worms via transient octopi and jellyfish morphologies, which is consistent with observations previously reported for aqueous PISA formulations. A combination of dynamic light scattering (DLS), TEM and both in situ and post mortem SAXS analyses confirmed that the overall vesicle dimensions are conserved as the membrane thickens, which indicates an ‘inward growth’ mechanism. This is consistent with observations recently reported for an aqueous PISA formulation and hence suggests a universal vesicle growth mechanism for all PISA formulations. Dispersions of PSMA13-PBzMA65 worms form free-standing gels at 20 °C due to multiple inter-worm contacts, but heating leads to surface plasticisation. This induces a worm-to-sphere transition and concomitant degelation, since isotropic spheres cannot form inter-particle contacts at this copolymer concentration. The worm-to-sphere transition was characterised using TEM, DLS and rheology.
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Schoeler, Andreas Martin. "Charge of water droplets in non-polar oils." Thesis, King's College London (University of London), 2015. http://kclpure.kcl.ac.uk/portal/en/theses/charge-of-water-droplets-in-nonpolar-oils(583a7eea-71c6-4499-a15a-f421d6e681f6).html.
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Water-in-oil microdroplets are an attractive “tool” in lab-on-a-chip devices, as they offer simple compartmentalisation, constitute tiny reaction chambers and can be used to perform “digital” operations. One of the many benefits they offer is the ability to manipulate droplets by electric fields, which can be implemented on-chip, using electrodes and suitable wiring. Water droplets dispersed in a non-polar oil are manipulated by exploiting the fundamental phenomenon of electrophoretic motion, i.e. motion in response to an external, electric field. There are surprisingly little data regarding the electrophoretic mobility of water droplets dispersed in a non-polar oil and this work aims to elucidate some of the properties of droplet charge from measurements of the electrophoretic mobility of individual water droplets in two different, non-polar oils of similar, physical fluid properties: silicone and paraffin oil. Single droplets of varying pH and ion concentrations were investigated and it was found that the effective initial droplet charge (i.e. the charge a water droplet has before making contact with a biased electrode) is always positive and independent of pH and ion concentration. When the anionic surfactant SDS (Sodium Dodecyl Sulfate) was dispersed in the water phase, the initial droplet charge could be altered from positive to negative at concentrations greater than 1 g/l. However, using cationic surfactant CTAB (Hexadecyltrimethyl Ammonium Bromide) had no impact on droplet surface charge. Once the droplet touches a biased electrode, the droplet charge in increased by a factor of 10 and any surfactant charge effects are overridden. Lastly, complex oil-in-water-in-oil and water-in-oil-in-water-in-oil droplets were created and their electrophoretic mobility was studied. It was found that the inner droplet does not affect electrophoretic motion of the core shell drop, regardless of size and composition, nor does it experience the same (if any) electric field strength the outer water shell is subjected to. This is advantageous in a variety of applications. For example, oil droplets of varying types and sizes could accurately be transported and manipulated at the same speed using monodisperse water shells, which can be either thick or ultrathin. This could also be used for the manipulation of materials that would otherwise be damaged by an electrical field.
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Nowack, Rüdiger Jens. "Neutral nickel and palladium complexes as catalysts in copolymerizations of polar and non-polar monomers." [S.l. : s.n.], 2008. http://nbn-resolving.de/urn:nbn:de:bsz:289-vts-63659.
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Pearcy, Adam C. "Non-covalent and covalent interactions between phenylacetylene and quinoline radical cations with polar and non-polar molecules in the gas phase." VCU Scholars Compass, 2019. https://scholarscompass.vcu.edu/etd/5990.
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Gas phase molecular clusters present an ideal medium for observing factors that drive chemical reactions without outside interferences from excessive solvent molecules. Introducing an ion into the cluster promotes ion-molecule interactions that may manifest in a variety of non-covalent or even covalent binding motifs and are of significant importance in many fields including atmospheric and astronomical sciences. For instance, in outer space, molecules are subject to ionizing radiation where ion-molecule reactions become increasingly competitive to molecule-molecule interactions. To elucidate individual ion-molecule interaction information, mass spectrometry was used in conjunction with appropriate theoretical calculations.
Three main categories of experiment were conducted in this dissertation. The first of which were thermochemical equilibrium measurements where an ion was introduced to an ion mobility drift cell wherein thermalizing collisions occur with helium buffer gas facilitating a reversible reaction with a neutral molecule allowing the standard changes in enthalpy and entropy to be determined. The second type of experiment was an ion mobility experiment where an ionized homo- or hetero-cluster was injected into the drift cell at specific conditions allowing the reduced mobility and collisional cross-section to be evaluated. Thirdly, kinetics measurements were taken following injection of an ion into the drift cell were an irreversible reaction ensued with the neutral species hindering equilibrium, but prompting rate constant assessment.
Previous research has laid the groundwork for this dissertation as the results and discussion contained herein will build upon existing data while maintaining originality. For example, past work has given support for ion-molecule reactions involving precursor species such as acetylene and hydrogen cyanide to form more complex organics, perhaps leading to biologically relevant species. The chemical systems studied for this research are either ionized substituted benzenes like phenylacetylene and benzonitrile or polycyclic aromatic nitrogen-containing hydrocarbons like quinoline and quinoxaline interacting with a variety of neutral species.
Hydrogen bonding and its many sub-sections are of the utmost importance to the kinds of reactions studied here. Past work has shown the tendency of organic radical cations to form conventional and unconventional ionic hydrogen bonds with gas phase solvents. Other non-covalent modes of interaction have also been detected in addition to the formation of covalently bound species. Gas phase reactions studied here will explore, via mass-selected ion mobility, reversible and irreversible reactions leading to binding enthalpy and entropy and rate constant determination, respectively, in addition to collisional cross-section determination.
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Gunkel, Felix [Verfasser]. "The role of defects at functional interfaces between polar and non-polar perovskite oxides / Felix Gunkel." Aachen : Hochschulbibliothek der Rheinisch-Westfälischen Technischen Hochschule Aachen, 2013. http://d-nb.info/1044492325/34.
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Bennett, Megan. "Energy Transfer Dynamics in Collisions of Polar and Non-polar Gases with Functionalized Self-Assembled Monolayers." Thesis, Virginia Tech, 2007. http://hdl.handle.net/10919/33229.
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Molecular beam scattering experiments are used to investigate the extent of thermal accommodation of Ne, CD4, ND3, and D2O in collisions with long chain CH3, NH2, and OH terminated self-assembled monolayers (SAMs) on gold. Surface rigidity, internal degrees of freedom of the impinging gas, and potential energy surface well depths have been explored as a way to predict the outcome of a gas-surface collision. Ne is used to assess the mechanical rigidity of the SAMs. The order of rigidity is CH3 < NH2 ~ OH. The NH2 and OH terminated SAMs are more rigid due to the intermolecular hydrogen bonding structure at the gas-surface interface. Despite the hydrogen bonding nature of the NH2 and OH terminated SAMs CD4, ND3, and D2O are extensively thermally accommodated on the surfaces, therefore surface rigidity is no solely responsible for energy transfer dynamics. It was found that the number of degrees of freedom do not predict how extensively a gas will thermally accommodate on a surface capable of hydrogen bonding. A qualitative correlation between increasing potential energy well depths and the extent of thermal accommodation has been established as a result of these scattering experiments.Master of Science
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Gong, Yipin. "MOCVD growth and optical investigation of III-nitride materials including non-polar and semi-polar GaN." Thesis, University of Sheffield, 2014. http://etheses.whiterose.ac.uk/4991/.
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This thesis focuses on the growth of high quality III-nitride materials by MOCVD along both c-direction and non-polar a-direction. High temperature AlN buffer layer is introduced, which can effectively reduce the dislocation density of the overlying layer. Stimulated emission at 340nm has been obtained by such AlN buffer techniques, which mechanism is understood by studying the strain relaxation in the QW structure with RSM measurements. A non-polar overgrowth approach has also been established for the growth of non-polar GaN, leading to an impressive improvement in the crystalline quality. Meanwhile, optical investigation on c-plane InGaN/GaN MQW nanorod structures has been performed, demonstrating an significantly enhanced photoluminescence emission. It has been concluded that the enhancement is due to the reduction on quantum confined Stark effect caused by strain relaxation in the MQW structure.
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Sutherland, Danny. "Optical characterisation of non-polar InGaN/GaN quantum wells." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/optical-characterisation-of-nonpolar-ingangan-quantum-wells(34ce6283-262b-491e-ad3d-3e2ab95cb434).html.
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In this thesis I present research on the optical characterisation of InGaN/GaN quantum wells (QWs) grown in the non-polar the a-plane (11-20) and m-plane (1-100) orientations. The research is performed using optical techniques such as photoluminescence (PL), photoluminescence excitation (PLE), time-resolved photoluminescence (TRPL) and photoluminescence decay time studies. Additionally comparisons are drawn to structural details provided by the University of Cambridge. In the first section I investigate and compare various defect reduction techniques that are utilised in the growth of a-plane GaN on r-plane sapphire. These are included as a way of reducing the density of basal-plane stacking faults (BSFs) and threading dislocations (TDs). I will show that a comparison between the integrated emission intensity of the donor-bound exciton against that of the BSFs and the TDs can be used as a means of comparing the relative crystal quality of different samples. I will also show that techniques which employ a physical layer to block BSFs and TDs from propagating are the most effective in reducing their densities for a-plane GaN grown on r-plane sapphire. In the second section I discuss the characterisation of m-plane InGaN/GaN QWs, focusing primarily on the presence of an extended low energy emission tail. Through the use of decay time studies and TRPL I am able to show that the extended low energy emission tail originates from semi-polar QWs which form during growth. Additionally I show that over the majority of the emission band, the PL decay time possesses a single time constant that does not vary significantly with detection energy. This observation is consistent with the recombination of localised excitons in the m-plane InGaN/GaN QWs. For the final section I compare InGaN/GaN QWs grown on the a-plane and the m-plane for the purpose of understanding why m-plane samples typically exhibit superior optical properties. In this section I identify an additional emission band that exists on the high energy side of the QW emission and is comparably stronger in the a-plane samples. This emission band is responsible for the difference in the PL decay times observed between each non-polar growth orientation, as well for as the reduction in the degree of linear polarisation measured for a-plane QW samples.
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Xing, Kun. "Fabrication and overgrowth of semi-polar and non-polar GaN on sapphire for advanced III-nitride optoelectronics." Thesis, University of Sheffield, 2015. http://etheses.whiterose.ac.uk/9306/.
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Fabrication of nano-rod and micro-rod array templates and then overgrowth of semi-polar (11-22) and non-polar (11-20) GaN on the templates on sapphire have been performed. Two simple but cost-effective fabrication techniques based on self-organized nano-masks and ultraviolet (UV) photolithography approaches have been developed, respectively. Optimization in the fabrication of non-/semi-polar nano-rod structures and semi-polar micro-rod structures has been systematically performed. The GaN nano-rod and micro-rod arrays with high reproducibility and good uniformity across two inch wafers have been achieved. Metal organic chemical vapour deposition (MOCVD) has been employed to conduct GaN overgrowth on the semi-polar or non-polar GaN nano-rod array templates which are fabricated based on standard semi-polar or non-polar GaN on r-plane (for non-polar) or m-plane (for semi-polar) sapphire prepared using MOCVD. Great improvements in crystal quality for both semi-polar and non-polar GaN have been achieved, which have been confirmed by both x-ray and transmission electron microscopy (TEM) measurements. It has been found that the diameter of nano-rods plays a significant role in reducing dislocation density. With increasing diameter of nano-rods, the dislocation density of the overgrown GaN is reduced. By using the self-organized masks, a quick coalescence with a less than 1 µm thick layer has been achieved, which is much less than those using any conventional overgrowth techniques (typically 10-20 µm). An approach to the fabrication of semi-polar micro-rod GaN array structures has been developed, which is based on the combination of mask design and UV photolithography techniques. A systematic study on the overgrowth of semi-polar GaN on the semi-polar micro-rod GaN array structures have been performed as a function of the diameter of the micro-rods. A further reduction in the dislocation densities and especially basal stacking faults has been achieved compared with that using self-organized nano-mask approach. The mechanism for defect reduction in the GaN overgrown on nano-rod/micro-rod templates has been investigated by detailed TEM studies. The dislocations are either terminated by the SiO2 masks or the residue voids formed due to the large GaN lateral growth rate. The propagation of basal stacking fault can be blocked during the coalescence initiated from the sidewall of the adjacent nano-rods or micro-rods. InGaN/GaN multiple quantum wells (MQWs) have been grown on the semi-polar and non-polar overgrown GaN, respectively. The temperature dependent photoluminescence (PL) measurements demonstrate a significant enhancement in the internal quantum efficiency of InGaN/GaN MQWs grown on the overgrown GaN compared with that grown on as-grown c-plane, non-polar, and semi-polar GaN, respectively, as a result of the huge improvement in crystal quality and elimination or mitigation of the quantum confined Stark effect, which has been confirmed by excitation power dependent PL measurements. InGaN/GaN MQWs with a significant enhancement in indium incorporation have been achieved, demonstrating a major advantage of utilisation of semi-polar GaN for the growth of long wavelength emitters. So far, high optical performance with an emission wavelength of up to 590 nm has been demonstrated.
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Pahlevanzadeh, Hassan. "Solubility of the toxic gases, hydrogen sulfide and sulfur dioxide in some polar and non-polar solvents." Thesis, University of Ottawa (Canada), 1986. http://hdl.handle.net/10393/5243.
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Waltereit, Patrick. "(Al, Ga, In)N heterostructures grown along polar and non-polar directions by plasma-assisted molecular beam epitaxy." Doctoral thesis, [S.l.] : [s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=963284975.
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Hao, Rui. "Structural and optical characterisations of defects in non-polar and semi-polar GaN epilayers and InGaN/GaN MQWs." Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610548.
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Harper, John. "Electrochemical investigations in supercritical fluids and other non-polar media." Thesis, University of Leicester, 1998. http://hdl.handle.net/2381/30020.
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This thesis describes the use of novel electrolytes in media of extremely low relative permittivity. Double layer capacitance, conductivity and voltammetric experiments are presented and attempts are made to elucidate the ionic entities in solution and at the electrode / solution interface. Charge is found to be predominantly carried by triple ions and these have a surprisingly appreciable influence on the double layer structure.;Voltammetric responses are presented in dichloroethane (DCE), anisole (Anis) and cyclohexane (cHex) and it is shown that the reversibility of a process is affected by the length of the tetraalkylammonium chain of the electrolyte. Reversible responses are only observed at very slow sweep rates, and this is a result of the slow electrode desorption kinetics of the electrolyte ions. This has profound consequences for electrochemical studies made in non-aqueous media using quaternary ammonium electrolytes.;Finally, bulk electrolysis experiments are performed in scCO2/water mixtures. It is shown that formate and hydrogen are primarily formed on a platinum surface, whereas oxalate and hydrogen are the major products on lead. This is ascribed to a change in reaction pathway compared to such studies in aqueous media. Supercritical fluids are shown to have significant advantages over liquid solvents for the electrochemical reduction of CO2.
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Greenberg, Marc Samuel. "Defining Benthic Organism Exposure: Bioavailability and Effects of Non-Polar Organics." Wright State University / OhioLINK, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=wright1074096654.
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Royal, Damian Derek. "Dielectric constants of simple gases determined using microwave cavity resonators." Thesis, University College London (University of London), 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.313301.
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Truscott, Christopher Leslie. "Supramolecular chemistry at the polymer-oil interface." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/277920.
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The movement away from metals towards polymers for automobile bearing coatings opens a new area for the possible modification of these coatings. This project, done in collaboration with Castrol, was to understand adsorption of small molecules at the surface of these polymers and work towards engineering host-guest interactions at the surface to provide binding of specific molecules. Initially, the commercial polyamide-imide was characterised via Nuclear Magnetic Resonance (NMR), Infrared (IR) and Ultra-Violet/Visible (UV-Vis) spectroscopy to understand the nature of the functional groups and structures present. This revealed that the imidisation reaction was incomplete so the functionality within the polymer could change and thus alter how molecules interact with it. This reaction was then investigated via IR and NMR spectroscopy and it was shown that the degree of imidisation varied with temperature. Then the characterised polyamide-imide was used to study the adsorption of alkylphenols, a class of molecules that have structures and functionality like common additives used in engine oils. Additionally, the adsorption of water was studied as it is a common contaminant. These two systems were studied via solution depletion isotherms and neutron reflectivity measurements. The isotherms confirmed the adsorption of the molecules whilst neutron reflection was used to characterise the layers. For alkylphenol, a rather sparsely packed layer of the molecules and solvent existed at the surface with their alkyl tails extending into the solvent. For water; the molecules diffuse into the polyamide-imide. It can be partially removed by washing the surface with dry dodecane; however, some water remains in the polymer layer. A viologen-cucurbit[8]uril binding site was chosen as the supramolecular surface interaction. The binding unit was incorporated into the polyamide-imide. The synthesis of the binding site polymer was achieved in two stages; the reproduction of the commercial polymer and the synthesis of a polymer containing 100% viologen with and without threaded cucurbit[8]uril. Whilst the synthesis appeared successful, neutron reflectivity measurements showed that, when in contact with a solution containing a second guest, no adsorption was seen on the polymer containing cucurbit[8]uril. In order to study the supramolecular interaction in non-polar solvent, a series of rotaxanes were synthesised with viologen-cucurbit[8]uril cores and bulky stopper groups to prevent unthreading of the cucurbituril as well as enhancing the solubility of the system. The two components were linked via an amidisation reaction between an acid chloride and an amine. Due to the low solubility of the products confirmation of synthesis was only possible in one case. As well as using a viologen-cucurbit[8]uril binding site, binding in cucurbiturils via halogen bonding was investigated as common halogen bonding species show good solubility in non-polar solvents. Initially co-crystals of 2,5-diiodo-1,3,4,6-tetrafluorobenzene with tertiary amides were studied. With N,N-dimethylformamide, a 1:2 co-crystal was seen but the structure with N-methyl-2-pyrrolidone had a stoichiometry of 1:1. In both structures the oxygen of the amide is involved in a halogen bonding; however, for N-methyl-2-pyrrolidone it is bifurcated leading to the formation of chains. A 50-50 mixture of pyridine and formic acid was found to solubilize both halogen bond donors and cucurbit[n]uril. Over the course of these experiments the structure of the co-crystals of two halogen bond donors, 2,5-diiodo-1,3,4,6-tetrafluorobenzene and 2,4,6-triiodo-1,3,5-trifluorobenzene, with pyridine were determined. Crystals of the cucurbituril-adducts weren’t of sufficient quality to determine the structure. The presence of binding solution was confirmed by 1H and 19F NMR experiments on the methyliodide-cucurbit[6]uril and Trans-diiodooctrafluoroazobenzene-cucurbit[8]uril systems.
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Mohammed, Ali Mohammed Jassim. "Optical characterisation of non polar nanostructures quantum wells ZnO/(Zn,Mg) O." Thesis, Montpellier, 2018. http://www.theses.fr/2018MONTS096/document.
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L’oxyde de zinc est un matériau prometteur pour la réalisation de composants optoélectroniques dans la gamme des émetteurs UV. Pour cela il faut développer des hétéro-structures tel que des puits quantiques ZnO/(Zn, Mg)O afin de mieux contrôler les propriétés d’émissions. Ce travail porte sur la caractérisation de telles structures crûes sur le plan A, surface non polaire, de ZnO massif. A partir de mesures de spectroscopie optiques (réflectivité, photoluminescence en excitation continue et photoluminescence résolue en temps) nous avons déterminé les différents phénomènes physiques mis en jeux lors de la recombinaison radiative des porteurs dans ces puits quantiques. Dans un premier temps, nous avons étudié en détail l’émission des photons par les barrières de (Zn, Mg)O. Grace à l’étude en température nous avons montré que l’émission optique de la barrière correspond à la recombinaison de paires électron trou en interactions (excitons) qui sont à basses températures localisées dans des fluctuations de potentiel. Sous l’effet de la température ils se délocalisent et se recombinent comme des exciton libres. L’étude détaillée des déclins temporels de photoluminescence nous à permis de démontrer que nous avions affaire à deux états excitoniques différents qui présentent des dynamiques de recombinaisons différentes. Un modèle est proposé pour rendre compte des différentes observations. La partie principale de ce travail porte sur le comportement des excitons dans le puits quantique. Le résultat majeur de cette étude est la démonstration expérimentale que dans ce cas des complexes excitoniques, ici des trions chargé négativement (exciton en interaction avec un électron libre), se forment à basse température et sont responsable de la luminescence observée. De plus, en variant la densité d’excitation nous avons montré que se former également des bi-excitons (pseudo particule formée de deux exciton en interactions). Le comportement en température de la photoluminescence obtenue dans différente conditions d’excitation à permis de démontrer que sous l’effet de l’énergie thermique les complexes excitoniques se dissociés pour créer des excitons libres. Des mesures en fonction de la polarisation de la lumière émise et de la température ont permis également d’étudier l’état C de l’exciton dans le puits. Les dynamiques de recombinaison des différents complexes excitoniques sont examinées en fonction de la températureThe zinc oxide is a promising material for the realization of optoelectronic devices in the blue-UV range. For this, it is necessary to develop hetero-structures such as ZnO / (Zn, Mg) O quantum wells in order to have better control of the properties of emissions. This work concerns the characterization of such structures grown on the A-plane (non-polar surface) of bulk ZnO. From optical spectroscopies measurements (reflectivity, continuous wave and time-resolved photoluminescence) we determined the various physical phenomena involve during the radiative recombination of the carriers in these quantum wells. At first, we studied in detail the emission of photons by the barriers of (Zn, Mg) O. Thanks to the study in temperature we showed that the optical emission of the barrier corresponds to the recombination of electron hole pairs in interactions (excitons), which are at low temperatures localized in the fluctuations of the potential. Under the influence of the temperature they delocalize and recombine as free exciton. From the detailed study of the temporal decays of photoluminescence we can demonstrate that we deal with two different excitonic states, which present different dynamics of recombination. A model is proposed that explain the various observations. The main part of this work concerns the behavior of the excitons in the quantum well. The major result is the experimental demonstration that excitonics complexes are formed at low temperature, negatively charged trion (exciton in interaction with a free electron), in this system and they are responsible for the observed luminescence. Furthermore, by varying the density of excitation we showed that biexcitons are also form (pseudo-particles formed by two excitons in interactions). The behavior in temperature of the photoluminescence obtained in different conditions of excitation demonstrates that under the influence of the thermal energy the exitonic complexes are broken to create free excitons. Measures according to the polarization of the emitted light and the temperature also allowed studying the C state of the exciton in the quantum well. The dynamics of recombination of the various excitonics complexes are examined according to the temperature
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Kister, Thomas [Verfasser]. "The stability and assembly of sterically stabilized non-polar nanoparticles / Thomas Kister." Saarbrücken : Saarländische Universitäts- und Landesbibliothek, 2021. http://d-nb.info/1238595510/34.
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Harper, Neil. "Studies on the ionisation state of subtilisin Carlsberg in non-polar organic solvents." Thesis, University of Strathclyde, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366691.
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Sharma, Shachi Dayal Gurumayum. "Investigation of the surface interactions of polymer and surfactants in non-polar media." Thesis, University of Bristol, 2002. http://hdl.handle.net/1983/05b71826-61f9-4538-83c1-441df72cb452.
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Oishi, Yohei. "Dynamics and structure of polybutadienyl lithium living anionic chains aggregated in non-polar solvent." 京都大学 (Kyoto University), 2007. http://hdl.handle.net/2433/136259.
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Moldawer, Adam Lyle. "Growth of polar and non-polar nitride semiconductor quasi-substrates by hydride vapor phase epitaxy for the development of optoelectronic devices by molecular beam epitaxy." Thesis, Boston University, 2013. https://hdl.handle.net/2144/11151.
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Thesis (Ph.D.)--Boston UniversityThe family of nitride semiconductors has had a profound influence on the development of optoelectronics for a large variety of applications. However, as of yet there are no native substrates commercially available that are grown by liquid phase methods as with Si and GaAs. As a result, the majority of electronic and optoelectronic devices are grown heteroepitaxially on sapphire and SiC. This PhD research addresses both the development of polar and nonpolar GaN and AIN templates by Hydride Vapor Phase Epitaxy (HVPE) on sapphire and SiC substrates, as well as the growth and characterization of optoelectronic devices on these templates by molecular beam epitaxy (MBE). Polar and non-polar GaN templates have been grown in a vertical HVPE reactor on the C- and R-planes of sapphire respectively. The growth conditions have been optimized to allow the formation for thick (50µm) GaN templates without cracks. These templates were characterized structurally by studying their surface morphologies by SEM and AFM, and their structure through XRD and TEM. The polar C-plane GaN templates were found to be atomically smooth. However, the surface morphology of the non-polar GaN films grown on the R-plane of sapphire were found to have a facetted surface morphology, with the facets intersecting at 120° angles. This surface morphology reflects an equilibrium growth, since the A-plane of GaN grows faster than the M-planes of GaN due to the lower atomic density of the plane. For the development of deep-UV optoelectronics, it is required to grow AIGaN quantum wells on AIN templates. However, since AIN is a high melting point material, such templates have to be grown at higher temperatures, close to half the melting point of the material (1500 °C). As these temperatures cannot be easily obtained by traditional furnace heating, an HVPE reactor has been designed to heat the substrate inductively to these temperatures. This apparatus has been used to grow high-quality, transparent AIN films with a screw dislocation density of 10^6 cm^-2 on sapphire repeatedly. On such templates, both lnGaN- and AIGaN-based quantum wells (QWs) and quantum dots (QDs) were formed by MBE and were characterized. lnGaN/GaN and AIGaN/AIN QWs were grown on the non-polar GaN templates and found to emit at near green and deep UV respectively with internal quantum efficiency (IQE) close to 90%. The lnGaN GaN QWs and QDs have been investigated to understand the influence of plasmonic nanoparticles on the efficiency of corresponding green LEOS.
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Wallqvist, Viveca. "Interactions between non-polar surfaces in water: Fokus on talc, pitch and surface roughness effects." Doctoral thesis, KTH, Ytkemi, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-10283.
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The aim of this thesis work was to gain understanding of the interactions between talc mineral and surfaces, liquids and chemicals relevant for industrial applications, such as pulp and paper. Talc is used in the pulp and paper industry as a filler pigment, in control of pitch (lipophilic extractives) deposits and as a coating pigment. A deeper understanding of talc interactions will be beneficial in optimizing its use. Long-range attractive interactions between talc and hydrophobic model probes, as well as pitch probes, have been measured using the atomic force microscope (AFM) colloidal probe method. Two procedures for preparation of pitch colloidal probes were developed to allow these studies. Model hydrophobic, nanorough surfaces with surface energy characteristics similar to talc have also been prepared and their interactions with hydrophobic model probes compared to interactions between hydrophobic model probes and talc. It is demonstrated that talc mineral interacts with model hydrophobic particles, as well as with pitch, by long-range attractive forces, considerably stronger than the expected van der Waals force. The possible origin of the measured interaction forces is discussed, and the conclusion is that the main cause is an attractive capillary force due to formation of a gas/vapor capillary between the surfaces. Force measurements using model hydrophobic, nanorough surfaces show that a large-scale waviness does not significantly influence the range and magnitude of the capillary attraction, but large local variations in these quantities are found. It is demonstrated that a large variation in adhesion force corresponds to a small variation in local contact angle of the capillaries at the surfaces. The nature of the surface topographical features influences the capillary attraction by affecting the local contact angle and by pinning of the three-phase contact line. The effect is clearly dependent on the size of the surface features and whether they exist in the form of crevices or as extending ridges. Entrapment of air also affects the imbibition of water in pressed talc tablets. The effects of wetting and dispersion agents on the interactions between talc and hydrophobic probes have also been investigated. It is demonstrated that a common dispersing agent used for talc, poly(acrylic acid), does not affect the capillary attraction between talc and non-polar probes. In fact, the results strongly suggest that poly(acrylic acid) does not adsorb on the basal plane of talc. From this finding it is inferred that the stabilizing effect of this additive most likely is due to adsorption to the edges of talc. In contrast, a wetting agent (the non-ionic triblock copolymer Pluronic PE6400) removes the long-range capillary attraction. It is suggested that such an ability to replace air at the talc surface is of great importance for an efficient wetting agent. The Hamaker constant for talc has also been estimated by using optical data obtained from spectroscopic ellipsometry. It is demonstrated that a nanocrystalline talc mineral, cut in different directions displays very small differences in Hamaker constant between the different crystallographic orientations, whereas a microcrystalline sample displays a significantly higher value. The estimated Hamaker constants are discussed for different material combinations of relevance for the pulp- and paper industry, such as cellulose and calcium carbonate.Målet med detta avhandlingsarbete var att öka förståelsen för interaktioner mellan talkmineral och ytor, vätskor och kemikalier relevanta för industriella applikationer, såsom papper och massa. Talk används i pappers- och massaindustrin som fyllmedel, för kontroll av hartsrika (lipofila extraktivämnen) avsättningar och som bestrykningspigment. En djupare förståelse för talkinteraktioner kommer att vara användbart för att optimera dess användning. Långväga attraktiva interaktioner mellan talk och hydrofoba modellpartiklar, såväl som mellan talk och hartspartiklar, har uppmätts med hjälp av atomkraftsmikroskopi (AFM) genom att fästa kolloidala partiklar på kraftsensorn. Två metoder för att framställa partiklar gjorda av harts har utvecklats för att möjliggöra dessa studier. Hydrofoba, nanostrukturerade modellytor med ytenergier liknande de för talk har också tillverkats och deras växelverkan med hydrofoba modellpartiklar har jämförts med dem mellan talk och hydrofoba modellpartiklar. Studierna visar att talkmineral växelverkar med hydrofoba modellpartiklar, såväl som med harts, genom långväga attraktiva krafter som är betydligt starkare än den förväntade van der Waals kraften. Möjliga orsaker till de uppmätta växelverkanskrafterna diskuteras och slutsatsen blir att huvudorsaken är en attraktiv kapillärkraft som uppkommer genom att en gas-/ångkapillär bildas mellan ytorna. Kraftmätningar gjorda med hydrofoba nanostrukturerade modellytor visar att en storskalig vågighet inte nämnvärt påverkar storleken av kapillärattraktionen, men stora lokala variationer existerar. Det demonstreras att en stor variation i adhesionskraft motsvaras av en liten variation i lokal kontaktvinkel för kapillärerna på ytorna. Ytornas topografi påverkar kapillärattraktionen genom att påverka den lokala kontaktvinkeln samt genom att trefaskontaktlinjen inte kan röra sig fritt över ytan. Effekten är tydligt beroende av huruvida ytojämnheterna existerar i form av nedsänkningar eller upphöjningar. Instängd luft påverkar också pressade talktabletters uppsugningsförmåga av vatten. Vätnings- och dispergeringsmedels inverkan på växelverkan mellan talk och hydrofoba partiklar har undersökts. Resultaten visar att ett vanligt dispergeringsmedel för talk, polyakrylsyra, inte påverkar kapillärattraktionen. I själva verket tyder data på att polyakrylsyra inte adsorberas på talks basalplan. Utifrån dessa resultat dras slutsatsen att polyakrylsyra stabiliserar talkdispersioner genom att adsorbera på talkkanterna. Ett vanligt vätmedel (nonjonisk triblock sampolymer Pluronic PE6400) tar å andra sidan bort långväga kapillärattraktion. Detta antyder att egenskapen att ersätta luft på talkytan är av stor betydelse för effektiva vätmedel. Hamakerkonstanten för talk har uppskattats genom att utnyttja optiska data från ellipsometrimätningar. Det demonstreras att ett nanokristallint talkmineral kapat i olika riktningar uppvisar mycket små skillnader i Hamakerkonstant mellan de olika kristallografiska orienteringarna, medan ett mikrokristallint prov uppvisar ett betydligt högre värde. De beräknade Hamakerkonstanterna diskuteras för olika materialkombinationer relevanta för pappersindustrin, såsom cellulosa och kalciumkarbonat.
QC 20100813
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Prevot, Michelle Elizabeth. "Introduction of a thermo-sensitive non-polar species into polyelectrolyte multilayer capsules for drug delivery." Phd thesis, [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=980963354.
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Jones, Christopher. "The role of water in the aggregation behaviour of surface active molecules in non-polar solvents." Thesis, University of Surrey, 2011. http://epubs.surrey.ac.uk/843130/.
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Asphaltenes represent some of the largest and most polar molecules found in crude oils and are known to be surface active. Whilst one of the least valuable fractions of a crude oil, asphaltenes have never-the-less received a great deal of scientific attention due to the risks their behaviour poses to oil recovery, transportation and processing. Subtle changes in the chemistry of crude oils or physical conditions can cause changes in the aggregation state of asphaltenes, which may precipitate out of solution blocking pores in reservoir rocks, altering surface wettability or fouling pipelines and refinery equipment. The complex and polydispersed nature of asphaltenes and their propensity to aggregate in solution makes them very difficult to characterise and despite many studies a definitive picture of their chemistry, molecular weight and aggregation behaviour has not been found. The aggregation state, geometry and molecular weight of petroleum asphaltenes are investigated using a Langmuir trough in Chapter 2. A novel mathematical model based upon the van der Waals modified equation of state was used to predict aggregation numbers and limiting areas of asphaltene aggregates at the air water interface. Non-ionic surfactants are widely used in many industries including many stages of oil recovery and production. The solubility and aggregation behaviour of a commercial surfactant in non-polar solvents is investigated in Chapter 3. Anomalous solubility behaviour at low surfactant mole fractions is investigated and the underlying mechanisms are discussed. The importance of water to the aggregation behaviour of non-ionic surfactants is a recurring theme in the scientific literature. The interaction between a commercial non-ionic surfactant in non-polar solution and water is reported in Chapter 4. A mechanism is proposed to explain aggregation states which vary significantly with water content and its limitations are discussed.
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Rosales, Daniel. "Etude des propriétés optiques de nanostructures quantiques semi-polaires et non-polaires à base de nitrure de gallium (GaN)." Thesis, Montpellier, 2015. http://www.theses.fr/2015MONTS180/document.
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Nous étudions les propriétés optiques de nanostructures (Al,Ga)N/GaN crûes selon diverses orientations cristallographiques. Les orientations concernées sont : le plan non-polaire (1-100) ou plan m ; le plan semi-polaire (1-101) ou plan s ; et le plan semi-polaire (11-22). Dans un premier temps, nous nous consacrons à l'étude de l'anisotropie de la réponse optique de puits quantiques crûs selon les plans m et s. Dans un deuxième temps, nous évaluons les effets de la température sur les propriétés optiques de ces puits quantiques en utilisant la technique de photoluminescence résolue en temps qui permet d'obtenir des informations concernant les phénomènes radiatifs et non-radiatifs. S'agissant des durées de vie radiatives, nous avons mis en évidence la contribution de deux régimes de recombinaison: celui des excitons localisés, lequel est caractérisé par une durée de vie constante; et celui des excitons libres dont la durée de vie croit linéairement avec la température. Pour tous les échantillons que nous avons étudié, le régime d'excitons localisés domine à basse température alors que le régime d'excitons libres domine à haute température. Nous avons ainsi caractérisé la qualité des interfaces des puits quantiques (Al,Ga)N/GaN à partir de la détermination d'un modèle de la densité d'états de localisation. Nous trouvons qu'elle est, dans nos échantillons, encadrée par des valeurs comprises entre 10^11 - 10^12 cm-2. Notre étude montre que les puits orientés (11 22) présente la plus faible densité, et que les puits orientés selon le plan s sont les moins affectés par les phénomènes non-radiatifs. Dans un troisième temps, nous nous sommes intéressés à la caractérisation de nanostructures crûes selon le plan (11-22) pour diverses conditions de croissance. En faisant varier celles-ci, il est possible d'obtenir des boites quantiques, des fils quantiques, ou des puits quantiques. L'étude de la dynamique de recombinaison des excitons dans ces nanostructures (11-22) montre une dépendance en température de la durées de vie radiative en fonction du degré de confinement : constante pour les boîtes quantiques; proportionnelle à racine de T pour les fils ; linéaire pour les puits. Cette étude démontre la richesse de possibilités de nanostructures crûes sur des orientations non-traditionnelles elle mets en perspective de nouvelles études de croissance cristalline de nano-objets pour des applications inédites en optoélectroniquesWe study the optical properties of (Al,Ga)N/GaN nanostructures grown along several crystallographic orientations. The involved orientations are: the non-polar (1-100) plane or m-plane; the semi-polar (1-101) or s-plane; and the semi-polar (11-22) plane. First, we focus on the study of the anisotropy of the optical response of quantum wells grown in m- and s-planes. Second, we evaluate the effects of the temperature on optical properties of these quantum wells by extensive utilization of the time-resolved photoluminescence technique. It allows to obtain information regarding the evolution of radiative and non-radiative phenomena with temperature. Concerning radiative decay times, we have discriminated the contributions of two recombination regimes: the recombinations of localized excitons characterized by a constant decay time; and the recombinations of free excitons whose decay time increases linearly with the temperature. For all samples studied here, the regime of recombination of localized excitons dominates at low temperature and the regime of recombination of free excitons dominates at high temperature. In addition, we characterized the quality of (Al,Ga)N/GaN interfaces by the determination of the density of localization states. The values are ranging between 10^11 cm-2 and 10^12 cm-2 in our samples. This study demonstrates that (11-22)-oriented quantum wells exhibit the lowest density, and we find that the optical properties of s-plane oriented wells are the less impacted by the non-radiative phenomena. Third, we concentrated on the characterization of nanostructures grown along (11-22) plane direction under very different growth conditions. By modifying them, it is possible to obtain either quantum dots, or quantum wires or quantum wells. The study of the exciton recombination dynamics in these (11-22)-oriented nanostructures reveals a temperature dependence of radiative decay times correlated with the dimensions of the confining potentials: it is constant for the quantum dots; proportional to square root of T for quantum wires; and linear for quantum wells. This study demonstrates the potentialities of the nanostructures grown on non-traditional orientations for optoelectronic applications
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Nishat, Md Rezaul Karim. "DESIGN OF NANOSTRUCTURED ENTANGLED PHOTON PAIR GENERATOR FOR QKD APPLICATIONS." OpenSIUC, 2018. https://opensiuc.lib.siu.edu/dissertations/1580.
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Finite structure splitting (FSS) is a bottleneck for quantum dot (QD) based solid state entangled photon pair generator (EPPG) for Quantum Key Distribution (QKD) application. In QD, entangle photon pairs are generated through a cascaded emission process—biexciton to exciton to ground state. The FSS of the excitonic state destroys the entanglement of the photon pairs, hence needs to be eliminated. FSS can be tuned by engineering the crystal growth direction, varying dot shape or size, changing the material composition and/or applying external strain. Numerical investigation of FSS and designing of realistically-sized QD based EPPG demands multiscale-multiphysics many-body simulation efforts. To this end, in this work, we report the coupling of full configuration integration (FCI) method with the atomistic empirical tight-binding (TB) models (10-band sp3s* and 20-band sp3d5s*) to calculate the excitonic energetics and FSS in recently reported multimillion-atom III-V dot-in-nanowire structures. The core of the computational framework comprises two parts: i) NEMO3D, which, using the TB models, can compute single-electron energetics of multimillion-atom structures, and ii) An FCI kernel, which computes the many-particle energetics and wavefunctions using the single-electron outputs as derived from NEMO3D. NEMO3D is a broad platform that handles geometry construction, calculation of strain distributions and built-in potential fields, solving the Schrodinger’s equation and computing optical matrix elements. Three output files from NEMO3D are of particular importance for the FCI toolkit: i) Single-electron energy values, ii) Eigen functions, and iii) Relaxed atom positions of the device. FCI calculates the Coulomb and Exchange matrix elements associated with multi-particles and forms the many-body Hamiltonian. The excitonic states (electron-hole pair) are calculated by solving the many-body Hamiltonian and the value of FSS, if exists, is determined. Recently, nitride-based nanostructured devices have been found to be a promising candidate for single and entangled multi-photon emitter applications. The principal goal of this dissertation is to facilitate the numerical design of InGaN/GaN based dot-in-nanowire EPPG units. To this end, a number of kernels in NEMO3D and FCI packages were augmented. The geometry constructor in NEMO3D was extended for two non-polar planes of wurtzite crystal: m-plane and a-plane. It is found that these two non-polar planes, with much smaller built-in piezoelectric fields, exhibit improved optical transition probabilities than the polar c-plane counterpart. As test cases, light-emitters in dot-in-wire and multiple quantum well (MQW) configurations were simulated and compared in all three (c-plane, m-plane, and a-plane) growth directions. TCAD toolkits are used to simulate the terminal optical characteristics such as internal quantum efficiency (IQE) and spontaneous emission rate. Hexagonal-base truncated-pyramid shaped QD was also added to the NEMO3D geometry constructor as pyramid shaped dots offer directionality and better extraction efficiency of emitted photons, which is important for single or entangled photon generators. The FCI simulator was modified for calculating the excitonic states that involve an electron-hole pair. As for EPPG design, four device structures are considered: i) Disk-in-nanowire on the polar c-plane, ii) pyramid shaped dot-in-nanowire on polar c-plane, iii) Disk-in-nanowire on non-polar m-plane, and iv) Disk-in-nanowire on non-polar a-plane. Simulations are done for different disk thicknesses, material compositions, quantum dot shapes and crystal directions. Results and in-depth analysis are presented on the effects of these design parameters on many-body energetics e.g. binding energy, excitonic bandgaps and FSS. The derivation of excitonic transition probability from single-electron momentum matrix is discussed in detail. Finally, an EPPG design is proposed employing the entangled polarization profiles from two excitonic emissions.
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Lowe, Douglas. "Design and implementation of a multi-component, non-equilibrium model for the study of polar stratospheric clouds." Thesis, Lancaster University, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.421629.
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Miller, John Francis. "The determination of very small electrophoretic mobilities of dispersions in non-polar media using phase analysis light scattering." Thesis, University of Bristol, 1990. http://hdl.handle.net/1983/45ef1314-ee97-4667-b179-a073b73d568d.
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An apparatus is described that can determine electrophoretic mobilities of polar and non-polar colloidal dispersions down to -12 2 10 msV -1 -1 with typical resolutions of 0.5 to 5%, depending on the nature of the dispersion being studied. The diffusion coefficient and settling/convection velocity of the sample may be determined simultaneously in real time with the electrophoretic mobility. The technique, phase analysis light scattering (PALSY, is based upon classical laser-Doppler electrophoresis, but employs signal processing of the time domain phase information within the scattered light signal, rather than analysis of its frequency spectrum. This allows much smaller electric field strengths to be employed, thereby alleviating the usual heating problems associated with electrophoretic studies of non-polar dispersions. PALS measurements of typical aqueous latex dispersions with large mobilities and non-polar dispersions with very small mobilities (down to 5x 10_12 m2 s-1 V-1) are presented to illustrate the versatility of the technique.
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Ni, Xianfeng. "Growth and characterization of non-polar GaN materials and investigation of efficiency droop in InGaN light emitting diodes." VCU Scholars Compass, 2010. http://scholarscompass.vcu.edu/etd/2235.
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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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Wu, Mo. "AlGaN/GaN Dual Channel HFETs and Realization of GaN Devices on different substrates." VCU Scholars Compass, 2012. http://scholarscompass.vcu.edu/etd/403.
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GaN-based HFETs demonstrate ubiquitous high power and high frequency performance and attract tremendous research efforts. Even though significant advances have been achieved, there still exist some critical issues needed to be investigated and solved. In particular, high defect densities due to inhomogeneous growth and operation under high power conditions bring many unique problems which are not so critical in the conventional Si and GaAs materials systems. In order to reduce the defect density and heat dissipation of GaN-based HFETs, research work on the realization of GaN-based HFETs on bulk GaN substrate has been carried out and the key problems have been identified and solved. Hot phonon scattering is the bottleneck which limits the enhancement of electron velocity in the GaN 2DEG channel. It is found that the plasmon-phonon coupling is the mechanism for converting of hot phonons into high group velocity acoustic phonons. In order to push more electrons into the GaN 2DEG channel in the plasmon-phonon coupling regime and to further reduce the hot phonon lifetime, a novel AlGaN/GaN dual channel HFET structure has been proposed. The growth, fabrication and characterization of such a AlGaN/GaN dual channel HFET structure has been carried out. Conventionally GaN-based light emitting diodes and laser diodes are grown and fabricated using the c-plane III-nitride expitaxy layers. In c-plane III-nitride epi-layers, the polarization-induced electric field introduces spatial separation of electron and hole wave functions in quantum wells (QW)s used LEDs and laser diodes LDs and degrades quantum efficiency. As well, blueshift in the emission wavelength becomes inevitable with increasing injection current unless very thin QWs are employed. The use of nonpolar orientations, namely, m-plane or a-plane GaN, would solve this problem. So far, m-plane GaN has been obtained on LiAlO2 (100), m-plane SiC substrates, and m-plane bulk GaN, which all have limited availability and/or high cost. Silicon substrates are very attractive for the growth of GaN due to their high quality, good thermal conductivity, low cost, availability in large size, and ease with which they can be selectively removed before packaging for better light extraction and heat transfer when needed To realize the low cost and improve the internal quantum efficiency of GaN based light emitting diodes, the process for m-plane GaN growth on Si (112) substrates has been studied and optimized. The continuous m-plane GaN film is successfully grown on Si (112) substrates.
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Hillbrick, Gordon Colin, and kimg@deakin edu au. "THE LIPID COMPOSITION OF CASHMERE GOAT FIBRES." Deakin University, 1994. http://tux.lib.deakin.edu.au./adt-VDU/public/adt-VDU20031205.162817.
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This study examined the differences in the chemical composition, particularly fatty acids, of the lipid extracted from the fibre of bucks, does and castrated goats. The study provides a more detailed understanding of the chemical composition of buck fibre lipid and how it varies throughout the year, and also details the effect of body region and nutrition on the production and chemical composition of lipid from buck fibre.
Lipid was extracted with either petroleum ether (non-polar) or chloroform/methanol azeotrope (polar) and analysed by gas chromatography and gas chromatography-mass spectrometry. The more polar solvent system extracted larger amounts of lipid and more of each individual fatty acid. The following buck specific ethyl branched fatty acids were identified: 2-ethylhexanoic, 4-ethylhexanoic, 2-ethyloctanoic, 4-ethyloctanoic, 6-ethyloctanoic, 2-ethyldecanoic, 4-ethyldecanoic, 2-ethyldodecanoic, 6-ethyldodecanoic, 4-ethyldodecanoic, 2-ethyltetradecanoic, 6-ethyltetradecanoic, 4-ethyltetradecanoic, 2-ethylhexadecanoic and 4-ethyloctadecanoic acids. Of these buck specific fatty acids only 4-ethylhexanoic (T), 4-ethyloctanoic, 4-ethyldecanoic, 4-ethyldodecanoic, 6-ethyldodecanoic (T), 4-ethyltetradecanoic, 2-ethylhexadecanoic (T) and 4-ethylhexadecanoic acids have been previously identified or tentatively identified (T) in buck fibre extracts. This shows that the chemical composition of buck fibre lipid is more complex than previously reported, and that it may be more difficult than previously thought to artificially duplicate the odour of the buck.
Buck fibre samples had lower average
concentrations of 2-methylpropanoic, 2-methylbutanoic, iso-pentadecanoic, anteiso-pentadecanoic, iso-hexadecanoic, anteiso-heptadecanoic, iso-octadecanoic and anteiso-nonadecanoic acids as compared with fibre samples from does, spayed does, or wethers that were castrated at one month of age. The reduced concentrations of these fatty acids in buck fibre extracts were likely to be due to the synthesis of ethyl branched derivatives of iso and anteiso fatty acids. Buck fibre samples had higher concentrations of benzoic acid as compared with fibre samples from does, spayed does, or wethers that were castrated at one month of age. The significance of these results is that non buck specific fatty acids may also make a contribution to the odour of bucks.
When fibre samples were collected at various times throughout the year, it was found that the bucks had increased amounts of lipid and ethyl branched fatty acids in fibre samples shorn from March to September, as compared with fibre samples shorn in November and January. The increase in the amount of lipid and ethyl branched fatty acids corresponded with both the rutting period of the buck and the period when the buck odour was increased. This suggests that ethyl branched fatty acids could be pheromones.
The variation in lipid content and fatty acid composition was also examined between fibre samples collected from different body regions of the buck during April, as alterations in sebaceous gland activity around the neck during rutting have been reported. It was found that the average amount of lipid in the neck region of the bucks was not statistically higher than the average amounts in the midside and hind regions. However, the ethyl branched fatty acid concentrations were statistically higher in the fibre from around the neck as compared with the fibre from the other body regions, which is consistent with the odour of the buck being most pronounced around the head and neck region.
The lipid content and composition of fibre samples from bucks fed high and low quality diets (lucerne and pangola grass, respectively) was examined to determine the effect of nutrition on buck specific components. The high quality diet increased the amount of lipid and ethyl branched fatty acids in fibre samples collected in April from the neck, midside and hind regions, as compared with fibre samples from the corresponding body regions from bucks fed the low quality diet. Thus it may be possible for the pheromone levels of bucks to be increased by simply providing them with good nutrition.
The lipid content and ethyl branched fatty acid concentrations of fibre samples increased earlier in the year for the lucerne fed bucks as compared with the pangola grass fed bucks. The lucerne fed bucks had increased concentrations of ethyl branched fatty acids in fibre samples shorn during December to June (6 months) whereas the pangola grass fed bucks had increased concentrations of ethyl branched fatty acids in fibre samples shorn during April to August (4 months). These observations show that good nutrition can result in both the earlier production of ethyl branched fatty acids and an extended period when ethyl branched fatty acids are produced. This suggests that nutrition can be used to manipulate pheromone levels in the buck. The period when the ethyl branched fatty acids were increased corresponded with the period when the plasma luteinizing hormone (LH) and testosterone concentrations, odour and sebaceous gland volume of the bucks were increased, which supports the assumption that ethyl branched fatty acids are involved in odour production and act as pheromones.
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Huang, Pei-lun, and 黃姵綸. "Internal quantum efficiency of polar and non-polar GaN and InN." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/78s3yh.
Full textAbstract:
碩士國立中山大學
物理學系研究所
97
This thesis discusses the crystal quality and transition of electrons and holes pairs by temperature- and power- dependent Photoluminescence (PL). With the PL spectra, we apply four kinds of Internal Quantum Efficiency (IQE) formulas for c- and m- plane III-nitride and discuss the differences of the four formulas. An analysis of IQE is performed and it is found for m-plane III-nitride being larger than c-plane III-nitride. This result confirms that characteristic m-plane structure can increase its radiative recombination.
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Liao, Wei-Tsai, and 廖偉材. "Characteristics of polar and non-polar GaN-based films and light-emitting diodes." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/67875869478802547985.
Full textAbstract:
博士逢甲大學
材料科學所
95
Polar AlxGa1-xN (0≦x≦0.5) films and AlxGa1-xN/GaN hetero- structures were grown on (0001) and (11-20) sapphire substrates at elevated temperatures by alternate supply of trimethylgallium (TMG) with (or without) trimethylaluminum (TMA) in group III flow and ammonia (NH3) in group V stream. The optical characteristics of GaN films deposited on (11-20) sapphire substrates were found to be comparable to those of GaN films grown on (0001) sapphire substrates under the same growth conditions. It appears that an increment of V/III ratio allows to improve the morphological and optical properties of a GaN film deposited on the (11-20) sapphire substrate. The best quality GaN films were achieved at a V/III ratio of 10400 with a quenched yellow luminescence and an enhanced room temperature near band edge photoluminescence (PL) emission having a linewidth of ~ 120 meV. Besides GaN-related thin films, we also report a comparative study on the performance of InGaN/AlGaN multiple quantum well light-emitting diodes (LEDs) fabricated on (0001) and (11-20) sapphire substrates by atmospheric pressure metalorganic vapor phase epitaxy (APMOVPE), respectively. It was found that the LEDs grown on (11-20) sapphire substrates exhibited enhanced electroluminescence intensity, decreased double crystal x-ray diffraction linewidth, reduced etching pit density, and smaller ideality factor compared to those deposited on (0001) sapphire substrates. The improved LED characteristics are attributed to threading dislocation density decrement inside the LEDs due to the reduced mismatch between LED structure and (11-20) sapphire substrate. Non-polar (11-20)-oriented GaN films were grown on (1-102) sapphire substrates at elevated temperatures using low-temperature(LT)-AlN buffer layers by alternate supply of TMG and NH3 in an inductively heated quartz reactor operated at atmospheric pressure. The structural, morphological and optical characteristics of the non-polar GaN films were investigated using x-ray diffractometry, transmission electron microscopy (TEM), field emission scanning electron microscopy, and PL spectroscopy. It was found that the non-polar GaN films were mono-crystalline in nature and the surface morphologies of the films were greatly improved by introducing LT-AlN buffer layers having certain thicknesses. Various types of threading dislocations (TDs) were identified by TEM analyses. It appears that the population of TDs having ±1/3<11-20>GaN type Burgers vectors is higher than that of the pure edge TDs with ±[0001]GaN type Burgers vectors . An optimized LT-AlN buffer layer thickness was found to enhance the near bandedge PL emission and quench the yellow luminescence of the non-polar GaN film.
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Huang, Po-yu, and 黃柏渝. "The photolysis difference between Polar and non-polar molecule in CH4-ice mixture." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/64394727286788084750.
Full textAbstract:
碩士國立中央大學
物理研究所
98
The astronomical observation in resent years shows that the main composition of those TNOs ice are H2O, CH4 and N2. We choose these species as the ice composition and compare their difference in reaction products after exposed to and altered by VUV photons. N2 : CH4 = 1 : 1, CH4 : H2O = 1 : 1 and N2 : CH4 : H2O = 1 : 1 : 1 mixtures were prepared in gas-phase before condensation on to a precooled (16K) substrate. We use the High Flux beamline at Synchrotron Radiation Research Cente as the VUV light source. New molecules produced during photolysis were identified on the basis of their characteristic infrared feature. Quadrupole mass spectrometer was employed to detect the desorbed products during ice warming. CH4 molecules being trapped within a comparably stable N2 species in the N2-containing ices. This will induce Matrix-isolated phenomenon which blocks the radicalradical interaction between CH3 molecules and reduces the destruction rate of CH4 durung photolysis. Therefore, less C2H6 and C3H8 reaction products were detected. Moreover, lots of H atoms detached form the CH4 molecures will recombine with CCCN molecules to form HNCCC. That’s why we can only find a weak Mid-IR absorbance band of CCCN at 2194 cm^-1, but a clear absorbance feature of HNCCC at 2205 cm^-1 wavenumber. We also used the hydrogen microwave discharge lamp as the VUV light souce in the laboratory(10.2 eV). And compare the reaction products difference with the High Flux beamline (4 ∼ 20 eV ) after solid N2 + CH4 + H2O mixtures were photolysized by them. However, we didn’t find any N-containing reaction products after the ice was photolyzed by hydrogen lamp. Supposedly, the hydrogen lamp already have enough photon energy to destruct the bonds in the N2 molecules which bonding energy is about 9.76 eV. After changing the experimental methodes by photolyzing and condensing the gas-phase mixtures onto the substrate at the same time, lots of new species and products yields are found by their IR feature. And the N-containing products also shown up in those products. So we infer that the bonding energy of N2 ice is higher than 10.2 eV at least. N2-containing ice was processed by UV-photons from the High Flux beamline light source. And we find the CN^-’s IR feature at 2082cm^-1 wavenumber. However, the product was only found during ice warming process in Moore and Hudson’s experiment. By comparing the behavior of the CN^-’s IR feature during warming, we confirmed that it’s the same species that also detected in Moore and Hudson’s experiment, and believe that the CN^- will forms after VUV photolysis, but the photochemistry procedurs still needs further study to confirm. There is also lots of Nitrile (R-CN) reaction products synthesized during N2 +CH4 mixtures were processed by UV-photons. However, if there are H2O in the ice mixtures. We can’t find any Nitrile or Isonitrile yields but OCN^- will show up instead. From the above results, we found that the non-polar molecules–N2 and the polar molecules–H2O will have different influences on the products of the CH4-containing ice after photolysis. By comparing to the astronomical observations and the related publications. We confirmed that those reactions and phenomenons occuring on the TNOs. The discoveries and analysis results in this work can be used as one of reference for TNOsrelated research and other ice simulated experiments in the future.
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Wu, Pei-Tsen, and 吳珮岑. "Physical properties of non-polar GaN films." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/64773875287850692593.
Full textAbstract:
碩士國立中興大學
物理學系所
96
In this thesis, the physical properties, particularly the dislocation characteristics, of non-polar gallium nitride (GaN) films were investigated. Non-polar GaN films were grown on (1-102) sapphire substrates by Metal organic chemical vapor deposition (MOCVD). The as-grown non-polar GaN films were investigated by θ-to-2θ X-ray diffractometry (XRD), photoluminescence (PL) spectroscopy, transmission electron microscope (TEM) and double-crystal rocking-curve XRD. The results of TEM observations indicate that the density of threading dislocations are very high in the non-polar GaN films, and most of them are mainly Shockley partial dislocations and mixed dislocations rather than pure edge and pure screw dislocations. This result is attributed to the large difference in lattice mismatch along[1-101]sapphire||[0001]GaN and [11-20]sapphire||[1-100]GaN directions so that lots of stacking faults with Shockley partial dislocations are formed during epitaxial growth.
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林薛智. "Generalized Equations for Second Virial Coefficient of Non-polar Fluids and Cross Second Virial Coefficient of Non-polar Mixtures." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/03992921846950679532.
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"Terahertz absorption in non-polar condensed matter systems." Thesis, 2010. http://hdl.handle.net/1911/61963.
Full textAbstract:
Terahertz time-domain spectroscopy (THz-TDS) is a powerful non-contact optical technique for characterizing materials and sub-picosecond dynamic behavior in the far-infrared region (100 GHz --- 10 THz) of the electromagnetic spectrum. As a young field (less than 25 years old), the terahertz spectral properties of many materials and physical processes remain unexplored. One of the most interesting, and fundamentally important, uncharacterized phenomena is the phase behavior of condensed matter systems. Normal ( n)-alkanes are molecules of particular interest since they are linear, straight-chain hydrocarbons that are structurally simple and have melting points near room temperature. Using a custom designed spectrometer and sample cell, we characterize the terahertz optical properties of various liquid branched and n-alkanes (C5H12 - C16H34) and use this as the basis to conduct imaging studies of a two-component surfactant/octane system to discern the content across the boundary layer. This prefaced our characterization of the phase behavior of longer n-alkanes where we observed novel temperature-dependent absorption features in the equilibrium non-liquid phases of n-tricosane (C23H48) through n-hexacosane (C26H54). These spectroscopic features have never previously been observed in non-polar (infrared inactive) materials, and provide new insight into the crystallization dynamics of organic molecular solids.
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Huang, Feng-wen, and 黃鋒文. "Characterization of non-polar InGaN/GaN optoelectronic devices." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/67714126808830813008.
Full textAbstract:
碩士國立成功大學
光電科學與工程研究所
96
This thesis aims at the research and fabrication of optical polarization anisotropy characteristics of light emission and absorption of optoelectronic devices fabricated on nonpolar A-plane InGaN/GaN materials. The optical polarization of light emission from the top surface and sidewall of the A- and C-plane InGaN/GaN multiple-quantum-well light-emitting diodes were investigated by measurement of polarized light power detection system and polarized electroluminescence. For the polarization of light absorption of photodetectors, the optical polarization of light absorption from the top surface of the polar C-plane and nonpolar A-plane GaN photodetectors were investigated by measurement of the responsivities for polarization detection system. The measurement of polarized light emission and absorption detection systems showed the optical polarization anisotropy characteristics of light emission from sidewall of the polar C-plane and nonpolar A-plane InGaN/GaN multiple-quantum-well light-emitting diodes, and light absorption from the top surface of the nonpolar A-plane GaN photodetectors. Furthermore, the polarization anisotropy characteristics of light emission and absorption can be enhanced by the modification of anisotropic strain and the device structure design.
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Montgomery, Steven J. "Synthesis of non-polar/hydrogen bonding block copolymers." 2003. http://etda.libraries.psu.edu/theses/approved/PSUonlyIndex/ETD-430/index.html.
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Su, Ching-Fu, and 蘇清富. "Synthesis and Characteristics of Non-polar Polyurethane Elastomer." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/71283016472271521900.
Full textAbstract:
碩士萬能科技大學
材料科技研究所
98
Nonpolar-based Polyurethane compared with polyester- and polyether-baesd Polyurethane, generally has superior hydrolytic stability, lower moisture permeability, higher oxidative stability, and improved low temperature. However, those Nonpolar-based Polyurethanes materials exhibit a lower tensile property because it is lack of strain-induced crystallization. In this study, a Nonpolar soft-segment containing polyurethane copolymer with hydrolytic and thermal stability will be synthesized using of two-step method. The results shown that the tensile strength of the copolymer was improved by the PCL polyol incorporated in the polyurethane copolymer that used PRIPLAST® as the soft segment. Furthermore, the copolymers have two characteristics of phase transition including the PRIPLAST® and PCL soft segments, and have three stages of degradation, which are associated with the soft and hard segment compositions for the phase transition and degradation.