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Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 55 for “"wurtzite"”.
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STUDY OF WURTZITE AND ZINCBLENDE GAN BASED GREEN LED HETEROSTRUCTURE
… focusses on the characterisation of conventional wurtzite (wz)-GaN based LEDs and novel zincblende (zb)-GaN based LEDs. The investigated wz-GaN based multiple quantum well structures have been found in other studies to have higher internal quantum efficiency (IQE) when the quantum wells (QWs) were …
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Pulsed laser ablation deposition and optical characterization of hexagonal-wurtzite silicon
Hexagonal-wurtzite silicon phase silicon is an unusual polymorph of silicon with potentially useful electro-optical properties. Previous studies using a simple deposition system demonstrated that laser ablation of the standard cubic-diamond silicon produces droplets containing hexagonal-wurtzite …
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Mechanisms of the Wurtzite to Rock Salt Phase Transitions in Galium Nitride
We studied the wurtzite to rock salt phase transition in gallium nitride ( GaN ). Using the mapping algorithm of COMSUBS we found 435 possible mechanisms for this transition. We then used FIREBALL to do density functional theory calculations and found enthalpy barrier heights for the transition …
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Probing Nanoscale Functional Properties of Perovskite and Wurtzite Ferroelectrics via Scanning Probe Microscopy
… and conductivity of perovskite and wurtzite ferroelectric materials for prospective applications in science and technology. Ferroelectrics exhibit a switchable spontaneous polarization when subjected to an electric field and are instrumental in developing low-energy nanoelectronics. …
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Semiconductor electronic band alignment at heterojunctions of wurtzite aluminum nitride, gallium nitride, and indium nitride
In this thesis the band alignments for wurtzite (0001) heterojunctions of AlN, GaN, and InN semiconductors are measured by x-ray photoemission spectroscopy. The bands alignments are all found to be Type I, and the valence-band discontinuities are found to be:(UNFORMATTED TABLE OR EQUATION …
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Growth of Wurtzite Gallium Nitride Epitaxial Films on Sapphire Substrate by Reactive Molecular Beam Epitaxy and Material Characterization
For the growth of n-type films, a specific ammonia flow rate (or V/III ratio if Ga flux is fixed) was required to obtain films with high electron Hall mobility. X-ray diffraction (XRD), photoluminescence (PL), cross-sectional transmission microscopy (XTEM) and deep level transient spectroscopy …
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Investigations of the gallium nitride, aluminum nitride and indium nitride semiconductors: Structural, optical, electronic and interfacial properties
… physical properties of both zincblende and wurtzite Group III - Nitride wide bandgap semiconductor materials. All of the thin films studied were grown by plasma-enhanced molecular beam epitaxy on either GaAs and SiC substrates. This growth method proved to be suitable for nitride expitaxial …
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Topics in semiconductor physics: Part I. Phonons in semiconducting alloys and alloy superlattices ; Part II. Deep energy levels of defects in mercury cadmium telluride and wurtzite semiconductors
… which have a narrow and variable band gap, and wurtzite semiconductors: AtN, CdS, CdSe, ZnS, and ZnO, which have large band gaps. A variety of defects responsible for trapping centers are identified. Our results would be instrumental in improving the quality of these technologically important …
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Characterisation of ScN and ScGaN alloys grown by Molecular Beam Epitaxy
The wurtzite III-nitrides AlN, GaN and InN are currently widely used in optoelectronic applications such as light-emitting diodes and this success is owed in large part to the possibility of band gap engineering by alloying between the constituent nitrides. Unfortunately, the restricted material …
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Multi-scale modelling of III-nitrides: from dislocations to the electronic structure
… from the literature to the specific case of wurtzite materials, (ii) to extend and summarise theoretical studies of the critical thickness in heteroepitaxy. Subsequently, (iii) to develop an improved geometrical model for threading dislocation density reduction during the growth of thick GaN …
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Structural, electronic and optical properties of cadmium sulfide nanoparticles
… underlying crystal structures (zincblende, wurtzite, rocksalt), particle shapes (spherical, cuboctahedral, tetrahedral), and saturations (unsaturated, partly saturated, completely saturated). For saturated particles, the calculated onset excitations are strong excitonic. The …
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A tight-binding analysis of the electronic properties of III-nitride semiconductors
… of atoms. We compare the zincblende and ideal wurtzite structures in terms of effective charges, spontaneous polarisation and piezoelectric coefficients, within a first nearest neighbour tight-binding model. We further compare these to real wurtzite structures and conclude that accurate …
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Synthesis, characterization, and biotemplated assembly of indium nitride and indium gallium nitride nanoparticles
… in organic solvents. These nanoparticles are wurtzite phase with a measured bandgap as low as 0.79 eV and average size of 6.2 nm. Based on this synthesis, indium-rich InGaN nanoparticles were synthesized and characterized. Chemical, structural, and optical analysis indicated up to 10% gallium …
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Structural Characterisation of Heteroepitaxial Zincblende Gallium Nitride
… fields that plague the commonly used c-plane wurtzite crystal structure. In this thesis, metastable zincblende GaN grown by metal-organic vapour phase epitaxy is stabilised on 3C-SiC/Si substrates with a miscut, ranging from 0° to 4°. Crystalline zincblende GaN nucleates as elongated islands …
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Diluted Magnetic Semiconductor Nanomaterials Fabrication by a Chemical Vapor Deposition Method
… nanowires and naorods are single crystalline wurtzite structure and possess a growth direction along the c axis. At 850 ºC, the most optimistic condition for ZnO crystal growth was obtained. At high reaction temperature 950ºC, Mn2+ were substitutionally doped into ZnO lattice, resulting in …
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Interplay of Electrical, Mechanical and Thermal Fields in III-N Nanostructures for LED Applications
… rates; (3) to model piezoelectricity in the wurtzite lattice, we have considered four different polarization models (based on the experimental /bulk and ab initio coefficients) in increased order of accuracy; (4) to study the origin and effects of these four competing internal fields on the …
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Síntese e caracterização de nanoestruturas de óxido de zinco por via úmida
… the synthesized ZnO nanoparticles had the pure wurtzite structure (zincite) and the mixed oxide sample has two phases, zincite and tenorite. All the materials are mesoporous and the specific surfaces obtained vary from 2 to 86m 2 /g. The crystallite size of the samples are range of 6 to 57nm …
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Theory of topological insulators and its applications
… spin-orbit coupling. As a break of this trend, wurtzite based nitrides are shown to possess 2D topological insulator states. The strong internal polarization of wurtzite crystal is used to invert the bands and create a 2D TI. ^ As an application of TIs, the current-voltage characteristics of a …
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Investigation of exciton dynamics and electronic band structure of InP and GaAs nanowires
… individual Zincblend GaAs/AlGaAs core-shell and Wurtzite InP nanowires (NWs) at low temperatures (10K).</p><p> GaAs/AlGaAs core-shell NWs were prepared by using Au catalyst-assisted metal organic chemical vapor deposition (MOCVD) method and a titanium-Sapphire laser was used to excite the …
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Experimental and DFT study on selective oxidation of 5-Hydroxymethyl furfural over cadmium sulfide catalyst
… HMF on CdS surface is calculated for hexagonal wurtzite and simple cubic crystal structure of CdS catalyst which indicate capability of CdS as a catalyst for HMF oxidation.
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