Dissertations / Theses: 'Semiconductor doping'

1

Liu, Jia. "Optical spectroscopic study of GaAs with dilute nitrogen doping /." View Abstract or Full-Text, 2002. http://library.ust.hk/cgi/db/thesis.pl?PHYS%202002%20LIU.

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2

OLBRIGHT, GREGORY RICHARD. "FEMTOSECOND DYNAMICS AND NONLINEAR EFFECTS OF ELECTRON-HOLE PLASMA IN SEMICONDUCTOR DOPED GLASSES." Diss., The University of Arizona, 1987. http://hdl.handle.net/10150/184091.

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The following is a comprehensive study of transient and steady-state nonlinear optical properties of semiconductor microcrystals embedded in a glass matrix (semiconductor doped glass). Transient thermal effects which give rise to longitudinal excitation discontinuities (i.e., kinks) that arise from partial sample switching in increasing absorption optical bistability are observed in a doped glass. The transient thermal effects occur on time scales of a few hundred milliseconds. Femtosecond and nanosecond laser pulses are employed to measure time-resolved and steady-state transmission and differential transmission spectra. The measured spectra reveal several beautiful effects which are attributed to the many-particle effects of electron-hole plasma. The spectra reveal: bandgap renormalization, broadening of the tail states and screening of the continuum states, state filling (spectral hole burning), thermalization of nonthermal carrier population distributions, band filling due to carrier relaxation of the thermal and nonthermal distributions, direct electron-hole recombination and long lived (>>100 ps) tail states which are attributed to electron trapping. Absorption edge dynamics discussed in this dissertation span 15 orders of magnitude.

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3

Archer, Paul I. "Building on the hot-injection architecture : giving worth to alternative nanocrystal syntheses /." Thesis, Connect to this title online; UW restricted, 2007. http://hdl.handle.net/1773/8520.

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4

Randell, Heather Eve. "Applications of stress from boron doping and other challenges in silicon technology." [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0010292.

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5

Daniels-Hafer, Carrie Lynn. "Electrochemical tuning of charge transport at inorganic semiconductor doped conjugated polymer interfaces through manipulation of electrochemical potential /." view abstract or download file of text, 2004.

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Thesis (Ph. D.)--University of Oregon, 2004.
Typescript. Includes vita and abstract. Includes bibliographical references (leaves 185-196). Also available for download via the World Wide Web; free to University of Oregon users.

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6

Los, Andrei. "Influence of carrier freeze-out on SiC Schottky junction admittance." Diss., Mississippi State : Mississippi State University, 2001. http://library.msstate.edu/etd/show.asp?etd=etd-03272001-120540.

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7

Leong, Hank W. H. "Investigation of dopant profiles from capacitance-voltage measurements on Schottky diodes." Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/29997.

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Measurement of the differential capacitance (C) of a Schottky diode as a function of voltage (V) is widely used to probe dopant profiles in semiconductors. However, the theory of the dopant profiling method is based on an approximation, and does not work well when the dopant concentration changes rapidly with distance. The region beyond the maximum of an implanted Gaussian profile is of particular interest in connection with ingot qualification tests for GaAs, and it is just there that the problem is the most serious. In this thesis, an investigation was made by numerical simulation on problems associated with the profiling method. Programs were written to calculate the differential capacitance-voltage relation for GaAs Schottky diodes with and without deep energy levels, and with a specified dopant distribution. The programs predict what the approximation method would indicate for the dopant profiles according to a set of canonical equations used in the profiling method. The predicted and the specified dopant profiles were then compared. Mainly ion-implanted dopant profiles in semiconductors were studied although doped epitaxial layers were also considered. For ion-implanted GaAs, the predicted dopant profiles were found to be about 10% lower near the peak region than the true dopant profiles, and the predicted profiles were confirmed to be too high in the tail region. For doped epitaxial layers, the predicted profile was found, in some cases, to give good estimates for the dopant concentrations on the high and low sides of the true step profile, but in some others, the predicted profiles were found to be totally misleading. For GaAs with deep levels, a method of calculating the differential capacitance was developed to take into account the fact that the deep levels do not respond to the 1 MHz a.c. signal normally used in the C(V) measurements. It is believed to simulate the experimental C(V) measurements more realistically. The tail sections of the predicted profiles were found to increase with the concentration of background shallow donor atoms in the deep-level-free semiconductor before ion-implantation, and with the number of impurity atoms which are channelled or diffused to the region during or after ion-implantation. This implies that although the profiling method is erroneous in the tail section, it can nevertheless be used on a comparative basis to indicate the level of background shallow dopant concentration, and the degree of channelling or diffusion. The effects of the substrate parameters in liquid encapsulated Czochralski (LEC) GaAs, which include the concentrations of EL2, net shallow acceptors, and sometimes Cr, have been investigated on the predicted dopant profiles for ion-implanted samples. Increases in Cr and net shallow acceptor concentrations were found to increase the steepness of the predicted dopant profile, while an increase in EL2 concentration has little effect. A method of estimating dopant activation efficiency in GaAs has been proposed. This method uses the author's second program to avoid underestimations of the activation efficiency in GaAs caused by the peak lowering in the predicted dopant profiles. The concept of Debye length in semi-insulating LEC GaAs was also discussed. The Debye length given by the standard formula for semiconductors with shallow donors and acceptors can become inapplicable when deep levels are present.
Applied Science, Faculty of
Electrical and Computer Engineering, Department of
Graduate

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8

Sung, Talun. "Doping diamond by forced diffusion /." free to MU campus, to others for purchase, 1996. http://wwwlib.umi.com/cr/mo/fullcit?p9720551.

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9

Chang, Ruey-dar. "Physics and modeling of dopant diffusion for advanced device applications /." Digital version accessible at:, 1998. http://wwwlib.umi.com/cr/utexas/main.

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10

Myers, Joseph Kenneth. "Inverse doping profile analysis for semiconductor quality control." Diss., Wichita State University, 2009. http://hdl.handle.net/10057/2556.

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Inverse doping pro le problems are linked to inverse conductivity problems under the assumptions of zero space charge and low injection. Unipolar inverse conductivity problems are analyzed theoretically via three uniqueness proofs, the rst of which has been published as a paper in Inverse Problems [34]. Also, optimized numerical methods are developed for solving the unipolar direct conductivity problem with a piecewise constant conductivity coe cient. Finally, the unipolar inverse conductivity problem is solved for inclusions de ned by as many as 9 parameters, or by as many as 120 parameters when an initial guess for each parameter is known with less than 10% error. Our free boundary identi cation algorithm produces a sequence of improved approximations in a way that provides both regularization and accelerated convergence towards the solution.
Thesis (Ph.D.)--Wichita State University, College of Liberal Arts and Sciences, Dept. of Mathematics and Statistics

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11

Hearne, M. T. "Diffusion models for the doping of semiconductor crystals." Thesis, University of Nottingham, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384711.

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12

West, Matthew K. "Diffusion of sulfur into natural diamond : characterization and applications in radiation detection /." free to MU campus, to others for purchase, 1999. http://wwwlib.umi.com/cr/mo/fullcit?p9964011.

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13

Cai, Xingmin. "Growth, doping and nanostructures of gallium nitride." Click to view the E-thesis via HKUTO, 2005. http://sunzi.lib.hku.hk/hkuto/record/B35806394.

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Cai, Xingmin, and 蔡興民. "Growth, doping and nanostructures of gallium nitride." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2005. http://hub.hku.hk/bib/B35806394.

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15

Erwin. "Electron eigenvalues and eigenfunctions for a nanochannel with a finite rectangular barrier." Virtual Press, 1994. http://liblink.bsu.edu/uhtbin/catkey/917032.

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Electron scattering by a single or multiple impurities affects the quantizaton of conductance of a semiconductor nanochannel. The theoretical model of electron transport in a hardwall nanostructure with an impurity requires an analysis of the electronic transverse energy levels, eigenfunctions and hopping integrals resulting from cross channel or transverse confinement. Theoretical equations for the electronic transverse energy levels, wavefunctions and hopping integrals in the case of a repulsive, finite strength rectangular barrier arbitrarily positioned in the nanochannel are presented. The effects of size, strength and location of the impurity are discussed.In order to find the electronic transverse energy levels, wavefunctions and hopping integrals, two FORTRAN computer programs were developed. The first, called Program Data Input, writes the computational parameters to a data file. The second, Program Single Impurity, uses this data file in performing the calculations of the electronic transverse energy levels, eigenfunctions and hopping integrals.
Department of Physics and Astronomy

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16

Thorley, Antony M. "Infrared characterisation of semiconductors." Thesis, University of St Andrews, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.278212.

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17

Brenner, Kevin A. "Benchmarking and chemical doping techniques for nanoscale graphene interconnects." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/47581.

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The interconnect fabric that provides electrical connectivity to active devices is an essential component to modern semiconductor chips. As the dimensions of these devices are scaled to improve performance and keep pace with Moore's Law, the local Cu interconnects must scale in parallel. Intrinsic material properties of Cu result in spiking electrical resistivity with scaling and present a looming bottleneck to chip performance. In this thesis, we introduce graphene as a replacement material to Cu interconnects in support of future chip scaling. In particular we focus on experimentally establishing fundamental mechanisms of chemically doping graphene via the basal plane and edge passivation, with broad contributions that extend beyond the focus of local interconnects.

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18

Cholan, Hemavathy. "Deep level transient spectroscopy of magnesium doped indium phosphide /." Full text open access at:, 1987. http://content.ohsu.edu/u?/etd,154.

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19

Zeroual, Boudjemaa. "Ion bombardment induced damage and annealing in Si." Thesis, University of Salford, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.258251.

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20

Buzzo, Marco. "Dopant imaging and profiling of wide bandgap semiconductor devices /." Konstanz : Hartung-Gorre, 2007. http://www.loc.gov/catdir/toc/fy0715/2007427206.html.

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21

Da, Cunha Carlo Requiao. "Processing and characterization of contacts on MBE-grown gallium nitride." Morgantown, W. Va. : [West Virginia University Libraries], 2001. http://etd.wvu.edu/templates/showETD.cfm?recnum=1837.

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Thesis (M.S.)--West Virginia University, 2001.
Title from document title page. Document formatted into pages; contains viii, 139 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 107-108).

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22

Geburt, Sebastian [Verfasser]. "Lasing and ion beam doping of semiconductor nanowires / Sebastian Geburt." Jena : Thüringer Universitäts- und Landesbibliothek Jena, 2013. http://d-nb.info/1034073818/34.

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23

Feng, Guofu. "Optical studies of ion-bombarded gallium arsenide." Diss., Virginia Polytechnic Institute and State University, 1989. http://hdl.handle.net/10919/54357.

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The present work studies the disorder in ion-implanted and ion-etched GaAs semiconductors. The primary targets in this study consist of two types of systems:45-keV Be⁺-implanted GaAs and low-energy Ar⁺-etched GaAs. Electronic and lattice structural disorder in these systems are investigated by means of optical reflectivity measurements and Raman-scattering techniques. Visible-ultraviolet reflectivity measurements have identified finite-size effects on the interband electronic excitations in microcrystalline GaAs (μ-GaAs), which is known from previous work to exist in Be⁺-implanted disordered GaAs. The optical properties of μ-GaAs differ appreciably from those of the bulk crystal, the difference increasing with L⁻¹, the inverse of the characteristic size of the microcrystals. The linewidths of the prominent interband features E₁, E₁+∆₁, and E₂ increase linearly and rapidly with inverse microcrystal size: Γ_μ = Γ₀ + AL⁻¹, where Γ₀ (Γ_μ) is the linewidth in the bulk crystal (μ-GaAs), and A is a constant. A simple theory is proposed which semi-quantitatively accounts for the observed size effects. Small microcrystal size implies a short time for an excited carrier to reach, and to be scattered by, the microcrystal boundary, thus limiting the excited-state lifetime and broadening the excited-state energy. An alternative uncertainty-principle argument is also given in terms of the confinement-induced k-space broadening of electron states. The near-surface structural disorder in Ar⁺-etched GaAs has been investigated using a combination of Raman scattering and optical reflectivity measurements. The longitudinal optical (LO) Raman mode in the ion-damaged medium preserves its crystalline lineshape, indicating that the crystalline long-range order is retained in the disordered structure. The structural damage is depth-profiled with LO Raman intensity measurements together with wet chemical etching. A graded damage model proposed in the work well explains the observed LO intensity in the ion-damaged, chemical-etched GaAs. The reflectivity measurements qualitatively support the Raman scattering findings. In addition, the reflectivity spectrum exhibits a red-shift of the peaks associated with the interband electronic transitions. Such a peak shift is likely to arise from the electron-defect interaction in the disordered surface medium.
Ph. D.

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24

Engel, Jesse Hart. "Size-Dependent Optoelectronic Properties and Controlled Doping of Semiconductor Quantum Dots." Thesis, University of California, Berkeley, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3616442.

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Given a rapidly developing world, the need exists for inexpensive renewable energy alternatives to help avoid drastic climate change. Photovoltaics have the potential to fill the energy needs of the future, but significant cost decreases are necessary for widespread adoption. Semiconductor nanocrystals, also known as quantum dots, are a nascent technology with long term potential to enable inexpensive and high efficiency photovoltaics. When deposited as a film, quantum dots form unique nanocomposites whose electronic and optical properties can be broadly tuned through manipulation of their individual constituents.

The contents of this thesis explore methods to understand and optimize the optoelectronic properties of PbSe quantum dot films for use in photovoltaic applications. Systematic optimization of photovoltaic performance is demonstrated as a function of nanocrystal size, establishing the potential for utilizing extreme quantum confinement to improve device energetics and alignment. Detailed investigations of the mechanisms of electrical transport are performed, revealing that electronic coupling in quantum dot films is significantly less than often assumed based on optical shifts. A method is proposed to employ extended regions of built-in electrical field, through controlled doping, to sidestep issues of poor transport. To this end, treatments with chemical redox agents are found to effect profound and reversible doping within nanocrystal films, sufficient to enable their use as chemical sensors, but lacking the precision required for optoelectronic applications. Finally, a novel doping method employing "redox buffers" is presented to enact precise, stable, and reversible charge-transfer doping in porous semiconductor films. An example of oxidatively doping PbSe quantum dot thin films is presented, and the future potential for redox buffers in photovoltaic applications is examined.

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25

Cole, Eric D. "On the feasibility and application of optical p to n inversion." Thesis, Virginia Tech, 1985. http://hdl.handle.net/10919/45719.

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The feasibility of achieving carrier inversion of a properly doped crystal via optical excitation is studied. This process involves a host substrate doped with deep donors for n-type light characteristic and compensated by a shallow acceptor for p-type characteristic in the dark. This substrate is analyzed using well-known semiconductor equations. In addition conditions which must exist for carrier inversion are also specified. The solutions found are applied to a realistic set of dopants for illustrative purposes as well as indication of feasibility range. This inversion technique may possibly be used to generate bipolar junctions and thus devices. Other forms of photoconductivity are also qualitatively considered to supplement and extend the range of the inversion techniques applications. The processing of circuits using the developed concept offers possible interesting and useful advantages over existing techniques. The motivation for further research thus becomes obvious and is indeed the purpose of the thesis.
Master of Science

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26

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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27

Evason, Andrew Frank. "Focused ion beams and their applications to the tailored doping of gallium arsenide MESFETS." Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.278227.

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28

Yang, Shu-Chun. "High pressure optical studies in conjugated polymers /." free to MU campus, to others for purchase, 1999. http://wwwlib.umi.com/cr/mo/fullcit?p9946318.

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29

彭澤厚 and Chak-hau Pang. "A study of Mg doping in GaN during molecular beam epitaxy." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2001. http://hub.hku.hk/bib/B31226619.

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30

Pang, Chak-hau. "A study of Mg doping in GaN during molecular beam epitaxy /." Hong Kong : University of Hong Kong, 2001. http://sunzi.lib.hku.hk/hkuto/record.jsp?B25059075.

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31

Luo, Ming. "Transition-metal ions in II-VI semiconductors ZnSe and ZnTe /." Morgantown, W. Va. : [West Virginia University Libraries], 2006. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=4630.

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Thesis (Ph. D.)--West Virginia University, 2006.
Title from document title page. Document formatted into pages; contains xiv, 141 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 135-141).

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32

Jadwisieńczak, Wojciech M. "The luminescence properties of the wide bandgap nitrides doped with rare earth ions and gallium nitride doped with conventional isoelectronic impurities." Ohio : Ohio University, 2001. http://www.ohiolink.edu/etd/view.cgi?ohiou1179158888.

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33

Pyke, Daniel James. "Hydrogen evolution and transport in semiconductors." Phd thesis, Canberra, ACT : The Australian National University, 2014. http://hdl.handle.net/1885/125142.

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Silicon-on-insulator structures are used for the fabrication of integrated electronic circuits, photonic devices and structures, and micro-electro-mechanical systems. The most common fabrication method for SOI is a hydrogen-induced cleavage technique in which ion-implanted hydrogen is employed to initiate and propagate cracks in a plane parallel to the silicon surface. Considerable research effort has been devoted to understanding this cleavage technique in (100) silicon but several fundamental issues remain unclear, including the role of stress on hydrogen platelet alignment. In addition, there is keen interest in extending the technique to other silicon orientations (i.e. (110) and (111)) and semiconductor materials (e.g. Ge). The intrinsic behaviour of hydrogen ion-implanted into Ge and Si was examined by ion beam analysis, optical profilometry and microscopy, to establish the influence of lattice damage and hydrogen evolution. In particular, hydrogen-induced blistering and crater formation under thermal annealing from T=300-650 degrees Celsius was studied to determine the activation energies in Ge and Si in several crystalline orientations. Similar techniques were employed as the influence of extrinsic applied stresses upon hydrogen's evolution within Si was studied, by mechanical stress application onto Si(100). XTEM was used to study the defect evolution related to the hydrogen and ion-implantation damage under anneals applied to samples under stress, in addition to samples produced in different stress conditions. Blistering rate and areal density was seen to follow logistic sigmoidal functions in all materials. Constant activation energies were measured for all Si samples under selected implantation conditions, but multiple activation energies were found in each Ge sample when the conditions were varied. Si(100) & Si(111) both blistered readily for all temperatures, Si(110) required higher H fluence and Ge showed inconsistent behaviour at different implantation conditions. Blister crater depth and roughness may be closer linked to local H concentration rather than total implantation fluence. High level doping of Si does not significantly change the dynamics of H blister formation, with potentially exploitable benefits for SOI production. Stress induced by ion implantation in Si and Ge is tensile, relaxes somewhat with thermal annealing, in the order of <1 MPa. Both 50 and 375um Si wafers behave similarly when implanted with H. Tensile stress applied to H-implanted thick Si(100) influenced hydrogen defect alignment within the lattice, shifting complexes to [110] and [100] planes following annealing. In ULTRATHIN Si, application of tensile stress may relatively diminish and compressive stress enhance diffusion of H, although any applied stress during implantation is seen to decrease H concentration. Applied stresses above 400 MPa cause the height of hydrogen surface blisters to decrease and density to increase. Blisters formed during annealing are not permanently decorated with nor contain hydrogen, whether under applied stress or not. Orientations of detectable defects are not strongly affected by application of stress, however concentrations are seen to decrease at high stress. The location of the ion-cut inducing defect does not appear to correspond to long term measurements of H or implantation damage, and may be even shallower, but this cannot be unambiguously confirmed.

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34

Monteiro, Pedro Manuel da Silva. "A close study of a ferromagnetic semiconductor : doping effects in EuO thin films." Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.709424.

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35

Luo, Hongfu. "Understanding and controlling defects in quantum confined semiconductor systems." Diss., Kansas State University, 2016. http://hdl.handle.net/2097/34520.

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Doctor of Philosophy
Department of Chemistry
Viktor Chikan
Semiconducting nanoparticles have emerged in the past few decades as an interesting material with great potential in various interdisciplinary applications such as light-emitting devices, solar cells and field-effect transistors, mostly notably for their size-dependent electronic structure and properties. Manipulation of their electronic-optical characters through defects control is one of the most important approaches towards realization of these applications. This thesis focuses on understanding the role of defects, including their impact on carrier density and conductivity at both room and elevated temperature, their impact on growth kinetics of colloidal nanoparticles and new opportunities for dopant control. To achieve these goals, colloidal CdSe quantum dots are doped with gallium atoms and important changes in electronic and optical properties of the material are reported, which shows a significant impact on the growth kinetics of quantum dots, and reveals clues about the mechanism of the gallium dopant incorporation into the CdSe. It is shown that the gallium doping significantly impacts the conductivity of CdSe thin film made of the quantum dots as well as the photoluminescence and chemical reactivity of the quantum dots, in agreement with the expected n-type character. P3HT/CdSe hybrid cells are constructed with Ga-, In- and Sn-doped CdSe QDs, demonstrating high conductivity and stronger electronic coupling which leads to enhanced charge separation and transport efficiency, both essential for hybrid inorganic-organic solar cells. This work also demonstrates a novel heating method that can drastically improve size distribution control of colloidal nanoparticle synthesis. Sub-2-nm ultra-small CdSe QDs are prepared with the induction (magnetic) heating and show excellent agreement of its emission profile compared with natural sunlight. The impact of extreme high heating rate on the development of more accurate nucleation and growth theories are also discussed. Finally, this study also investigates the stabilization of charges from intrinsic defects by looking for altered blinking behaviors of CdSe nanorods (NRs) under different polar environments. TMOS-PTMOS gradient films are prepared with infusion withdrawal dip-coating technique. Although no significant differences are observed of the fluorescence statistics of these NRs, permanent bleaching induced by exciting laser light is discovered, which significantly lowers raw blinking spot count and increases the “off” time of these fluorophores.

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Woodard, Eric M. "Low temperature dopant activation for applications in thin film silicon devices /." Link to online version, 2006. https://ritdml.rit.edu/dspace/handle/1850/1831.

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Farhoudi, Mohammad Mehdi. "Studies of structures, transport and magnetic properties of doped novel three-dimensional perovskite compounds." Institute for Superconducting and Electronic Materials - Faculty of Engineering, 2009. http://ro.uow.edu.au/theses/3047.

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Perovskite oxide compounds have generated a great amount of interest over the past twenty years, as they exhibit exotic magnetic, electric, and magnetoelectric properties, which, apart from their intrinsic interest, would have a wide range of applications in industry, with special utilization in the engineering of data storage devices.Starting with a general definition of the perovskite structure of ABO3 materials, the magnetic and transport properties of cobalt and manganese based compounds are reviewed. The objective of this thesis is focused on the investigation of the structures, and the magnetic and transport properties of some typical cobalt or manganese based three-dimensional perovskite compounds doped with various elements.Polycrystalline samples of RE1-xSrxCoO3 (RE = Gd, Nd, Ho, Y, and Dy), REMnxCo1-xO3 (RE = Gd and Ho), and La0.33Sr0.66Fe1-xCrxO3 were fabricated and characterized in detail using X-ray diffraction, Rietveld structural refinement, magnetic and transport measurements, X-ray absorption near-edge (XANES) spectroscopy, and far-infrared (FIR) spectroscopy.Perovskite GdCo1-xMnxO3 (x = 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8) compounds were prepared by solid-state reaction. Structures were characterized using X-ray diffraction and the Rietveld refinement method. The compounds crystallized in the orthorhombic structure with Plmn space group. Crystal lattice parameters constants decreased with increasing Mn doping level. DC magnetization and ac susceptibility were studied over a wide temperature range and different frequencies. A typical spin glass state was observed in all samples around the same temperature of 122 K, where the compounds changed from the paramagnetic to the ferromagnetic state. For x = 0.5, secondary transitions were observed both in dc and in ac measurements, which were independent of the frequency, but depended on the doping level. The valences of Co and Mn were estimated with possible spin states.The structures, magnetism, giant magnetoresistance, and spin and valence states of Co ions were investigated in perovskite Gd1-xSrxCoO3 (x = 0-0.5) compounds synthesized by a solid state reaction method. Results showed that all the samples are ferromagnetic around 150 K, and the magnetization and coercive field increase with the Sr doping level. A spin glass state was observed. Furthermore, the resistivity drops systematically with x. Giant magnetoresistance of over 60% was observed for the Gd0.5Sr0.5CoO3 sample. Spin state assessment indicates that the Co3+ and Co4+ ions are present in intermediate and high spin states.Polycrystalline perovskites compounds HoMn1-xCoxO3 (x = 0-0.8) were prepared by conventional solid-state reaction. Rietveld refinement indicated that, instead of a hexagonal structure with P63cm symmetry for HoMnO3, the compounds doped with Co crystallized in the GdFeO3-type orthorhombic structure containing distorted (Co/Mn)O6 octahedral. The dc magnetization was measured in fields up to 5 T over a wide temperature range from 350 K down to 5 K. It was found that the system gradually changed from paramagnetic for x = 0 to ferromagnetic with a Curie temperature, TC, of 90 K for x = 0.5, then to paramagnetic again for x = 0.8. X-ray absorption near-edge spectra (XANES) were collected to determine the valences of both Co and Mn ions. The results showed that Co and Mn were present mainly as mixed valences of Co2+ + Co3+, Mn4+ + Mn3+, Co3+ +Co4+, and Mn4+, depending on the value of x. When the XANES results were combined with Curie-Weiss fitting, it was found that both Mn4+ and Co3+ were present as high spin states for x > 0.2, whereas, Co4+ appeared in either intermediate or high spin states, closely corresponding to the lattice variations along the (010) direction. HoMn1-xCoxO3 (x = 0-0.8) compounds were also studied by far-infrared (FIR) spectroscopy in order to gain information on the infrared active phonon modes. The data indicated that phonon modes significantly changed with increasing cobalt doping level. Four main bands were assigned as external, torsional, bending, and stretching bands. The external vibration energy remained the same at 1190 cm-1 for Co doping with x < 0.5 and shifted to higher energy for x > 0 5. The torsional and bending bands exhibited splitting. The stretching band is at 600 cm-1 for all samples, but the bandwidth is reduced as Co doping is increased. The transmission spectrum of HoMn4/5Co1/5O3 was analyzed to obtain the spectrum of the optical density. The minimum number of oscillators to obtain a reliable fit is 5, using a sum of non-interacting harmonic oscillators.Cr doping effects on the crystal structures and magnetic properties for La1/3Sr2/3Fe1-xCrxO3 were studied in this work. It was observed that single phase samples with the cubic crystal structure can only form within a narrow solubility range. Magnetic measurements showed that the resulting compounds are magnetic insulators.

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Lindström, Anna. "Defects and Impurities in CdTe : An ab Initio Study." Doctoral thesis, Uppsala universitet, Institutionen för fysik och astronomi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-244964.

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In this thesis defects and impurities in CdTe have been studied with ab initio methods. CdTe is a II-VI semiconductor with many important applications such as γ- and X-ray detectors, solar cells and medical imaging. Even though CdTe has been studied for more than 70 years, some of its properties connected with defects and impurities, are still shrouded in mystery. Todays experimental techniques are highly developed and can provide rather detailed data, but require elaborate theoretical analysis. Here ab initio modelling comes into play and in particular density functional theory (DFT). When reviewing different theoretical studies of defects and impurities in CdTe, one finds a vast number of discrepancies between experiment and theory. Mismatches appear even between different theoretical studies. Although many problems, such as, for example, the semiconductor band gap underestimation or the spurious interaction between charged defects, are avoided by employing corrections or implementing new functionals, some of them still remain. Employing the hybrid functional HSE06, the following topics were studied in this thesis: - Te antisites: Experimental data predict the defect state to appear in the middle of the band gap, thus "pinning" the Fermi level. In contrast, our calculations show that Te antisite alone cannot be the reason for the Fermi level pinning, since it does not form a defect level in the middle of the band gap. Instead we propose that charge compensation between Te antisites in a (+2) state and Cd vacancies in a (-2) state explains the Fermi level pinning. - Cd vacancy: Electron paramagnetic resonance experiments clearly show the existence of a hole polaron for the (-1) charged vacancy. But DFT studies report a completely delocalised hole. In our studies, for the first time, this state was found in its proper geometrical configuration with a hole localisation stabilised by a Jahn-Teller distortion, thereby removing the discrepancy between experiment and theory. - Cd chalcogenides: Additionally, with particular focus on the hole localisation problem, the series of isovalent compounds (CdTe, CdSe and CdS) was studied to understand the mechanism of hole polaron formation. We explain the trend of the hole localisation in terms of Coulomb interaction, explicitly showing that the effect of electron correlation is negligible. - Cl-doped CdTe: The formation of a Cl - Cd vacancy complex explains the selfcompensation and selfpurification mechanism. We find Cl to annihilate the hole polaron. - Te antisite under deformation: In an attempt to tailor the energy position of the Te antisite defect level in the CdTe band gap, we studied CdTe under different deformations. It is shown that by a carefully chosen deformation the defect levels can be pushed closer to the valence and/or conduction band and hence the CdTe detector performance may be improved.

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39

Gong, Bin. "Surface reactions, hydride kinetics and in situ boron doping of silicon and germanium /." Digital version accessible at:, 1999. http://wwwlib.umi.com/cr/utexas/main.

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Herrbach-Euvrard, Julie. "Organic semiconductor p-doping : toward a better understanding of the doping mechanisms and integration of the p-doped layer in organic photodetectors." Thesis, Lille 1, 2017. http://www.theses.fr/2017LIL10072/document.

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Contrairement à l’électronique conventionnelle à base de silicium, l’électronique organique offre de nouvelles possibilités telles que la production sur grande surface et à faible bilan thermique, ou encore l’utilisation de substrats flexibles et transparents. Afin d’améliorer la conductivité des semi-conducteurs ainsi que le contact polymère-électrode métallique, le dopage en électrons et en trous doit être développé dans les matériaux organiques. Dans cette thèse, des techniques de caractérisation électrique (courant tension à température variable, capacité, spectroscopie d’admittance), optique (spectroscopie UV-visible et de photoluminescence) et matériau (RMN, MEB, MET) ont été utilisées pour analyser l’influence de la concentration en dopant Mo(tfd-COCF3)3 sur les propriétés électriques du polymère PBDTTT-c et améliorer notre compréhension du mécanisme mis en jeu dans le dopage. La couche dopée a été intégrée avec succès dans un photodétecteur organique en utilisant une technique de laminage afin de remplacer la couche habituellement utilisée de PEDOT:PSS, connue pour générer des problèmes de stabilité dans le dispositif. Enfin, la technique de laminage et le savoir acquis sur le dopage des semi-conducteurs organiques ont permis d’étudier l’impact du dopage non intentionnel par l’oxygène sur les performances des photodétecteurs organiques. Bien qu’il soit encore nécessaire de renforcer notre compréhension sur le dopage des semi-conducteurs organiques, améliorer la technique de dépôt par laminage et introduire la couche dopée dans divers dispositifs imprimés, les résultats présentés dans cette thèse sont prometteurs pour le développement de l’électronique organique
Organic electronics is a promising route for the next generation of electronic devices. With large area scalability, compatibility with flexible and semitransparent substrates, and low temperature processability, printed electronics offers an interesting alternative to conventional silicon-based electronics. On its way to achieve better performances, hole and electron doping needs to be developed to improve the material conductivity as well as the polymer-metal electrode contact. In this work, we have studied the electrical characteristics of the polymer PBDTTT-c upon addition of p-dopant Mo(tfd-COCF3)3. Complementary electrical (variable temperature current voltage, capacitance, admittance spectroscopy), optical (UV-visible absorption and photoluminescence spectroscopy) and material (NMR, SEM, TEM) characterization techniques have been used to analyze the impact of the doping concentration on the electrical properties of the polymer and improve our understanding of the doping mechanism involved. The doped layer was then successfully integrated in an organic photodetector using soft contact transfer lamination to replace the widely used PEDOT:PSS layer, known to be responsible for stability issues. Finally, both the lamination technique and the knowledge acquired on organic semiconductor doping were used to study the impact of unintentional oxygen doping on the organic photodetector performances.Although further works are necessary to complete our understanding of organic semiconductor doping, enhance the lamination processes and introduce doped layers in various solution printed devices, present results are promising for the improvement of organic electronic devices

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41

Banyai, William Charles. "Optical nonlinearities in semiconductor doped glass channel waveguides." Diss., The University of Arizona, 1988. http://hdl.handle.net/10150/184505.

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The nonlinear optical properties of a semiconductor-doped glass (SDG) channel waveguide were measured on a picosecond time-scale; namely, fluence-dependent changes in the absorption and the refractive index as well as the relaxation time of the nonlinearity. Slower, thermally-induced changes in the refractive index were also observed. The saturation of the changes in the absorption and the refractive index with increasing optical fluence is explained using a plasma model with bandfilling as the dominant mechanism. The fast relaxation time of the excited electron-hole plasma (20 ps) is explained using a surface-state recombination model. A figure of merit for a nonlinear directional coupler fabricated in a material with a saturable nonlinear refractive index is presented. The measured nonlinear change in the refractive index of the SDG saturates below the value required to effect fluence-dependent switching in a nonlinear directional coupler. Experiments with a channel-waveguide directional coupler support this prediction. However, absorption switching due to differential saturation of the absorption in the two arms of the directional coupler was observed.

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42

Ptak, Aaron J. "Growth kinetics and doping of gallium nitride grown by RF-plasma assisted molecular beam epitaxy." Morgantown, W. Va. : [West Virginia University Libraries], 2001. http://etd.wvu.edu/templates/showETD.cfm?recnum=1895.

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Thesis (Ph. D.)--West Virginia University, 2001.
Title from document title page. Document formatted into pages; contains xvii, 161 p. : ill. Includes abstract. Includes bibliographical references (p. 154-161).

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43

Goh, Kuan Eng Johnson Physics Faculty of Science UNSW. "Encapsulation of Si:P devices fabricated by scanning tunnelling microscopy." Awarded by:University of New South Wales. School of Physics, 2006. http://handle.unsw.edu.au/1959.4/27022.

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This thesis demonstrates the effective use of low temperature molecular beam epitaxy to encapsulate planar Si:P (phosphorus-in-silicon) devices lithographically patterned by scanning tunnelling microscopy (STM) without significant redistribution of the dopants. To achieve this goal, low temperature magnetotransport is used in combination with STM, Auger electron spectroscopy and secondary ion-mass spectrometry to analyse Si:P ??-doped samples fabricated under different doping and growth conditions. An important aspect of this project is the use of large 1 ?? 1 cm2 Si(001) samples which are about five times larger than standard STM samples. The larger sample size is necessary for post-STM fabrication lithography processes in a cleanroom but presents problems for preparing atomically clean surfaces. The ability to prepare clean and atomically flat Si(001) surfaces for STM lithography on such 1 ?? 1 cm2 samples is demonstrated, and it is shown that Si:P ??-doped layers fabricated on these surfaces exhibit complete electrical activation. Two dopant sources (gaseous PH3 and solid GaP source) were investigated to assess their compatibility with STM-lithography on the H:Si(001) surface. The findings show that while the PH3 and GaP sources result in near identical electrical qualities, only PH3 molecules are compatible with H-resist based lithography for controlled nano-scale doping. For achieving complete activation of the P dopants, it is shown that an anneal to ??? 350 ???C to incorporate P atoms into the Si surface prior to encapsulation is critical. While it is known that the presence of H during growth degrades the quality of Si epitaxy, investigations in this thesis indicate that it has no significant effect on dopant activation. Systematic studies performed to assess the impact of growth temperature recommend an encapsulation temperature of 250 ???C for achieving optimal electrical qualities with minimal dopant segregation. In addition, it is shown that rapid thermal anneals (RTAs) at temperatures < 700 ???C provide only marginal improvement in the electrical quality of Si:P ??-doped samples encapsulated at 250 ???C, while RTA temperatures > 700 ???C should be avoided due to the high probability of dopant redistribution. To elucidate the nature of 2D transport in Si:P ??-doped devices, a detailed analysis of the low temperature magnetotransport for Si:P ??-doped layers with doping densities in the range ??? 0.2 ??? 2 ?? 1014 cm???2 was carried out. Using conventional 2D theories for disordered systems, both weak localisation (WL) and electron-electron interactions (EEI) are shown to contribute almost equal corrections to the 2D conductivity. In particular, it is found that EEI can introduce a significant correction in the Hall coefficient RH (hence Hall density) especially in the low density/temperature regime and the need to correct for this when using the Hall density to estimate the activated electron density is highlighted. While the electronic mean free path in such highly doped ??-layers is typically < 10 nm making ballistic transport in these devices difficult to observe, the phase coherence length can extend to almost 200 nm at about 0.3???0.5 K for doping densities of ??? 1 ??? 2 ?? 1014 cm???2. Finally, the optimised encapsulation strategy developed in this thesis is applied to a 2D square device fabricated by STM. The device exhibits Ohmic conductivity with complete dopant activation. An analysis of its low temperature magnetotransport shows that the device behaves similarly to a Si:P ??-doped layer encapsulated under similar conditions, thus highlighting that the STM patterning process had no adverse effect on device quality.

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Rablău, Corneliu Ioan. "Photoluminescence and optical absorption spectroscopy of infrared materials Cr²+:ZnSe and ZnGeP₂." Morgantown, W. Va. : [West Virginia University Libraries], 1999. http://etd.wvu.edu/templates/showETD.cfm?recnum=1124.

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Thesis (Ph. D.)--West Virginia University, 1999.
Title from document title page. Document formatted into pages; contains xv, 200 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 194-200).

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45

Yang, Yaxiang. "FP-LMTO modeling of ZnSe and ZnMgSe alloy." Morgantown, W. Va. : [West Virginia University Libraries], 2001. http://etd.wvu.edu/templates/showETD.cfm?recnum=2247.

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Thesis (Ph. D.)--West Virginia University, 2001.
Title from document title page. Document formatted into pages; contains viii, 113 p. : ill. (some col.). Includes abstract. Includes bibliographical references.

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46

Li, Kaile. "Defects at surface and interface of crystals : theoretical and x-ray scattering analysis /." free to MU campus, to others for purchase, 2002. http://wwwlib.umi.com/cr/mo/fullcit?p3074422.

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47

Sazio, Pier-John Anthony. "In situ fabrication of 3-D patterned semiconductor structures using FIB doping during MBE growth." Thesis, University of Cambridge, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624877.

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48

Khoshsirat, Nima. "Investigation of the doping effect on Cu2ZnSnS4 thin film properties for photovoltaic applications." Thesis, Queensland University of Technology, 2019. https://eprints.qut.edu.au/130700/1/Nima_Khoshsirat_Thesis.pdf.

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The aim of this research is to increase the efficiency of thin film solar cells made by Copper, Zinc, Tin and Sulfur (CZTS). By including a small amount of chromium in the absorber layer has improved dramatically the light absorption of CZTS films in the infrared region, making use of a portion of solar spectrum never accessed before. This study revealed that a 4% Cr concentration produced a 90% increase in the efficiency, due to a double step absorption of low energy photons. These findings open the way to highly efficient CZTS solar cells.

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49

Yang, Jing. "P-n junction dopant profiling using scanning capacitance microscopy /." [St. Lucia, Qld.], 2004. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe18333.pdf.

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Hong, Yang David. "Modelling and inverse modelling of scanning capacitance microscopy for dopant profile extraction /." [St. Lucia, Qld.], 2005. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe19105.pdf.

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Dissertations / Theses on the topic 'Semiconductor doping'

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