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Tesi sul tema "Semiconductors"
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1
Hong, Sang Jeen. "Real-time malfunction diagnosis and prognosis of reactive ion etching using neural networks". Diss., Available online, Georgia Institute of Technology, 2004:, 2003. http://etd.gatech.edu/theses/available/etd-04082004-180227/unrestricted/hong%5Fsang%5Fj%5F200312%5Fphd.pdf.
Testo completo
2
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.
Testo completo
3
Park, Seung-Han. "Excitonic optical nonlinearities in semiconductors and semiconductor microstructures". Diss., The University of Arizona, 1988. http://hdl.handle.net/10150/184551.
Testo completoAbstract (sommario):
This dissertation describes the study of excitonic optical nonlinearities in semiconductors and semiconductor microstructures. The main emphasis is placed on the evolution of optical nonlinearities as one goes from bulk to quantum-confined structures. Included are experimental studies of molecular-beam-epitaxially-grown bulk GaAs and ZnSe, GaAs/AlGaAs multiple-Quantum-Wells (MQW's), and finally, quantum-confined CdSe-doped glasses. The microscopic origins and magnitudes of the optical nonlinearities of bulk GaAs and ZnSe were investigated and the exciton recovery time in ZnSe was measured. A comparison with a plasma theory indicates that in GaAs, band filling and screening of the continuum-state Coulomb enhancement are the most efficient mechanisms, while in ZnSe, exciton screening and broadening are the dominating mechanism for the nonlinearity. The maximum nonlinear index per excited electron-hole pair of ZnSe at room temperature is comparable to that of bulk GaAs and the exciton recovery times are of the order of 100 ps or less. A systematic study of the dependence of the optical nonlinearities on quantum well thickness for GaAs/AlGaAs MQWs and the results of nonlinear optical switching and gain in a 58 A GaAs/AlGaAs MQW are reported and discussed. The maximum change in the refractive index is greatest for the MQWs with the smallest well size and decreases with increasing well size, reaching a minimum for bulk GaAs. The maximum index change per photoexcited carrier increases by a factor of 3 as the well size decreases from bulk to 76 A MQW. A differential energy gain of 0.2 and the contrast of 4 are measured for a 58 MQW using 3 ns laser pulses. The linear and nonlinear optical properties of CdSe semiconductor microcrystallites grown under different heat treatments in borosilicate glasses are investigated. Pump-probe spectroscopic techniques and interferometric techniques were employed to study size quantization effects in these microcrystallites (quantum dots). Nonlinear optical properties due to the transitions between quantum confined electron and hole states are reported for low temperature and room temperature. A relatively large homogeneous linewidth is observed. Single beam saturation experiments for quantum confined samples were performed to study the optical nonlinearities as a function of microcrystallite size. Results indicate that the saturation intensity is larger for smaller size quantum dots.
4
Mardikar, Yogesh Mukesh. "Energy analysis, diagnostics, and conservation in semiconductor manufacturing". Morgantown, W. Va. : [West Virginia University Libraries], 2004. https://etd.wvu.edu/etd/controller.jsp?moduleName=documentdata&jsp%5FetdId=3748.
Testo completoAbstract (sommario):
Thesis (M.S.)--West Virginia University, 2004.Title from document title page. Document formatted into pages; contains viii, 152 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 106-108).
5
Ramamurthi, Vikram. "Analysis of production control methods for semiconductor research and development fabs using simulation /". Link to online version, 2004. https://ritdml.rit.edu/dspace/handle/1850/938.
Testo completo
6
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.
Testo completo
7
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.
Testo completo
8
Calhoun, Kenneth Harold. "Thin film compound semiconductor devices for photonic interconnects". Diss., Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/15478.
Testo completo
9
Ma, Cliff Liewei. "Modeling of bipolar power semiconductor devices /". Thesis, Connect to this title online; UW restricted, 1994. http://hdl.handle.net/1773/6046.
Testo completo
10
Peng, Harry W. "The effects of stress on gallium arsenide device characteristics". Thesis, University of British Columbia, 1988. http://hdl.handle.net/2429/28584.
Testo completoAbstract (sommario):
For VLSI applications, it is essential to have consistent device characteristics for devices fabricated on different fabrication runs, on different wafers, and especially across a single wafer. MESFETs fabricated on GaAs have been found to have an orientation dependence in their threshold voltage and other characteristics. For MESFETs with gate length less than 2 μm, changing the device orientation can so significantly alter the device characteristics that it must be considered during the transistor design stage. The causes for the orientation dependence in the device characteristics have been suggested to be the piezoelectric property of GaAs and stress in the substrate. Stress produced by the encapsulating dielectric film generates a polarization charge density in the substrate. If the magnitude of the polarization charge density is large enough to alter the channel doping profile, then the device characteristics are changed. In this thesis, the effects of stress on GaAs MESFET device characteristics were studied by modelling and experimental works.
In the modelling part, polarization charge densities under the gate of an encapsulated MESFET were calculated by using the so called distributed force model and the edge concentrated model. The distributed force model is a much better model because it describes more realistically the stress distribution in the film and in the substrate. It should provide a much more accurate calculation of the induced polarization charge density. The results show that the polarizarition charge densities calculated by the two models have similar distribution pattern, but the magnitudes are very different. With an identical set of conditions, a much larger polarization charge density is predicted by the edge concentrated model. In addition, the distributed force model distinguishes different films by a "hardness" value, based on their elastic property, whereas the edge concentrated model does not. A film with a larger "hardness" value is predicted to generate a larger polarization charge density. Two types of film were considered, SiO₂ and Si₃N₄. Using bulk film characteristics, the calculations showed that Si0₂ film is "harder" than Si₃N₄ film. If an equal built-in stress value is assumed, then a larger polarization charge density is predicted for Si0₂ than for Si₃N₄ encapsulated substrates.
In the experimental part, stress was applied to test devices by bending strips of GaAs wafers in a cantilever configuration. MESFETs tested were oriented in the [011] or the [011̅] direction. Both static stress and time-varying stress were applied. In the statics stress experiment, the changes in the barrier height and the C-V profile were measured. It was found that, with equal stress applied, Schottky barriers with a larger ideality factor showed a larger change in the barrier height. In the time-varying stress experiment, attempts were made to measure the effect of the polarization charge density on device characteristics by measuring changes in the drain-source current.Applied Science, Faculty of
Electrical and Computer Engineering, Department of
Graduate
11
Erwin. "Electron eigenvalues and eigenfunctions for a nanochannel with a finite rectangular barrier". Virtual Press, 1994. http://liblink.bsu.edu/uhtbin/catkey/917032.
Testo completoAbstract (sommario):
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
12
Mahadavan, Malina. "Analytical aspects of metal semiconductor barriers based on organic semiconductors". Thesis, University of Liverpool, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.490804.
Testo completoAbstract (sommario):
Over recent years, research into organic semiconductors has intensified considerably due to the increasing commercial viability of inexpensive, flexible, large area electronic applications. In particular, the introduction of a new generation of small molecule based organic semiconductors has increased the possibility of achieving high field effect mobilities. So far pentacene seems to be the most promising candidate since it yields field effect mobilities that are comparable to that of hydrogenated amorphous silicon (a-Si:H). Recently, a mobility larger than 1.2 cm2y-fs-l and an on/off ratio greater than 108 was reported for a thin film transistor (TFT) made with triisopropylsilyl pentacene (TIPSpentacene) as the active material. The solution processability of TIPS-pentacene is advantageous since solution-processed organic TFTs are needed to pave the way for low cost manufacturing approaches such as inkjet printing and roll-to-roll processing. One ofthe main potential applications for organic materials is in low cost radio frequency identification (RFID) tags operating at a frequency of 13.56MHz. The high frequency op~ration of RFID tags will be most demanding on the rectifying component of the circuit which can be based either on a TFT or a rectifying diode. This thesis is primarily concerned with analysing metal semiconductor barriers made with a variety of organic semiconductors such as highly regioregular poly(3-hexylthiophene) (p3HT), polytriarylamine (PTAA) (S 1105) and vacuum-deposited pentacene. The work includes a review of the various charge transport models proposed along with a discussion on the Meyer Neldel Rule (MNR) which is a commonly occurring phenomenon in organic semiconductors. A simple analytical model that demonstrates the empirical relationship between mobility and carrier density is also developed. This general dependency is formally known as the Universal Mobility Law (UML). The electrical characteristics of Schott)..)' junctions made between aluminium and various organic solids are investigated. Both P3HT and PTAA are highly disordered semiconductors whilst pentacene is a small molecule organic semiconductor akin to polycrystalline inorganic solids. The analysis of the pentacene vertical diode is thus extensively based on the model developed by Eccleston. The AI-PTAA Schott)..)' diode is found to not only yield a high rectification ratio but also an extremely low off current which suggests that the device is most suitable for low current circuit operations. In contrast, diodes based on P3HT and pentacene demonstrate much weaker rectifYing properties. Nevertheless, in these diodes, the non-saturation of the reverse currents allows the dopant densities ofthe materials to be determined. The new current density expression developed for organic based Schottk.')' diodes allows the characteristic temperature of the exponential distribution of intrinsic carriers (To) and states (Te) to be determined directly from the forward current density voltage characteristic. The Meyer Neldel energy representing the exponential density of states (DOS) is then obtained using the value of Te• In general, the !\tIN energy estimated from the exponential current regime ofthe diodes range between 30 meV and 35 meV. Special attention is given to the saturation current region of the diodes as relatively high currents are needed to satisfY the demands ofRFID related circuits. The saturation current of the as-synthesised P3HT diode was found to obey Ohm's law over the entire applied voltage range. In contrast, the PTAA and pentacene diodes demonstrate a transition from ohmic to space charge limited (SCL) conduction with increasing applied bias. The saturation current regime of these diodes is modelled using the new SCL current expression developed for disordered materials. The intrinsic value of Te determined for both diodes suggests the absence of dopant states at higher energies. The effects of changing the back metal/organic interface and further with doping with 2,3-dichloro-5,6-dicyano-I,4-benzoquinone (DDQ) on the saturation region ofAI-PTAA Schottk.')' diodes are also studied. Finally, the temperature variation of the current density voltage characteristics of assynthesised P3HT and PTAA Schottk.')' diodes are analysed. Below room temperature, the distinct fall in the forward exponential slope leads to much larger ideality factors 1/. This is attributed to the non-ideal behaviour of the Schottk.')' barrier interface with decreasing temperature. The anomalous rise in 1/ is attributed to a number of possibilities including the presence of extrinsic trapping states, carriers taking alternative routes to other potential barriers and the lack of validity of the flat quasi Fermi level approximation. Modelling the saturation current region of the PTAA diode with the new SCL current expression yields a self-consistent value of Te at relatively high temperatures. The steep decline in the Meyer Neldel energy observed at lower temperatures is mainly attributed to the formation of a potential barrier at the back metal/organic interface.
13
Halindintwali, Sylvain. "A study of hydrogenated nanocrystalline silicon thin films deposited by hot-wire chemical vapour deposition (HWCVD)". Thesis, University of the Western Cape, 2005. http://etd.uwc.ac.za/index.php?module=etd&.
Testo completoAbstract (sommario):
In this thesis, intrinsic hydrogenated nanocrystalline silicon thin films for solar cells application have been deposited by means of the hot &ndashwire chemical vapour deposition (HWCVD) technique and have been characterised for their performance. It is noticed that
hydrogenated nanocrystalline silicon is similar in some aspects (mainly optical) to its counterpart amorphous silicon actually used as the intrinsic layer in the photovoltaic industry. Substantial differences between the two materials have been found however in their respective structural and electronic properties.
We show that hydrogenated nanocrystalline silicon retains good absorption coefficients known for amorphous silicon in the visible region. The order improvement and a reduced content of the bonded hydrogen in the films are linked to their good stability. We argue that provided a moderate hydrogen dilution ratio in the monosilane gas and efficient process pressure in the deposition chamber, intrinsic hydrogenated nanocrystalline silicon with photosensitivity better than 102 and most importantly resistant to the Staebler Wronski effect (SWE) can be produced.
This work explores the optical, structural and electronic properties of this promising material whose study &ndash
samples have been exclusively produced in the HWCVD reactors based in the Solar Cells laboratory of the Physics department at the University of the Western Cape.
14
Modi, Nihar Triplett Gregory Edward. "Thermal management in GaAs/AlGaAs laser diode structures". Diss., Columbia, Mo. : University of Missouri--Columbia, 2007. http://hdl.handle.net/10355/6262.
Testo completoAbstract (sommario):
Title from PDF of title page (University of Missouri--Columbia, viewed on Feb. 16, 2010). The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Thesis supervisor: Dr. Gregory Triplett. Includes bibliographical references.
15
Johnson, William A. "What constitutes national security in the semiconductor industry? a look at the competing views surrounding DoD's support of semiconductuors /". Monterey, California : Naval Postgraduate School, 1990. http://handle.dtic.mil/100.2/ADA241699.
Testo completoAbstract (sommario):
Thesis (M.S. in Financial Management)--Naval Postgraduate School, December 1990.Thesis Advisor(s): Gates, William. Second Reader: Terasawa, Katsuaki. "December 1990." Description based on title screen as viewed on March 31, 2010. DTIC Identifier(s): Semiconductor Industry, Budgets, Department Of Defense, Theses. Author(s) subject terms: Semiconductors, National Security, Federal Economic Intervention. Includes bibliographical references (p. 69-71). Also available in print.
16
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.
Testo completoAbstract (sommario):
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.
17
Reig, Canyelles Marta. "Carbazole-Based Materials for Organic Thin-Film Transistors and Organic Light-Emitting Diodes". Doctoral thesis, Universitat de Barcelona, 2017. http://hdl.handle.net/10803/404560.
Testo completoAbstract (sommario):
This thesis deals with the preparation and characterization of novel organic semiconductors based on the carbazole heterocycle for electronic and optoelectronic applications, specifically to be studied as active layers in OTFTs and as emitting layers in OLEDs. Carbazole-based materials are recognised for their high thermal stability, high emission efficiencies and excellent hole-transporting properties associated to its electron-donating ability, which make of them promising candidates for OTFTs and OLEDs applications.
OLEDs have been studied extensively due to their promising applications in flat panel displays and solid-state lighting. However, further improvement of power efficiency and colour purity are still required to produce more efficient industrial devices. Thus, the first part of this thesis deals with the preparation of a series of carbazole-based blue emitters for their application as emitting layers in blue and in particular in deep-blue OLEDs. The extension of the π-conjugated carbazole system by preparing bicarbazole and tricarbazole derivatives afforded materials with the sought deep-blue emission properties in the solid state, which were modulated by the insertion of the ethynylene linker. OLED devices exhibited very low turn-on voltages and a maximum luminance as high as 1.4 x 104 cd m–2.
The second part of this thesis is focused on the development of new organic semiconductors with effective charge transport properties. In order to obtain new n-type or ambipolar materials, the hole-transporting behaviour of the electron-donating carbazole moiety was modified by the introduction of electron-withdrawing groups on its structure. As a first approach, the coupling of the carbazole heterocycle with the electron acceptor tris(2,4,6-trichlorophenyl)methyl radical (TTM) yielded ambipolar materials, whose charge-transporting properties were found to be dependent on the substitution patterns of the carbazole core. As a second approach, the introduction of the strong electron-withdrawing tricyanovinyl group on the carbazole core afforded a push-pull system with high electron affinity, resulting in materials with n-type or ambipolar behaviour as determined by TOF and OTFT measurements.
The last part of this thesis is focused on the preparation of a series of p-type carbazole related derivatives, in which the extension of the π-conjugated core was progressively varied in order to study its effect on the charge-transporting properties. Indolo[3,2-b]carbazole and triindole derivatives showed enhanced OTFT device performance with hole mobilities in the range of 10–3 to 0.1 cm2 V–1 s–1. In particular, N-trimethyltriindole exhibits a face-to-face molecular packing with π–π interactions, and an optimal perpendicular molecular disposition to the substrate surface as determined by XRD, that can be related to a more favourable charge transport in the OTFT devices. The introduction of long hexyl chains in the triindole core contributes with additional C–H···π interactions to those of π–π type between the triindole cores, enhancing the degree of molecular order in the thin films as reflected in the determined hole mobility, which was found to be the highest value of all the series with a value of 0.1 cm2 V–1 s–1.
The knowledge of the molecular packing and intermolecular interactions in the organic layers has been proved to be essential to rationalize the charge-transporting properties and it is shown here to be a useful tool to be considered on the design of new organic semiconductors.El desenvolupament de nous semiconductors orgànics amb capacitat de transport de càrrega presenta un gran interès per a la seva aplicació en transistors orgànics de capa prima (OTFTs), díodes emissors de llum orgànics (OLEDs) i cel·les solars orgàniques, entre d’altres. L’objectiu d’aquesta tesi és la preparació i caracterització de nous semiconductors orgànics basats en l’heterocicle carbazole i el seu estudi com a components en OTFTs i en OLEDs. En primer terme, aquesta tesi està centrada en la preparació de nous derivats del carbazole amb propietats luminescents en la zona del blau de l’espectre electromagnètic. En concret, es pretén modular les propietats òptiques del carbazole mitjançant l’extensió de la conjugació del seu nucli aromàtic per introducció de grups donadors d’electrons en la seva estructura, així com per la introducció del triple enllaç com a espaiador entre el nucli carbazole i els grups donadors d’electrons. L’estudi dels materials preparats com a capes emissores en OLEDs ha donat lloc a dispositius amb emissió a la zona del blau que han presentat una elevada luminància de fins a 1.4 x 104 cd m–2. La segona part de la tesi està enfocada en el desenvolupament de nous semiconductors orgànics basats en l’heterocicle carbazole i l’estudi de les seves propietats de transport de càrrega. Per tal de preparar nous semiconductors orgànics de tipus n o ambipolars, es pretén modificar les propietats de transport de forats del nucli carbazole mitjançant la introducció de grups atractors d’electrons en la seva estructura. Per una altra banda, s’ha preparat una sèrie de materials basats en el carbazole en què s’ha variat progressivament l’extensió del seu sistema conjugat, per tal d’obtenir derivats amb propietats de transport de forats efectives. Les propietats de transport de càrrega dels materials preparats s’han avaluat mitjançant la tècnica “time of flight” (TOF) i la preparació i mesura de OTFTs. S’han obtingut alts valors de mobilitat de forats de fins a 0.1 cm2 V–1 s–1 a partir de OTFTs basats en derivats del triindole. Els resultats obtinguts s’han correlacionat amb l’estructura molecular, el tipus d’empaquetament molecular, i amb el grau d’ordre i disposició de les molècules a les capes dels dispositius mitjançant estudis de difracció de raigs X i càlculs teòrics.
18
Zhao, Shen. "Propriétés optiques de nanorubans et boites quantiques de graphène". Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLN032/document.
Testo completoAbstract (sommario):
Ce manuscrit présente une étude expérimentale sur les propriétés optiques des nanorubans de graphène (acronyme anglais : GNRs) et des boites quantiques de graphène (acronyme anglais : GQDs) synthétisés par la chimie ascendante.Pour la partie sur les GNRs, les spectres d'absorption et de photoluminescence ainsi que les mesures de la durée de vie sur la dispersion impliquent la formation d'états excimères résultant de l'agrégation des GNRs. Au moyen de la microscopie confocale et de la microscopie à force atomique, nous observons l'émission de petits agrégats de GNRs confirmant leur capacité à émettre de la lumière à l'état solide. D'autre part, les caractérisations optiques des GNRs synthétisés sur une surface d’or présentent des caractéristiques de Raman remarquables, impliquant les propriétés vibrationnelles spécifiques des GNRs par rapport au graphène et aux nanotubes de carbone. La PL observée est spectralement large avec une énergie plus élevée que celle de la bande interdite des GNRs. Cela pourrait être lié aux défauts créés lors de la préparation de l'échantillon.Pour la partie sur les GQDs, les résultats de spectroscopie optique indiquent que les GQDs sont individualisées en dispersion plutôt que sous la forme d’agrégats. Ensuite, grâce à la microphotoluminescence, nous abordons directement les propriétés intrinsèques des GQDs uniques. Des mesures de corrélation de photons de second ordre révèlent que les GQDs présentent une émission de photons uniques avec une grande pureté. De plus, l'émission de GQD présente une bonne photo-stabilité avec une brillance élevée. Comme premier exemple de l'accordabilité optique des GQDs via le contrôle de la structure, nous observons que l'émission de GQDs fonctionalisés avec des atomes de chlore est décalée de près de 100 nm tout en maintenant une émission de photons uniquesThis manuscript presents an experimental study on the optical properties of graphene nanoribbons (GNRs) and graphene quantum dots (GQDs) synthesized by bottom-up chemistry.For the part on GNRs, the optical absorption and photoluminescence spectra as well as the life-time measurements on the dispersion of solution-mediated synthesized GNRs implies the formation of excimer states as a result of aggregation of GNRs. By means of confocal fluorescence microscopy and atomic force microscopy, we observe the emission of small GNR aggregates confirming the ability of GNRs to emit light in the solid state. On the other hand, the optical characterizations of on-surface synthesized GNRs shows remarkable Raman features, implying the distinct vibrational properties of GNRs compared to graphene and carbon nanotubes. The observed PL is spectrally broad with higher energy instead of a bright bandgap emission, which might be related to the defects created during the sample preparation.For the part on GQDs, the optical spectroscopy results indicate that GQDs are individualized in dispersions rather than in the form of aggregates. Then by means of microphotoluminescence, we directly address the intrinsic properties of single GQDs. Second-order photon correlation measurements reveal that GQDs exhibit single-photon emission with a high purity. Notably, the emission of GQDs has good photo-stability with high brightness. As a first example of the optical tunability of GQDs through the control of their structure, we observe that the emission of single edge-chlorinated GQDs is redshifted by almost 100 nm while maintaining the single-photon emission
19
Wu, Kehuey. "Strain effects on the valence band of silicon piezoresistance in p-type silicon and mobility enhancement in strained silicon pMOSFET /". [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0008390.
Testo completo
20
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.
Testo completo
21
Isaev, Leonid. "Spontaneous polarization effects in nanoscale systems based on narrow-gap semiconductors". Virtual Press, 2005. http://liblink.bsu.edu/uhtbin/catkey/1328116.
Testo completoAbstract (sommario):
In the framework of the two-band (Dirac) model, we analyze the electronic structure of nanoscale systems, based on narrow-gap semiconductors of Pb,_xSnx (Se, S) type. Themain attention is paid to the influence of properties of the surface, encoded in appropriate boundary conditions, on the size-quantized spectrum. From this point of view we consider two types of systems: spherical (quantum dots) and quasi one-dimensional (films).It is shown that the spectrum of the spherical quantum dot consists not only of usual size-quantized states, located above the gap edge, but also surface modes residing inside the gap. Such states manifest themselves in the far infrared part of the absorption spectrum, the measurement of which allows one to extract information about the dot surface.Next, we consider a film with the energy gap modulated in the <111> (growth) direction. It is shown that the spectrum of the infinite crystal possesses a supersymmetrical structure. The film boundaries, generally speaking, destroy the supersymmetry, i.e. size-quantized subbands turn out to be spin-split. However, there exists a class of boundary conditions that do not lift spin degeneracy. Physically, in this case there is no band mismatch at interfaces. Our central statement, therefore, consists of the following: even when the inversion symmetry is destroyed by the bulk inhomogeneity, the spin-splitting of the spectrum is a purely surface effect. This is illustrated on a simple example, when the energy gap varies linearly over the film width.Finally, we investigate the role of boundary conditions in the problem of scattering of spinor waves by a quantum dot. It is shown that the existence of surface states greatly modifies the scattering data; in particular, outgoing waves may turn out to be fully polarized.Department of Physics and Astronomy
22
Tran, Lien. "InSb semiconductors and (In,Mn)Sb diluted magnetic semiconductors". Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2011. http://dx.doi.org/10.18452/16334.
Testo completoAbstract (sommario):
Im Rahmen dieser Arbeit wurden InSb- und verdünnt-magnetische In_{1-x}Mn_xSb Filme mittels Gasquellen-Molekularstrahlepitaxie hergestellt und deren strukturelle und elektronische Eigenschaften untersucht. Die 2 μm InSb-Dünnschichten wurden sowohl auf GaAs(001)-Substrat als auch um 4° in Richtung [110] fehlgeschnittenem Si(001)-Substrat hergestellt. Optimierte InSb-Schichten direkt auf GaAs zeigen eine hohe kristalline Qualität, niedriges Rauschen und eine Elektronenbeweglichkeit von 41100 cm^2/Vs bei 300 K. Die Ladungsträgerkonzentration beträgt etwa 2,9e16 cm^{-3}. Um InSb-Dünnschichten guter Qualität auf Si-Substrat zu realisieren, wurden fehlgeschnittene Substrate benutzt. Zur Reduzierung der Gitterfehlanpassung wurden Pufferschichten gewachsen. Eine Elektronenmobilität von 24000 cm^2/Vs und Ladungsträgerkonzentration von 2,6e16 cm^{-3} wurden bei 300 K nachgewiesen. Diese Probe enthält ein 0,06 μm GaAs/AlSb-Supergitter als Pufferschicht (Wachstumstemperatur war 340°C). Diese Probe zeigt der höheren Dichte der Microtwins und Stapelfehler als auch den Threading-Versetzungen in der schnittstellennahen Region geschuldet. Die Deep-Level Rauschspektren zeigen die Existenz von Deep-Levels sowohl in GaAs- als auch in Si-basierten Proben. Die InSb-Filme auf Si-Substrat zeigen einen kleineren Hooge-Faktor im Vergleich zu Schichten auf GaAs (300 K). Unter Anwendung der optimierten Wachstumsbedingungen für InSb/GaAs wurden verdünnt-magnetische In_{1-x}Mn_xSb-Schichten (bis zum 1% Mangan) auf GaAs (001)-realisiert. Mn verringert die Gitterkonstante und damit den Grad der Relaxation von (In,Mn)Sb-Filmen. In den Proben befindet sich Mn in zwei magnetischen Formen, sowohl als verdünnt-magnetischer Halbleiter (In,Mn)Sb, als auch als MnSb-Cluster. Die Cluster dominieren auf der Oberfläche. Die Curie-Temperatur, Tc, unterscheidet sich für die beiden Formen. Für (In,Mn)Sb ist Tc kleiner als 50 K. Die MnSb-Cluster zeigen dagegen ein Tc über 300 K.This dissertation describes the growth by molecular beam epitaxy and the characterization of the semiconductor InSb and the diluted magnetic semiconductor (DMS) In_{1-x}Mn_xSb. The 2 µm-thick InSb films were grown on GaAs (001) substrate and Si (001) offcut by 4° toward (110) substrate. After optimizing the growth conditions, the best InSb films grown directly on GaAs results in a high crystal quality, low noise, and an electron mobility of 41100 cm^2/V s Vs with associated electron concentration of 2.9e16 cm^{-3} at 300 K. In order to successfully grow InSb on Si, tilted substrates and the insertion of buffer layers were used. An electron mobility of 24000 cm^2/V s measured at 300 K, with an associated carrier concentration of 2.6e16 cm^{-3} is found for the best sample that was grown at 340°C with a 0.06 μm-thick GaSb/AlSb superlattice buffer layer. The sample reveals a density of microtwins and stacking faults as well as threading dislocations in the near-interface. Deep level noise spectra indicate the existence of deep levels in both GaAs and Si-based samples. The Si-based samples exhibit the lowest Hooge factor at 300 K, lower than the GaAs-based samples. Taking the optimized growth conditions of InSb/GaAs, the DMS In_{1-x}Mn_xSb/GaAs is prepared by adding Mn (x < 1%) into the InSb during growth. Mn decreases the lattice constant as well as the degree of relaxation of (In,Mn)Sb films. Mn also distributes itself to result in two different and distinct magnetic materials: the DMS (In,Mn)Sb and clusters MnSb. The MnSb clusters dominate only on the surface. For the DMS alloy (In,Mn)Sb, the measured values of Curie temperature Tc appears to be smaller than 50 K, whereas it is greater than 300 K for the MnSb clusters.
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Oliva, Vidal Robert. "High-pressure optical and vibrational properties of InN and InGaN". Doctoral thesis, Universitat de Barcelona, 2016. http://hdl.handle.net/10803/400490.
Testo completoAbstract (sommario):
This thesis is devoted to the study of the optical and vibrational properties of indium nitride (InN) and indium gallium nitride (InGaN) at room and high-pressure conditions. For this purpose, we have employed spectroscopic tools such as absorption spectroscopy or Raman scattering in order to investigate a series of InN and InGaN thin films grown with different methods and on different substrates. For the high-pressure measurements, we have employed the diamond anvil cell technique.
High-pressure optical absorption experiments on InN epilayers have allowed us to observe the direct-to-indirect bandgap transition at 15 GPa, where wurtzite InN (w-InN) transits to the rocksalt polymorph (rs-InN). Investigating w-InN samples with different levels of residual electron density, we have been able to estimate the bandgap pressure coefficient of intrinsic w-InN (32 meV/GPa). In addition, we have measured the indirect bandgap of rs-InN and its pressure dependence. We have also performed FTIR reflectivity measurements to determine the pressure dependence of the refractive index of w-InN and rs-InN. By fitting the experimental results with a model for the dielectric function, we have determined the pressure coefficient of the high-frequency dielectric constant of both phases.
The pressure coefficient of the phonon frequencies of w-InN and their respective mode Grüneisen parameters have been measured by high-pressure Raman spectroscopy. After the wurtzite-to-rocksalt phase transition and the rocksalt-to-wurtzite backtransition upon decompression, the Raman features of both (amorphized) phases have been assigned in terms of first-principle lattice-dynamics calculations. Raman measurements on a heavily doped n-type sample have allowed us to detect a longitudinal-optical plasmon coupled mode, from which we have evaluated the pressure dependence of the electron effective mass of w-InN. With the aim of comparing the pressure behavior of the optical modes of rs-InN with that of a material exhibiting the rocksalt structure at ambient conditions, a high-pressure Raman-scattering study on rocksalt CdO is also presented.
The optical and vibrational properties of the InGaN alloy as a function of composition have also been investigated. The composition dependence of the fundamental bandgap of InGaN has been studied with optical absorption, and high-pressure photoluminescence measurements have been carried out to determine the pressure coefficients of the optical emission. In turn, the optical and acoustic phonons of InGaN have been investigated as a function of alloy composition at ambient conditions. From Raman measurements on InGaN thin films, we have found that strain importantly affects the dependence on composition of the optical modes. An analysis to correct for the strain-induced shifts as well as to assess the effect of compositional inhomogeneities on the optical phonon frequencies of InGaN is provided.
For the study of the acoustic modes of InGaN at room pressure, we have performed high-resolution Brillouin spectroscopy measurements, which have allowed us to determine the velocity of the surface acoustic waves of InGaN as a function of composition. With the aid of theoretical simulations based on the Green’s function formalism, these velocities have been used to evaluate the compositional dependence of the elastic constants of the alloy. Additional Raman-scattering measurements on InGaN/GaN superlattices have allowed us to detect the folded acoustic modes and observe the linear dispersion of the LA modes in InGaN, as predicted by elastic continuum theory.
Finally, the behavior of the optical modes of InGaN under pressure has been investigated by Raman spectroscopy on epilayers grown on GaN/Al2O3 and Si(111) substrates. This study, which
was initially aimed at determining the Grüneisen parameters of the optical phonons, has revealed that the experimental results strongly depend on the compressibility of the substrate material. We conclude that the pressure coefficients of free-standing InGaN should follow a linear dependence between those of GaN and InN.
24
Cole, Eric D. "On the feasibility and application of optical p to n inversion". Thesis, Virginia Tech, 1985. http://hdl.handle.net/10919/45719.
Testo completoAbstract (sommario):
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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Pyke, Daniel James. "Hydrogen evolution and transport in semiconductors". Phd thesis, Canberra, ACT : The Australian National University, 2014. http://hdl.handle.net/1885/125142.
Testo completoAbstract (sommario):
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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Mashigo, Donald. "Raman spectroscopy of ternary III-V semiconducting films". Thesis, Nelson Mandela Metropolitan University, 2009. http://hdl.handle.net/10948/1011.
Testo completoAbstract (sommario):
The III-V semiconductor compounds (i.e. In Ga As x 1-x , 1 x x InAs Sb - , In Ga Sb x 1-x and Al Ga As x 1-x ) have been studied using room temperature Raman spectroscopy. X-ray diffraction has been used as a complementary characterization technique. In this study all the III-V semiconductor compounds were grown by metal organic chemical vapour deposition (MOCVD) on GaAs and GaSb substrates. The layers were studied with respect to composition, strain variation and critical thickness. Raman spectroscopy has been employed to assess the composition dependence of optical phonons in the layers. The alloy composition was varied, while the thickness was kept constant in order to investigate compositional effects. A significant frequency shift of the phonon modes were observed as the composition changed. The composition dependence of the phonon frequencies were described by linear and polynomial expressions. The results of this study were compared with previous Raman and infrared work on III-V semiconductor compounds. Strain relaxation in InGaAs and InGaSb has been investigated by Raman and X-ray diffraction. Measurements were performed on several series of layers. For each series, the thickness was varied, while keeping the composition constant. For a given composition, the layer thicknesses were such that some layers should be fully strained, some partially relaxed and some fully relaxed. The Raman peak shifts and XRD confirm that a layer grows up to the critical thickness and then releases the strain as the thickness increases. Critical layer thickness values measured in this study were compared with published data, in which various techniques had been used to estimate the critical thickness.
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Krishnamurthy, Nicole Andrea. "Mixed material integration for high speed applications". Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/14684.
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Sun, Yunlong. "Laser processing optimization for semiconductor based devices /". Full text open access at:, 1997. http://content.ohsu.edu/u?/etd,3.
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Kelkar, Kapil S. "Semiconductor modeling for multi-layer, high field photo switch using sub-bandgap photons /". free to MU campus, to others for purchase, 2004. http://wwwlib.umi.com/cr/mo/fullcit?p1421147.
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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.
Cerca il testo completoAbstract (sommario):
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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Li, Bin. "Electrical bistability in organic semiconductors and spin injection using organic magnetic semiconductor". The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1334864514.
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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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Sankin, Igor. "Edge termination and RESURF technology in power silicon carbide devices". Diss., Mississippi State : Mississippi State University, 2006. http://library.msstate.edu/etd/show.asp?etd=etd-12162005-141206.
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Nayak, Rekha R. "Dimensionally confined semiconductors". Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.311992.
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Bigger, James R. K. "Dislocations in semiconductors". Thesis, University of Oxford, 1992. http://ora.ox.ac.uk/objects/uuid:2be9288d-caee-4070-b535-b8fc6406b4d1.
Testo completoAbstract (sommario):
A set of codes with 3D periodic boundary conditions has been developed to model dislocations in semiconductors. Several schemes have been used to investigate the atomic structure of dislocations; classical potentials incorporated in a Molecular Dynamics framework, a tightbinding k-space scheme and ab initio pseudopotential codes developed at Cambridge and Edinburgh. An error has been detected in previous work that modelled dislocations using periodic boundary conditions. It is demonstrated, for the 90° and 30° Shockley partials, that a mismatch at the periodic boundaries leads to erroneous atomic and particularly electronic structures. A new approach is proposed which through its geometry obviates this problem. The Stillinger Weber potential has been found to predict a completely new type of reconstruction for the 90° partial. Recent work by other authors confirms this and predicts significantly different results to earlier work. A thorough investigation has been made into the bonding processes involved in the core of the 90° partial. This study has involved reproducing much of the earlier work to understand why there has been such poor agreement between various authors. The reconstruction of the 90° partial is found to involve a symmetry lowering displacement intimately connected to its electronic structure. The band-gap is predicted to be clear of states, except for the possibility of shallow states at both band edges, which contradicts the findings of the most recent work on this partial by other authors. The interaction of phosphorous with the 90° partial has been studied using the tightbinding model. The Hamiltonian has been parameterised by comparing the predictions to an earlier ab initio cluster method study. Good qualitative agreement with the ab initio work is obtained, including the prediction of a strong dislocation locking effect by phosphorous. Preliminary studies on the unreconstructed 30° partial show that phosphorous is strongly bound to the three-fold coordinated sites resulting in no states in the indirect band-gap. The modelling of interstitial copper at the core of the 90° partial has been initiated. The ab initio codes have been used and new silicon and copper pseudopotentials tested. The first attempt to model copper located interstitially in the core was not successful and the reasons for this have been identified. However, it is evident from this investigation that the neutral copper strongly repels and does not form bonds with the surrounding silicon atoms. A review is given of two techniques that have been developed to obtain the thermally averaged structure and concentration of vacancies at dislocations, together with a preliminary investigation on the Frank partial.
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Hodgson, Michael John. "Bonding in semiconductors". Thesis, University of Cambridge, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240971.
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Baklar, Mohammed Adnan. "Processing organic semiconductors". Thesis, Queen Mary, University of London, 2010. http://qmro.qmul.ac.uk/xmlui/handle/123456789/1311.
Testo completoAbstract (sommario):
In recent years, there has been a considerable interest in organic semiconducting materials due to their potential to enable, amongst other things, low-cost flexible opto-electronic applications, such as large-area integrated circuitry boards, light-emitting diodes (OLEDs) and organic photovoltaics (OPVs). Promisingly, improved electronic performance and device structures have been realized with e.g. OLEDs entering the market and organic field-effect transistors (OFETs) reaching the performance of amorphous silicon devices; however, it would be too early to state that the field of organic semiconductors has witnessed the sought-after technological revolution. Initial progress in the field was mostly due to synthetic efforts in the form of enhanced regularity and purity of currently used materials, the creation of new molecular species, etc. In this thesis we show that the advancement of physico-chemical aspects – notably materials processing – and the realisation of increased order and control of the solid state structure is critical to realize the full intrinsic potential that organic semiconductors possess. We first investigated how the bulk charge-transport properties of the liquid-crystalline semiconductor poly(2,5-bis (3-dodecylthiophen-2-yl)thieno[3,2-b]thiophenes) (pBTTT-C12) can be enhanced by annealing in the mesophase. To this end, temperature treatment of a period of hours was necessary to realize good bulk charge transport in the out-of-plane directions. This behaviour is in strong contrast to in-plane charge transport as measured in thin-film field-effect structures, for which it was shown that annealing times of 10 min and less are often sufficient to enhance device performance. Our observation 4 may aid in future to optimize the use of pBTTT polymers in electronic devices, in which good bulk charge transport is required, such as OPVs. In the second part of thesis, we explored ink-jet printing of pBTTT-C12, in order to realize precise deposition of this material into pre-defined structures. In organic electronic applications this can, amongst other things, enable deposition of different semiconductors or reduction of the unwanted conduction pathways that often result in undesirable parasitic ‘cross-talk’, for instance, between pixels in display products. We demonstrate the integration of ink-jet printed transistors into unipolar digital logic gates that display the highest signal gain reported for unipolar-based logic gates. Finally, recognizing that a broad range of conjugated organic species fall in the category of “plastic crystals”, we explored the option to process this class of materials in the solid state. We find that solid-state compression moulding indeed can effectively be applied to a wide spectrum of organic small molecular and polymeric semiconductors without affecting adversely the intrinsic favourable electronic characteristics of these materials. To the contrary, we often observe significantly enhanced [bulk] charge transport and essentially identical field-effect transistor performance when compared with solution- or melt-processed equivalents. We thus illustrate that fabrication of functional organic structures does not necessitate the use of solution processing methods, which often require removal of 99 wt% or more of solvent, or precursor side-products, nor application of cumbersome vapour deposition technologies.
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Durandurdu, Murat. "Polyamorphism in Semiconductors". Ohio University / OhioLINK, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1040060243.
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Mahadik, Nadeemullah A. "Non-destructive x-ray characterization of wide-bandgap semiconductor materials and device structures". Fairfax, VA : George Mason University, 2008. http://hdl.handle.net/1920/3404.
Testo completoAbstract (sommario):
Thesis (Ph.D.)--George Mason University, 2008.Vita: p. 104. Thesis director: Mulpuri V. Rao. Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Electrical and Computer Engineering. Title from PDF t.p. (viewed Mar. 17, 2009). Includes bibliographical references (p. 99-103). Also issued in print.
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Cornet, i. Calveras Albert. "Estudio por medio de espectroscopia picosegundo de los compuestos II-VI sometidos a fuerte excitación óptica". Doctoral thesis, Universitat de Barcelona, 1987. http://hdl.handle.net/10803/665808.
Testo completoAbstract (sommario):
En la pasada década, se han observado nuevas bandas de luminescencia en los semiconductores cuando son excitados fuertemente por medio de láseres (fotoexcitacion). La interpretación del origen de estas bandas era variado y ha sido objeto de controversias y discusiones entre los diferentes autores. Finalmente, por medio de experiencias complementarias (efecto Raman, scattering con luz I.R., espectroscopia de excitación, fotoconducción)) se ha probado que en CuCl tiene lugar la formación de moleculas biexcitónicas y que en Ge y en Si, las altas excitaciones producen un plasma electrón-hueco.
Sin embargo, en los compuestos II-VI, la interpretación es más difícil, y si bien en alguno de ellos (ZnO) ha quedado bien establecida la existencia de procesos de colisión inelásticos, en general, hay controversias acerca de la interpretación de las llamadas bandas M y P.
Generalmente, una de las características comunes de todos los experimentos citados es el uso de láseres nanosegundo para el estudio, por medio de la espectroscopia integrada en el tiempo (técnicas de luminescencia o de ganancia-absorción), de las propiedades de dichos materiales sometidos a excitaciones fuertes. Estas condiciones experimentales dan lugar a ciertas dificultades, que se resuelven con el empleo de técnicas picosegundo, ya que en efecto, el uso de un láser psicosegundo de alta potencia (láser YAG), permite la excitación homogénea de la muestra en la dirección de la excitación, por medio de la absorción a dos fotones. Además, dado que la duración de la impulsión es menor oue el tiempo de vida de las diferentes excitaciones elementales (excitón, biexcitón, plasma electron-hueco...) podemos obtener una dinámica de la relajación de portadores que tiene lugar al final de la impulsión excitadora y, con ello, clarificar algunas de las contradicciones citadas anteriormente.
En el dominio de las fuertes excitaciones picosegundo, los experimentadores pueden escoger entre una excitación “caliente” pero relativamente homogénea (excitación a dos fotones) y una excitación “fría” (con un fotón de energía) pero inhomogénea. El primer método nos conduce a .la utilización de láseres de potencia y el segundo, al empleo de láseres de longitud de onda reglable. Nosotros hemos empleado el método de la excitacion caliente. Este método exige tener en cuenta los problemas de termalización del sistema electrón-hueco excitado. Dado que esta cuestión es esencial en este tipo de experiencias, gran parte de esta memoria ha sido consagrada al estudio de dicha termalización.
El capítulo I contiene la presentación del conjunto experimental y algunos datos de los materiales estudiados CdSe y CdS. En el capítulo II, calcularemos un modelo simple para prever la cinética de temperatura del plasma. Finalmente, el capitulo III contiene una discusiónsobre la naturaleza de las diferentes líneas de luminescencia del espectro de los semiconductores II-VI estudiados.
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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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Farner, William Robert. "On-chip probe metrology /". Online version of thesis, 2008. http://hdl.handle.net/1850/6207.
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Chan, Wan Tim. "CMOS-compatible zero-mask one time programmable (OTP) memory design /". View abstract or full-text, 2008. http://library.ust.hk/cgi/db/thesis.pl?ECED%202008%20CHANW.
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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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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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Radovanovic, Pavle V. "Synthesis, spectroscopy, and magnetism of diluted magnetic semiconductor nanocrystals /". Thesis, Connect to this title online; UW restricted, 2004. http://hdl.handle.net/1773/8494.
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Yoo, Jung-Woo. "Multiple photonic response in organic-based magnetic semiconductor". Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1167406887.
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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.
Testo completoAbstract (sommario):
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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Stoica, Vladimir A. "Optical characterization of compound semiconductors using photoconductivity and photoreflectance". Morgantown, W. Va. : [West Virginia University Libraries], 2000. http://etd.wvu.edu/templates/showETD.cfm?recnum=1468.
Testo completoAbstract (sommario):
Thesis (M.S.)--West Virginia University, 2000.Title from document title page. Document formatted into pages; contains iv, 68 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 67-68).
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Ward, Martin B. "Squeezed light in semiconductors". Thesis, University of Oxford, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.270175.
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