Dissertations / Theses: 'Electronic semiconductor'

1

Newson, D. J. "Electronic transport in III-V semiconductors and semiconductor devices." Thesis, University of Cambridge, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382242.

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Tallarida, Massimo. "Electronic properties of semiconductor surfaces and metal, semiconductor interfaces." [S.l.] : [s.n.], 2005. http://www.diss.fu-berlin.de/2005/196/index.html.

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Wharam, David Andrew. "Electronic transport in semiconductor microstructures." Thesis, University of Cambridge, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.315922.

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4

Kelly, Leah L. "Electronic Structure and Dynamics at Organic Semiconductor / Inorganic Semiconductor Interfaces." Diss., The University of Arizona, 2015. http://hdl.handle.net/10150/566997.

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In this dissertation, I present the results of my research on a prototypical interface of the metal oxide ZnO and the organic semiconductor C₆₀. I establish that the physics at such oxide / organic interfaces is complex and very different from the extensively investigated case of organic semiconductor / metal interfaces. The studies presented in this dissertation were designed to address and improve the understanding of the fundamental physics at such hybrid organic / inorganic interfaces. Using photoemission spectroscopies, I show that metal oxide defect states play an important role in determining the interfacial electronic properties, such as energy level alignment and charge carrier dynamics. In particular, I show that for hybrid interfaces, electronic phenomena are sensitive to the surface electronic structure of the inorganic semiconductor. I also demonstrate applications of photoemission spectroscopies which are unique in that they allow for a direct comparison of ultrafast charge carrier dynamics at the interface and the electronic structure of defect levels. The research presented here focuses on a achieving a significant understanding of the realistic and device relevant C₆₀ / ZnO hybrid interface. I show how the complex surface structure of ZnO can be modified by simple experimental protocols, with direct and dramatic consequences on the interfacial energy level alignment, carrier dynamics and carrier collection and injection efficiencies. As a result of this careful study of the electronic structure and dynamics at the C₆₀ / ZnO interface, a greater understanding of the role of gap states in interface hybridization and charge carrier localization is obtained. This dissertation constitutes a first step in achieving a fundamental understanding of hybrid interfacial electronic properties.

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Richards, David Robert. "The electronic structure and optical properties of GaAs two-dimensional electron systems." Thesis, University of Cambridge, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.359697.

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Oliveira, Miguel Afonso Magano Hipolito De Jesus. "Electronic properties of layered semiconductor structures." Thesis, Imperial College London, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.406392.

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Charlesworth, Jason. "Electronic structure of metal-semiconductor interfaces." Thesis, University of Cambridge, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239738.

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Peleckis, Germanas. "Studies on diluted oxide magnetic semiconductors for spin electronic applications." Access electronically, 2006. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20070821.145447/index.html.

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9

Brocke, Thomas. "Electronic Raman spectroscopy on semiconductor quantum dots." Göttingen Cuvillier, 2007.

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Marsh, A. C. "The electronic properties of semiconductor heterojunction systems." Thesis, University of Cambridge, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.372890.

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O'Sullivan, Eoin. "Electronic states and dynamics in semiconductor structures." Thesis, University of Oxford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325987.

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Barker, James Alexander. "The electronic properties of semiconductor quantum dots." Thesis, University of Surrey, 2000. http://epubs.surrey.ac.uk/1021/.

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Burdis, Mark Samuel. "Electronic conduction processes low-dimensional semiconductor systems." Thesis, University of Exeter, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.235999.

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Said, Elias. "Electrolyte : Semiconductor Combinations for Organic Electronic Devices." Doctoral thesis, Linköpings universitet, Institutionen för teknik och naturvetenskap, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-15775.

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The discovery of semi-conducting organic materials has opened new possibilities for electronic devices and systems because of their solution processibility, lightweight and flexibility compared to inorganic semiconductors. The combination of semiconductors with electrolytes, and more especially organic semiconductors and solid electrolytes has attracted the attention of researchers because of the multiple phenomena originating from the simultaneous motion of electrons and ions. This thesis deals with organic-based devices whose working mechanism involves electrolytes. By measuring electrochromism induced by the field in isolated segments of conjugated polymer films, which is in contact with an electrolyte, the direction and the magnitude of the electric field along an electrolyte is quantified (paper I). In addition, using a polyanionic proton conductor in organic field-effect transistor (OFET) as gate dielectric results in low operation voltage and fast response thanks to the high capacitance of the electric double layer (EDLC) that is formed at organic semiconductor/ polyelectrolyte interface (paper III). Because an electrolyte is used as a gate insulator, the effect of the ionic currents on the performance of an EDLC-OFET has been investigated by varying the relative humidity of the device ambience (paper IV). Since the EDLC-OFET and the electrochromic display cell both are operated at low voltages, the transistor has been monolithically integrated with an electrochromic pixel, i.e. combining a solid state device and an electrochemical device (paper V). Further, a theoretical study of the electrostatic potential within a so called pen-heterojunction made up of two semi-infinite, doped semiconductor media separated by an electrolyte region is reported (paper II).

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Blumenfeld, Michael Lewis. "LOCAL ELECTRONIC PROPERTIES OF ORGANIC SEMICONDUCTOR INTERFACES." Diss., The University of Arizona, 2010. http://hdl.handle.net/10150/194860.

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Understanding organic semiconductor interfaces is critical to developing organic photovoltaics (OPV). OPV interfaces are disordered due to weak intermolecular interactions, resulting in diverse charge transfer micro-environments. I present experimental data isolating high-order intermolecular interactions controlling interfacial energy level alignment and describe new instrumental capabilities providing access to the local electronic and kinetic landscape at organic semiconductor interfaces. Interface formation between vanadyl naphthalocyanine (VONc) and highly ordered pyrolytic graphite (HOPG) is investigated. Ultraviolet photoemission spectroscopy (UPS) shows that the VONc binding energy (BE) decouples from the work function, shifting in an opposite direction and contradicting the standard interface dipole model. This effect is quantitatively described using an electrostatic depolarization model and confirmed by simulations which show an inhomogeneous potential at the interface. New data and literature values suggest orthogonality between polarizability and molecular dipole in polar porphyrazines. Their potential for interface engineering is discussed. The electron-rich Au(111)/VONc interface is investigated. The organic layer induces a large interface dipole in Au(111) which can be fit to a depolarization model. Ionization potential and depolarization data suggest that the second VONc layer on Au(111) adopts a tilted geometry. Electrostatic differences between Au(111)/VONc and HOPG/VONc are discussed, demonstrating that interface dipole contributions are not interchangeable. The surface states of the Au(111)/VONc interface are characterized by angle resolved 2-photon photoemission to determine the magnitude of the perturbation. The measured free-electron-like effective mass and BE destabilization of the Shockley state is attributed to step edges caused by lifting the Au(111) (22 x √3) reconstruction. The Shockley state is accessible primarily through resonance with the n = 1 image state. Another resonance between the image state and a molecular state of VONc is tentatively identified. Design and construction of a confocal fluorescence microscope capable of single molecule detection in ultrahigh vacuum is described. Initial images and fluorescence trajectories demonstrate the ability to measure charge transfer kinetics between an individual organic semiconductor molecule and well-characterized insulating surfaces. Progress towards completion of a scanning photoionization microscope is presented. The microscope demonstrates diffraction-limited imaging capabilities using fs-laser-generated photoelectron current as contrast. Recommendations are given towards achieving spectral resolution and for future experimental systems.

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Zhang, Jiawei. "Oxide-semiconductor-based thin-film electronic devices." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/oxidesemiconductorbased-thinfilm-electronic-devices(c8cde776-b68b-47b5-ab63-382a86dbb94b).html.

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Oxide semiconductors have been envisaged to find applications in ubiquitous flexible electronics in daily life such as wearable electronic gadgets to offer novel user experiences. However, one of the bottlenecks to realise these applications is a lack of oxide-semiconductor components capable of wireless communications. As Bluetooth and Wi-Fi are the two dominant communication interfaces, fast enough front-end rectifiers must be developed to operate at their gigahertz (GHz) transmission frequencies. Furthermore, despite of significant developments of n-type oxide semiconductors in the last decade, widespread flexible electronics also requires high-performance p-type oxide semiconductors for use in complementary logic circuits. The objectives of this dissertation are to develop high quality Schottky barriers, achieve GHz speed Schottky diodes on rigid and flexible substrates, evaluate the noise properties of the Schottky diodes, develop p-type oxide semiconductor using sputtering technology, elucidate the hole transport mechanism in p type transistors, and demonstrate their potential applications such as radio receivers, complementary inverters and ring oscillators. First, indium gallium zinc oxide (IGZO) Schottky diodes were fabricated by using radio frequency magnetron sputtering. The oxygen content at the metal-IGZO interface was found to have a profound effect on the electrical performance. By introducing 3% O2 during the deposition of Pt or IGZO, the diodes exhibited excellent electrical properties without requiring any annealing treatment, thus allowing for the realisation of flexible IGZO Schottky diodes. The high-frequency properties of Pt-IGZO Schottky diodes on glass substrates were optimised by testing a range of IGZO thicknesses and diode active areas. The achieved highest cut-off frequency was beyond 20 GHz, which is to the best of our knowledge the fastest oxide-semiconductor device to date. On flexible substrates, the diodes also showed cut-off frequencies up to 6.3 GHz, well beyond the critical benchmark speed of 2.45 GHz for typical wireless communications. In order to assess the feasibility of using IGZO Schottky diodes in practical applications, measurements were taken to discern their low-frequency noise properties. In the as-deposited diodes, logarithmic dependence of the noise spectral density on the applied bias was observed, revealing that the dominant noise was generated in the space-charge region at low biases and in the series-resistance region at high biases, respectively. After annealing the diodes, very different noise mechanism was observed and the interface-trap-induced noise dominated the noise spectra. As one of the most promising p-type oxide semiconductors, SnO was also studied at low temperatures in this thesis. The experiment revealed that hole-transport mechanism was governed by either band conduction or variable range hopping in different temperature ranges. Finally, the potential for fully oxide-based electronics was demonstrated by an amplitude-modulation radio receiver comprising of an IGZO Schottky diode as the demodulator and a complementary ring oscillator based on IGZO and SnO transistors. In reference to IEEE copyrighted material which is used with permission in this thesis, the IEEE does not endorse any of the University of Manchester's products or services. Internal or personal use of this material is permitted. If interested in reprinting/republishing IEEE copyrighted material for advertising or promotional purposes or for creating new collective works for resale or redistribution, please go to http://www.ieee.org/publications_standards/publications/rights/rights_link.html to learn how to obtain a License from RightsLink.

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Bode, Christopher Allen. "Run-to-run control of overlay and linewidth in semiconductor manufacturing." Digital version:, 2001. http://wwwlib.umi.com/cr/utexas/fullcit?p3008281.

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18

Milward, Jonathan Ray. "Electronic optical nonlinearities in ZnSe." Thesis, Heriot-Watt University, 1991. http://hdl.handle.net/10399/858.

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Wolverson, D. "Optical and electronic properties of disordered semiconductors." Thesis, University of Exeter, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379465.

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20

Gilbert, Timothy George. "Electronic states of ultrathin GaAs/AlAs superlattices." Thesis, University of Leicester, 1988. http://hdl.handle.net/2381/35893.

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The continuing refinement of crystal growth techniques has made possible the fabrication of semiconductor superlattices where the period can be as small as one lattice constant. Prediction of many of the properties of such systems requires a detailed description of their electronic structure. In this thesis, a self-consistent pseudopotential method which includes a parametrization scheme has been used to calculate the electronic properties of (GaAs)n(AlAs)n superlattices with n ranging from 1 to 4. The parametrization scheme is used to reproduce energy gaps at the principal symmetry points for the bulk constituents and the resulting parameter set is employed in all subsequent calculations. The n=l superlattice is found to be indirect with the conduction band minimum at R (equivalent to the zincblende L point) and all the thicker systems are pseudodirect in good agreement with experimental results. The lowest conduction band state at the zone centre for all systems is found to be mainly X-derived reflecting the importance of zone translating effects here. By analysing the states near to the band edges, the observed pattern of confinement in states of the n=l superlattice shows the band offsets to have at most a small role, in contrast to the thicker systems where a definite relationship was established. Moreover, the results suggest that Dingle's "15% rule" is consistently violated and that a valence band offset of about 30-40% is obtained which changes little with layer thickness. Attempts to study the effects of hydrostatic pressure on the n=3 superlattice were in part successful and predicted quite complex behaviour for the electronic states. Much of the discrepancy between the results obtained and the experimental data was attributed to the inadequacies of the empty-core pseudopotential to model the ions.

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Sharma, Adesh. "Electronic transport in GaAs-AlGaAs heterostructures." Thesis, University of Cambridge, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239264.

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22

Hessami, Pilehrood Saeid. "Electronic properties of semiconductor nanostructures under terahertz radiation." Access electronically, 2006. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20061026.162405/index.html.

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23

Hughes, D. T. "Electronic states in semiconductor superlattices and quantum wells." Thesis, Durham University, 1989. http://etheses.dur.ac.uk/6519/.

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The aim of this thesis is two-fold. Firstly to show how a complex bandstructure matching technique has been developed which allows detailed investigations to be made of various low dimensional structures. Secondly the method will be used to investigate interesting physical properties of quantum wells and superlattices. Consequently the thesis will begin with an exposition of the matching technique, giving an indication of the numerical methods used for computational calculations. Evidence will then be given, in the form of a comparison between the present work and the experimental and theoretical results to be found in the literature, of the efficacy of the method. A detailed description of results of calculations carried out on the valence band of AlAs/GaAs and AlGaAs/GaAs quantum wells will show how energy levels and wavefunctions have been calculated as well as giving an explanation of hybridisation and anti-crossing effects. In order to extend the method to strained systems it will be shown how strain can be incorporated into the model by simple empirical fits of calculated bulk properties to experiment. This method will be used to model two particular Si/Ge structures: a Ge(_0.25)Si(_0.75)/Si/Ge(_0.25)Si(_0.75) quantum well and a (Si)(_4)(Ge)(_4) superlattice. To allow a better comparison with experiment for the superlattice a description is given of a method for calculating optical matrix elements between superlattice states; and the results of such calculations are discussed.

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Coles, Richard A. "Theory of the electronic states of semiconductor heterostructures." Thesis, Durham University, 1999. http://etheses.dur.ac.uk/4495/.

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This thesis is concerned with theoretical calculations of the properties of electronic bound states in semiconductor heterostructures. The complex band structure empirical pseudopotential method (EPM) is used as the foundation of the work. Spin orbit coupling and strain effects (due to lattice mismatch) are included in familiar ways, as is the transfer matrix method, allowing the study of arbitrarily configured heterostructures. These techniques are used to investigate the unusually deep InAs/AlSb conduction band well. The strong possibility of intraband transitions at electro magnetic wavelengths around 1.55µm is predicted, with corresponding enhanced momentum matrix elements and joint density of states over interband transitions. An InAs/GaSb/AlSb asymmetric well is investigated, paying particular attention to the bound states in the vicinity of the InAs/GaSb band overlap. The electron-like states are found to cross with heavy hole and anti-cross with light hole-like states, as a function of heterostructure dimension or applied electrostatic field. This is analogous to the hybridisation of states in the in-plane band structure, except that for zero in-plane wave vector there can be no appreciable hybridisation of electron and heavy hole states. A technique is described that has been developed to extract envelope functions from heterostructure wavefunctions calculated using the realistic complex band structure EPM approach. These envelope functions conform to Burt’s theory (M. G. Burt, J. Phys.: Condens. Matt. 4, 6651 (1992)) in that they are uniquely defined, continuous and smooth over all space. Comparisons with traditional effective mass envelope functions are made. The extracted envelope functions are used to demonstrate conclusively Burt's predictions (M. G. Burt, Superlatt. Mi- crostruct. 17, 335 (1995)) concerning the inadequacy of certain approximations for the calculation of interband dipole matrix elements and charge oscillation. Finally, the issue of k • p operator ordering is convincingly settled, in favour of 'ordered' over 'symmetrised' Hamiltonians, by comparison to EPM calculations, and using EPM derived k • p parameters.

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Oloumi, Mahmoud. "Electronic structure and band offsets in semiconductor heterostructures." Thesis, Cardiff University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.314685.

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Goble, Nicholas James. "ELECTRONIC TRANSPORT AT SEMICONDUCTOR AND PEROVSKITE OXIDE INTERFACES." Case Western Reserve University School of Graduate Studies / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=case1454002713.

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Lincoln, Derek M. "The electronic structure and field effects of an organic-based room temperature magnetic semiconductor." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1193833038.

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Galeriu, Calin. "kp Theory of Semiconductor Nanostructures." Digital WPI, 2005. https://digitalcommons.wpi.edu/etd-dissertations/411.

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"The objective of this project was to extend fundamentally the current kp theory by applying the Burt-Foreman formalism, rather than the conventional Luttinger-Kohn formalism, to a number of novel nanostructure geometries. The theory itself was extended in two ways. First in the application of the Burt-Foreman theory to computing the momentum matrix elements. Second in the development of a new formulation of the multiband kp Hamiltonian describing cylindrical quantum dots. A number of new and interesting results have been obtained. The computational implementation using the finite difference method of the Burt-Foreman theory for two dimensional nanostructures has confirmed that a non-uniform grid is much more efficient, as had been obtained by others in one dimensional nanostructures. In addition we have demonstrated that the multiband problem can be very effectively and efficiently solved with commercial software (FEMLAB). Two of the most important physical results obtained and discussed in the dissertation are the following. One is the first ab initio demonstration of possible electron localization in a nanowire superlattice in a barrier material, using a full numerical solution to the one band kp equation. The second is the demonstration of the exactness of the Sercel-Vahala transformation for cylindrical wurtzite nanostructures. Comparison of the subsequent calculations to experimental data on CdSe nanorods revealed the important role of the linear spin splitting term in the wurtzite valence band."

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Greene, John Rausch. "Inquiry of Graphene Electronic Fabrication." DigitalCommons@CalPoly, 2016. https://digitalcommons.calpoly.edu/theses/1671.

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Graphene electronics represent a developing field where many material properties and devices characteristics are still unknown. Researching several possible fabrication processes creates a fabrication process using resources found at Cal Poly a local industry sponsor. The project attempts to produce a graphene network in the shape of a fractal Sierpinski carpet. The fractal geometry proves that PDMS microfluidic channels produce the fine feature dimensions desired during graphene oxide deposit. Thermal reduction then reduces the graphene oxide into a purified state of graphene. Issues arise during thermal reduction because of excessive oxygen content in the furnace. The excess oxygen results in devices burning and additional oxidation of the gate contacts that prevents good electrical contact to the gates. Zero bias testing shows that the graphene oxide resistance decreases after thermal reduction, proving that thermal reduction of the devices occurs. Testing confirms a fabrication process producing graphene electronics; however, revision of processing steps, especially thermal reduction, should greatly improve the yield and functionality of the devices.

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Fix, Aaron. "Synthesis and Properties of Indenofluorene and Diindenothiophene Derivatives for Use as Semiconducting Materials in Organic Electronic Devices." Thesis, University of Oregon, 2013. http://hdl.handle.net/1794/13444.

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Organic electronic devices are becoming commonplace in many academic and industrial materials laboratories, and commercial application of these technologies is underway. To maximize our fundamental understanding of organic electronics, a wide array of molecular frameworks is necessary, as it allows for a variety of optical and electronic properties to be systematically investigated. With the ability to further tune each individual scaffold via derivatization, access to a broad spectrum of interesting materials is possible. Of particular interest in the search for organic semiconducting materials are the cyclopenta-fused polyaromatic hydrocarbons, including those based on the fully conjugated indenofluorene (IF) system, which is comprised of five structural isomers. This dissertation represents my recent contributions to this area of research. Chapter I serves as a historical perspective on early indenofluorene research and a review of more current research on their synthesis and applications in organic electronic devices. Chapters II and III cover our early work developing the synthesis of the fully-reduced indeno[1,2-b]fluorene scaffold, with the latter of these chapters showing the first example of its application in an organic electronic device, a field effect transistor. Chapter IV demonstrates the first syntheses of fully-reduced indeno[2,1-c]fluorene derivatives. Chapter V expands our research to encompass isoelectronic heteroatomic derivatives of that same scaffold, introducing the fully-reduced diindeno[2,1-b:1',2'-d]thiophene scaffold and showing that our synthetic methodology also can be used to produce a quinoidal thiophene core. Chapter VI concludes with a review of the similarities between the indeno[2,1-c]fluorene and diindeno[2,1-b:1',2'-d]thiophene molecular architectures and introduces benzo[a]indeno[2,1-b]fluorene derivatives, demonstrating the first example of a fully-reduced indenofluorene that possesses a non-quinoidal core, illustrating that the quinoidal core is not a prerequisite for the strong electron affinities seen across the families of fully-reduced indenofluorenes. This dissertation encompasses previously published and unpublished co-authored material.<br>2015-10-10

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Remler, Dahlia Karin. "Ion dynamics in semiconductors with self-consistent electronic densities." Thesis, University of Oxford, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329985.

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Rad, M. Goshtasbi. "Electronic structure and reactions at some tetrahedral semiconductor surfaces /." Stockholm : Tekniska högsk, 2000. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3069.

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Blömers, Christian [Verfasser]. "Electronic transport in narrow-gap semiconductor nanowires / Christian Blömers." Aachen : Hochschulbibliothek der Rheinisch-Westfälischen Technischen Hochschule Aachen, 2013. http://d-nb.info/1033849812/34.

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Parkinson, Patrick. "Ultrafast electronic processes at nanoscale organic-inorganic semiconductor interfaces." Thesis, University of Oxford, 2009. http://ora.ox.ac.uk/objects/uuid:e68168c6-bcc0-437d-9133-1bfaf955c80a.

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This thesis is concerned with the influence of nanoscale boundaries and interfaces upon the electronic processes that occur within both organic and inorganic semiconductors. Photoluminescent polymers, highly conducting polymers and nanoscale inorganic semiconductors have been investigated using state-of-the-art ultrafast optical techniques, to provide information on the sub-picosecond photoexcitation dynamics in these systems. The influence of dimensionality on the excitation transfer dynamics in a conjugated polymer blend is studied. Using time-resolved photoluminescence spectroscopy, the transfer transients both for a three-dimensional blend film, and for quasi-two-dimensional monolayers formed through intercalation of the polymer blend between the crystal planes of a SnS2 matrix have been measured. A comparison of the experimental data with a simple, dimensionality-dependent model is presented, based on point dipole electronic coupling between electronic transition moments. Within this approximation, the energy transfer dynamics are found to adopt a three-dimensional character in the solid film, and a two-dimensional nature in the monolayers present in the SnS2 -polymer nanocomposite. The time-resolved conductivity of isolated GaAs nanowires has been investigated by optical-pump terahertz-probe time-domain spectroscopy. The electronic response exhibits a pronounced surface plasmon mode that forms within 300 fs, before decaying within 10 ps as a result of charge trapping at the nanowire surface. The mobility has been extracted using the Drude model for a plasmon and is found to be remarkably high, being roughly one third of that typical for bulk GaAs at room-temperature and indicating the high quality and low bulk defect density in the nanowires studied. Finally, the time-resolved conductivity dynamics of photoexcited polymer-fullerene bulk heterojunction blends for two model polymers, P3HT and MDMO-PPV, blended with PCBM are presented. The observed terahertz-frequency conductivity is characteristic of dispersive charge transport for photoexcitation both at the π−π* absorption peak (560 nm for P3HT), and significantly below it (800 nm). The photoconductivity at 800 nm is unexpectedly high, which is attributed to the presence of a charge transfer complex. In addition, the excitation-fluence dependence of the photoconductivity is studied over more than four orders of magnitude. The time-averaged photoconductivity of the P3HT:PCBM blend is over 20 times larger than that of P3HT, indicating that long-lived positive polarons are responsible for the high photovoltaic efficiency of polymer:fullerene blends. At early times (~ ps) the linear dependence of photoconductivity upon fluence indicates that interfacial charge transfer dominates as an exciton decay pathway, generating charges with mobility of at least ~0.1cm2 V−1 s−1. At later times, a sub-linear relationship shows that carrier-carrier recombination effects influence the conductivity on a longer timescale (> 1 μs).

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Gell, Michael A. "Electronic and optical properties of III-V semiconductor superlattices." Thesis, University of Newcastle Upon Tyne, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.352920.

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Sabathil, Matthias. "Opto-electronic and quantum transport properties of semiconductor nanostructures /." Garching : Verein zur Förderung des Walter Schottky Instituts der Technischen Universität München, 2005. http://www.loc.gov/catdir/toc/fy1002/2008380872.html.

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Lew, Albert Yuet-Sang. "Atomic-scale structural and electronic properties of semiconductor heterostructures /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 1997. http://wwwlib.umi.com/cr/ucsd/fullcit?p9732711.

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Zbydniewska, Ewa. "Electronic properties of coupled semiconductor nanocrystals and carbon nanotubes." Thesis, Lille 1, 2016. http://www.theses.fr/2016LIL10010/document.

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Ce travail de thèse décrit les propriétés électroniques de nanodispositifs couplés entre transistors à nanotubes de carbone (CNTFETs) et nanocristaux semiconducteurs colloïdaux CdSe/ZnS individuels en régime de détection de charge unique à température ambiante. Les transferts de charges élémentaires entre nanotubes et nanocristaux sont mis en évidence par les fluctuations temporelles du courant des transistors à tension de grille fixée, et font apparaître un signal à deux niveaux (bruit télégraphique ou RTS), observé sur des échelles de temps entre 1s et 0.1 ms. Les temps d’occupation τ des niveaux de courant suivent une loi de puissance P(τ)~τ-α où l’exposant α varie entre 1.5 et 4 (typiquement proche de 2.8). Cette observation suggère que les fluctuations de charges observées sont à la base des phénomènes de "clignotement optique" des nanocristaux colloïdaux étudiés. L’analyse spectroscopique des dispositifs permet d’attribuer ce clignotement à des pièges dans la bande interdite des nanocristaux, avec une énergie de chargement Ec de l’ordre de 200 meV. L’approche présentée dans ce travail peut être étendue à des mesures électro-optiques, et donc permettre une meilleure compréhension des phénomènes physiques contrôlant les propriétés optoélectroniques de nanodispositifs à base de nanocristaux semiconducteurs<br>We study the electronic properties of coupled semiconductor nanocrystals and carbon nanotubes. We report measurements of single electron transfers between single CdSe colloidal nanocrystal coupled to a carbon nanotube field effect transistor at room temperature in ambient conditions. The measurements consist of nanotube current level monitoring as a function of time for fixed gate voltage. We observe a sequence of high - low currents (random telegraph signal) on time scales up to several seconds with ms sampling time. We attribute the two level current fluctuations to the transfer of single electron onto the nanocrystal. The probability of the occupation time τ at the high or low current state follows a power law of the form P(τ)~τ-α where exponent α lies between 1.5 and 4 (typically close to 2.8). The observation suggests that the two-level current switching is similar to the fluorescence intermittency (optical blinking) observed in individual quantum dots. The spectroscopic analysis of the devices based on coupled semiconductor nanocrystals and carbon nanotubes is consistent with the charging of nanocrystal defect states with a charging energy of Ec ~ 200 meV. The approach developed here enables to probe the trap state dynamics in quantum dots in ambient air and room temperature from a purely electrical approach, and therefore to better understand the physics at hand in (opto)electronic devices based on quantum dots

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39

Bull, Michael. "Models of electronic defects at the Si-SiOâ†2 interface." Thesis, University of Oxford, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.237868.

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40

Whittington, Geoffrey. "Studies of electronic conduction in some small GaAs based samples." Thesis, University of Nottingham, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.235960.

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41

Royo, Valls Miquel. "Theoretical modelling of electrons and holes in semiconductor nanostructures." Doctoral thesis, Universitat Jaume I, 2010. http://hdl.handle.net/10803/669140.

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En esta tesis se utiliza la aproximación de masa efectiva y función envolvente para estudiar teóricamente las propiedades optoelectrónicas de una gran variedad de nanoestructuras semiconductoras, muchas de las cuales son obtenibles en un laboratorio a día de hoy. El primer capítulo de la tesis se centra en el estudio de los efectos derivados de aplicar campos magnéticos externos sobre varias nanoestructuras formadas por anillos cuánticos: dos anillos acoplados lateralmente y verticalmente, y una red periódica bidimensional de anillos. El segundo capítulo constituye la parte más extensa e importante de la tesis y estudia la influencia del entorno dieléctrico sobre las propiedades optoelectrónicas de nanocristales sintetizados mediante técnicas de química coloidal con forma esférica y alargada. Mediante cálculos multipartícula basados en las metodologías DFT y CI, se estudia el efecto del confinamiento dieléctrico sobre nanocristales poblados con un alto número de electrones o con pares electrón hueco. Finalmente, el último capítulo de la tesis se centra en el estudio de los estados multipartícula y las transiciones de fase a lo largo de un proceso en el que un nanocristal esférico es alargado hasta formar una estructura casi unidimensional.

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42

Morrison, I. "The electronic and optical properties of silicon/germanium strained layer superlattices." Thesis, University of Newcastle Upon Tyne, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379340.

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43

Beavis, A. W. "Electronic and optical properties of perfect and imperfect II-VI superlattices." Thesis, University of Newcastle Upon Tyne, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293542.

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44

Hong, Boon Hon. "Modelling of semiconductor nanostructures : electronic properties and simulated optical spectra." Thesis, University of Hull, 2011. http://hydra.hull.ac.uk/resources/hull:5126.

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III-V semiconductor nanostructures are widely used in optoelectronic devices (e.g. lasers and detectors) in the visible (0.4-0.8 μm), near-infrared (0.8-3 μm), mid-infrared (3-5 μm) and far-infrared (> 8 μm) wavelength ranges, with great potential for high performance and high temperature operation. As well as simple designs, complex structures incorporating low dimensional components (e.g. quantum wells and quantum dots) are not unusual. Often, the optical and electronic characteristics of these structures are altered significantly as compared to bulk material. As a prerequisite to design for different applications, the study of their electronic and optical properties is essential. With the increasing computational power of modern personal computers, computational modelling becomes viable and more efficient. Indeed, it has become routine to follow (or to precede) experimental studies with computational modelling of good interpretive and predictive power. Combined with experimental studies, this is a powerful tool to provide insight into new devices. This research work is primarily based on calculations of the electronic band structure of various semiconductor nanostructures, followed by modelling of optical transitions and optical spectra. All numerical calculations use a cost effective computational method. The applicability of the model to ultra-thin structures of short period InAs/GaSb superlattices is investigated. The work is then extended to study complex quantum-dot-in-well structures. Finally, the attempt to extract the structural parameters of quantum dots by a combination of modelling and optical spectroscopy is presented.

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45

Huang, Ya-shih. "Electronic structure of interfacial states formed at polymeric semiconductor heterojunctions." Thesis, University of Cambridge, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.604702.

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This thesis focuses on the nature and role of interfacial states formed at the heterojunctions between polymer donor and polymer acceptor systems. Two classes of organic semiconductors are investigated: (1) conjugated polymers, poly (9,9-dioctylfluorene-co-bis-N,N-(4-butylphenyl)-bis-N,N-phenyl-1,4-phenylenediamine) (PFB) with poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT), and poly(9,9-dioctylfluorene-co-N-(4-butylphenyl)diphenylamine) (TFB) with F8BT, and (2) helical supra-molecular assemblies of copolymers consisting of the Pt-porphyrin and perylene chromophores. First, a molecular model is developed to describe such interfacial excited electronic excitations. It is found that for stable ground-state geometries, the excited state has a strong charge-transfer character. Furthermore, when partly covalent, modelled radiative lifetimes (~10<sup>-7</sup>s) and off-chain axis polarisation (30°) matched observed ‘exciplex’ emission. Additionally for the PFB:F8BT blend, geometries with fully ionic character are also found thus accounting for the low electroluminescence efficiency of this system. Second, the interchain and intrachain interactions are disentangled by systematically varying the interchain distance and extent of planarisation – two primary parameters that change with applied pressure. It is shown that the photophysical properties of these interfacial excited states are determined by the tradeoff between the electronic couplings and the energy mismatch between the charge-transfer and locally excited excitations upon reducing the interchain distance. In addition, increasing planarisation yields a decreased energy mismatch and a larger mixing from the locally excited excitations. Finally, a well-defined, close-packing multi-chromophoric system is investigated using a variety of optical spectroscopy techniques. The photophysical processes taking place in the system are found to strongly depend on which component of the copolymer is excited.

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Cusack, Mark Alexander. "Electronic and optical properties of semiconductor quantum wells and dots." Thesis, University of Newcastle Upon Tyne, 1996. http://hdl.handle.net/10443/1039.

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The influence of structural size and geometry on the electronic states, optical transitions and nonlinear optical response in semiconductor quantum wells and dots has been investigated. A quantum mechanical theory of optical nonlinearities in semiconductors has been used in conjunction with the empirical pseudopotential band structure method to determine the structural parameters leading to optimum second harmonic generation in p-type asymmetric GaAs/AlxGa₁₋xAs quantum well structures. Maximum confinement of all participating states is of paramount importance for optimising such responses. The multi-band effective mass approximation was adapted for the calculation of the electronic structure and optical transitions in cubic GaAs/AlAs quantum dots and in the recently discovered InAs/GaAs self-assembled structures. The calculation revealed the importance of factors such as the quantum mechanical mixing between bulk basis states, inhomogeneous strain and symmetry in the construction of the optical signatures of these dots.

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47

Walker, Darren John. "The electronic and optical properties of some novel semiconductor nanostructures." Thesis, University of Nottingham, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.479333.

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Dahir, Hadi Mohammed. "An investigation of continuous-time electronic filters for semiconductor integration." Thesis, University of Bradford, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.281119.

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Birkett, M. J. "Opto-electronic studies of semiconductor tunnelling structures and quantum wells." Thesis, University of Sheffield, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267179.

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Amthong, Attapon. "Electronic states in externally modulated dilute magnetic semiconductor/superconductor hybrids." Thesis, University of Bath, 2012. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.563997.

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Dilute magnetic semiconductors (DMSs) are attractive. They are candidate materials for applications in novel spintronic devices. Because of the giant Zeemaneect in the paramagnetic state, a magnetic eld can be used to manipulate the spin and charge of carriers in DMSs. One possibility is to exploit the nonhomogeneous magnetic elds due to superconductors. In this thesis, the heterostructures of the planar DMS and superconductors in dierent geometries and superconducting states are investigated to understand the electronic structure of electrons in the DMS. The combination of a superconducting disk in the Meissner state and the planar DMS is studied using both simple and realistic models of the magnetic eld associated with the disk. The giant Zeeman interaction is found to substantially inuence the energies of magnetically conned states in the adjacent DMS. In the simple model eld, the giant Zeeman energy acts as an extra conning potential and results in spin dependent electron states exhibiting dierent spatial distributions, while the more realistic model eld results in conned states exhibiting a variety of mixed spin characters. The hybrid of a superconducting lm in a superconducting vortex state and the DMS is then explored. The concentrated magnetic eld due to an isolated vortex is shown to trap strongly spin polarised electron states. In the case of an Abrikosov lattice of vortices, interactions between vortex-bound states result in a band structure which can be controlled by the magnitude of an external uniform magnetic eld. It is found that the numerical band structures obtained using a basis of Landau states dier from those previously reported, leading to the development of a tight-binding theory to conrm their corrections. Another hybrid investigated is a square superconductor above the DMS. In this case, the arrangement of vortices is distorted by the boundary of the sample, leading to the possibility of multivortex state and/or giant vortex states. It is discovered that the magnetic eld due to the former state induces \molecular" electron states in the DMS, while that due to the latter state induces electron states with increased spatial distribution. Tight-binding theory is again used to describe the observed energy levels and the interactions between electron states induced by the magnetic elds due to separated vortices in the multivortex state.

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Dissertations / Theses on the topic 'Electronic semiconductor'

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