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1
Moehlmann, Benjamin James. "Spin transport in strained non-magnetic zinc blende semiconductors." Diss., University of Iowa, 2012. https://ir.uiowa.edu/etd/3353.
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The problem of spin manipulation via the spin-orbit interaction in nonmagnetic semiconductors in the absence of magnetic fields is investigated in this work. We begin with a review of the literature on spin dynamics in semiconductors, then discuss the semi-empirical k ⋅ p method of calculating direct-gap semiconductor properties, which we use to estimate material parameters significant for manipulation of spin even in the absence of a magnetic field. The total effective magnetic fields and precession lengths are calculated for a variety of quantum well orientations, and a class of devices are proposed that will allow for all-electric arbitrary manipulation of spin orientations.
The strain- and momentum-dependent spin splitting coefficient C3 has been calculated using a fourteen band Kane k⋅p model for a variety of III-V semiconductors as well as ZnSe and CdSe. It is observed that the spin-splitting parameters C3 and γ, corresponding to the strain-induced spin-orbit interaction and Dresselhaus coefficient, are sensitive to the value of the inter-band spin-orbit coupling Δ− between the p valence and p̄ second conduction band in all cases. The value of Δ− has therefore been recalculated in these materials using a tight-binding model and modern experimental values of the valence and second conduction band spin-orbit splittings.
The total effective magnetic field and precession length of spins in strained quantum wells in the (001), (110), and (111) planes are derived with consideration for all known effective magnetic fields except those due to interface effects in non- common-atom heterostructures (native inversion asymmetry). The orientation of the k-linear Dresselhaus field and the strain-dependent fields vary strongly with the growth axis of the quantum well. The precession length in the (110) and (001) cases can achieve infinite anisotropy, while the precession length of (111) quantum wells is always isotropic.
We find that the electronic spin rotation induced by drift transport around a closed path in a wide variety of nonmagnetic semiconductors at zero magnetic field depends solely on the physical path taken. Physical paths that produce any possible spin rotation due to transport around a closed path are constructed for electrons experiencing strain or electric fields in (001), (110), or (111)-grown zinc blende semiconductor quantum wells. Spin decoherence due to travel along the path is negligible compared to the background spin decoherence rate. The small size of the designed paths (< 100 nm scale in GaAs) may lead to applications in nanoscale spintronic circuits.
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Orange, Catherine Louise. "Spin-flip Raman scattering of wide band gap semiconductor heterostructures." Thesis, University of East Anglia, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267773.
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Pravica, Luka. "Polarised electron studies of spin-dependent interactions in zinc and krypton atoms." University of Western Australia. School of Physics, 2006. http://theses.library.uwa.edu.au/adt-WU2006.0063.
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[Truncated abstract.] An apparatus has been built, tested and characterised with greatly increased precision and accuracy to enable spin-polarised electron impact explorations of angular momentum effects in atoms. A combination of experimental, computational and interpretative studies has revealed new phenomena. In zinc the polarisation of the radiated photons from excited and ionised-with-excited atoms was measured in terms of integrated Stokes parameters (P1, P2 and P3) and related to electron exchange and spin-orbit interaction using normalised state multipoles.
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Karimov, Oleg Zufarovitch. "Spin-flip Raman spectroscopy of ZnCdSe-based heterostructures." Thesis, University of Bath, 2000. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341007.
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Adair, Antony. "Observed super-spin class behavior in Ni₀.₅Zn₀.₅Fe₂O₄ nanoparticles." To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2009. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.
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Napier, Stuart A. "Electron correlation and spin-dependent effects in the electron impact excitation of zinc atoms." University of Western Australia. School of Physics, 2009. http://theses.library.uwa.edu.au/adt-WU2009.0098.
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[Truncated abstract] This work investigated electron correlation and spin-dependent effects in electron scattering from zinc for incident electron energies from the lowest excitation threshold at 4.003 eV to 50 eV. Experiments were performed using a crossed-beams electron impact spectrometer, which included an unpolarised electron gun, and also a spin-polarised electron gun. The apparatus was tested, and shown to be operating well, by repeating past studies of electron scattering from helium and argon. Emission cross sections for the 4s4p 3P1, 4s4p 1P1, 4s5s 3S1, 4s4d; 5d; 6d 3D1;2;3 and 4s4d; 5d 1D2 states were measured from the respective thresholds to 50 eV. These were compared with Convergent Close-Coupling (CCC) and B-spline R-matrix (BSRM) calculations of the 4s4p 3P1, 4s4p 1P1, 4s5s 3S1, 4s4d 1D2 and 4s4d 3D1;2;3 emission cross sections. There are serious discrepancies between the theories, and between the theories and experiment, which indicates strong continuum coupling and innershell excitation effects in the electron excitation of zinc. The differential elastic scattering signal at scattering angles of 30 , 54 , 90 and 110 was measured for incident electron energies from just below the lowest excitation threshold at 4.003 eV, to the ionisation threshold at 9.394 eV. Some assignments given by Sullivan et al [1] and Zatsarinny and Bartschat [2] were confirmed by the present experiment. An area of disagreement in the literature concerning the nature of a feature observed at the 4s4p 1P1 threshold at 5.796 eV was resolved in favour of Zatsarinny and Bartschat, who assign the feature as a cusp. ... Below the ionisation threshold, the 4s4p 3P1 photon excitation function supports the assignment of the near-4s4p 1P1 threshold feature as a cusp. Some of the overlapping negative-ion resonances which were observed near 7.5 eV in the 4s4p 3P1, 4s4p 1P1 and 4s5s 3S1 photon excitation functions were assigned with the assistance of the BSRM calculations of Zatsarinny and Bartschat. However, continuum coupling effects above 8 eV seem to cause the theoretical negative-ion resonance predictions to break down. Above the ionisation threshold, the near-11 eV negative-ion resonance effects depend on the configuration n, L and S of the neutral state excitation observed. This may be due to the properties of the mixed negative ion component states. Postcollision interaction (PCI) effects the 4s5s 3S1, 4s4d; 5d; 6d 3D1;2;3 and 4s4d; 5d 1D2 photon excitation functions. The PCI mechanism can populate the 4s4d; 5d; 6d 3D1;2;3 and 4s4d; 5d 1D2 states because the scattered and ejected electrons have a similar energy, and can thus exchange a large amount of orbital angular momentum. The present work demonstrates that electron correlation effects, especially those associated with innershell excitation, are very significant in electron scattering from zinc. Existing theoretical models of electron scattering from zinc inadequately treat electron correlations, and as a result of this are inaccurate, as shown here. The studies presented here should guide the development of models that accurately describe the innershell excitation effects, which are important for zinc and a great many other atoms.
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Campos, Tiago de. "Spin-orbit coupling effects and g-factors in zinc-blende InSb and wurtzite InAs nanowires using realistic multiband k · p method." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/76/76132/tde-30012018-163011/.
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Spin-dependent phenomena in semiconductor nanowires have recently gained a lot of attention, in special because these nanostructures can be a viable setup to study exotic states of matter like the Majorana fermions. One of the key ingredients to accommodate the Majorana zero modes is the spin-orbit coupling in the nanowires, which has been usually treated with two-band Hamiltonians. The spin-orbit coupling in semiconductors arise from two distinct sources being the bulk inversion asymmetry, when the unit cell does not present inversion symmetry, e.g. when the crystal unit cell is composed by two different atoms, and the structural inversion asymmetry, when the whole system does not have a mirror symmetry. To describe the system these effective models take as input, parameters that are dependent on the system configuration and measurement setups. Although these effective models have been successful in determine relevant physical properties, a more realistic description of the interacting energy bands is required, specially in quantum confined systems where the interplay between both sources of spin-orbit coupling can change the systems properties in non-trivial ways. For instance, in quantum wells there is an anisotropy of the g-factor due to the quantum confinement and structural inversion asymmetry. Furthermore, the in-plane g-factor also have an anisotropy which is due to the intrinsic spin-orbit coupling and it is not captured by these effective models. In this study, we use realistic multiband k · p Hamiltonians, including both spin-orbit coupling mechanisms, to determine the band structure of zincblende InSb and wurtzite InAs nanowires under a transverse electric field. We analyze the effects of the lateral quantum confinement for a hexagonal cross-section geometry and of the change in growth directions, extracting the relevant physical parameters for the first conduction subband. We found that the g-factors are heavily dependent on the quantum confinement and nanowire orientation, with in-plane/out-of-plane anisotropies up to 3%. We also found that for zinc-blende nanowires the extrinsic spin-orbit coupling is dominant over the intrinsic one whereas, for wurztize, the opposite behavior holds. In order to assess if the nanowires could host the aforementioned Majorana zero modes we investigate under which circumstances the topological phase transition occurs, using the Bogoliubov-de Gennes formalism to couple the nanowire with a superconductor, and we found that using realistic and experimental feasible parameters, indeed, the phase transition occurs. In conclusion, our systematic investigation of nanowires shows that the spin-orbit coupling energy can be fine tuned by the external electric field in experimentally achievable setups that ultimately could guide the search for the elusive Majorana modes. Moreover, our numerical approach is not restricted to a specific material or dimensionality and can be used to study others systems to provide useful insights into the electronic and spintronic fields.Recentemente, fenômenos dependentes de spin em nanofios semicondutores se tornaram uma área de pesquisa ativa especialmente porque essas nanoestruturas podem ser viáveis para o estudo de estados exóticos da matéria como, por exemplo, os férmions de Majorana. Um dos ingredientes chave para que esses modos de excitação possam existir em nanofios é o acoplamento spin-órbita, o qual tem sido usualmente tratado com modelos de duas bandas. O acoplamento spin-órbita em semicondutores aparece de duas fontes distintas sendo elas a assimetria de inversão no bulk, quando a célula unitária do cristal não possui simetria de inversão, por exemplo, quando é formada por dois átomos diferentes, e a assimetria de inversão estrutural, quando o sistema como um todo não possui simetria de inversão. Para descrever o sistema, os modelos efetivos de duas bandas usam como entrada parâmetros que dependem tanto do sistema específico quanto da configuração do arranjo experimental. Apesar desses modelos terem sucesso em descrever algumas das propriedades físicas relevantes, uma descrição mais realística da interação entre as bandas de energia se faz necessária, especialmente em sistemas com confinamento quântico onde a ação combinada das duas fontes de acoplamento spin-órbita muda as propriedades do sistema de maneira não-trivial. Por exemplo, o fator giromagnético em poços quânticos é anisotrópico devido aos efeitos de ambos, confinamento quântico e a assimetria de inversão estrutural. Ademais, o fator giromagnético ao longo do plano também possui uma anisotropia, a qual tem origem no acoplamento spin-órbita intrínseco do sistema e não é capturada por esses modelos efetivos. Nesse estudo, nós usamos Hamiltonianos k · p multibanda, incluindo ambos os mecanismos de acoplamento spin-órbita, para determinar a estrutura de bandas de nanofios de InSb na fase blenda de zinco e InAs na fase wurtzita sob a ação de um campo elétrico transversal. Nós analisamos os efeitos do confinamento quântico lateral, para fios com seção transversal hexagonal, e diferentes direções de crescimento, extraindo parâmetros físicos relevantes para a primeira sub-banda de condução. Nós encontramos que os fatores giromagnéticos são fortemente influenciados pelo confinamento quântico e orientação dos nanofios, com anisotropias no plano e fora do plano de até 3%. Nós também encontramos que para nanofios de InSb na fase blenda de zinco, o acoplamento spin-órbita extrínseco domina o intrínseco enquanto que, em nanofios de InAs na fase wurtzita, vale o oposto. Para avaliar se os nanofios podem hospedar os modos de Majorana de energia zero nós investigamos sob quais circunstâncias a transição de fase topológica ocorre usando o formalismo de Bogoliubov-de Gennes para acoplar o nanofio a um supercondutor, e encontramos que usando nossos parâmetros e em condições experimentalmente factíveis, de fato, a transição de fase ocorre. Em conclusão, nossa investigação sistemática nos nanofios mostrou que o acoplamento spin-órbita pode ser ajustado por fontes externas, tais como um campo elétrico aplicado, e em configurações experimentais factíveis e que ultimamente pode guiar à busca dos elusivos modos de Majorana. Além do mais, nossa abordagem numérica não é restrita a esses materiais em específico e nem a nanofios, podendo ser usada para estudar outros sistemas provendo intuições úteis nos campos de eletrônica e spintrônica.
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Winarski, David J. "Synthesis and Characterization of Transparent Conductive Zinc Oxide Thin Films by Sol-gel Spin Coating Method." Bowling Green State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1434124579.
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Souag, Nadia. "Caractérisation par des mesures magnétiques de l'oxyde de zinc entrant dans la composition des varistances." Toulouse 3, 1987. http://www.theses.fr/1987TOU30310.
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Nous avons etudie le spectre de rpe en bande x d'un echantillon de zno degaze a haute temperature. Deux raies, respectivement situees a g=1,96 et g=2 290 k sont observees. Nous avons etudie leur evolution en position (valeur de g), largeur et intensite en fonction de la temperature entre 10 et 290 k. Nous avons etudie aussi la relaxation spin-reseau de cet echantillon par les techniques de saturation continue et de modulation sur la gamme de temperatures de 20 a 290 k. Nous en avons deduit une mesure de la temperature de debye. Nous avons egalement etudie un echantillon de zno dope au co#3o#4 qui montre un spectre de structure hyperfine bien resolu
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Ramashia, Thinavhuyo Albert. "Effect of the additional electron acceptor in hybrid ZnO: P3HT:PCBM spin-coated films for photovoltaic application." University of the Western Cape, 2015. http://hdl.handle.net/11394/4779.
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>Magister Scientiae - MScIn a quest for low operational and maintenance cost solar cell devices, organic photovoltaics remain a potential source of energy worthy to be explored. In order to generate cost- effective electricity from solar energy, either the efficiency of the solar cells must be improved or alternatively the manufacturing cost must be lowered. The power conversion efficiency (PCE) of organic photovoltaics is influenced by the choice of electron acceptor material, the structure of the polymer, the morphology of the film, the interfaces between the layers and the ratio between the electron acceptor material and the polymer. Nevertheless, efficiency is still limited compared to conventional silicon based PV cells due to low mobility of charge carriers with a short exciton diffusion length in the active layer. Currently, hybrid solar cells have been considered as one of the most promising concepts to address the limited efficiency of organic solar cells. Therefore in this thesis ZnO nanoparticles were synthesized using hydrothermal assisted method. These nanoparticles were incorporated in the poly (3-hexylthiophene) (P3HT):[6,6]-phenyl-C61-butyric acid methyl ester (PCBM), and used as additional acceptors of electrons released from the polymer donor material, with the anticipation to increase the electron mobility, and ultimately the PCE. The thermo-gravimetric analyses revealed improved thermal stability of P3HT upon incorporating ZnO in the polymer matrix. X-ray diffraction analyses revealed that the diffraction peaks shift to higher angles when incorporating the ZnO in the P3HT:PCBM surface and this is consistent with the Raman observation. The photovoltaic properties demonstrated that the addition of ZnO nanoparticles in P3HT:PCBM bulk-heterojunction increases PCE from a baseline of ∼1.0 % in the P3HT:PCBM system to 1.7% in the P3HT:PCBM:ZnO ternary system. The enhanced PCE was due to improved absorption as compared to its counterparts. Upon increasing the addition of ZnO nanoparticles in the P3HT:PCBM matrix, the PCE decreases, due to a large phase separation between the polymer, PCBM and ZnO induced by ZnO agglomerations which resulted in increased surface roughness of the active layer. These findings signify that incorporation of ZnO nanostructures in the P3HT:PCBM polymer matrix facilitates the electron transport in the photoactive layer which results to improved efficiency.
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Sati, Pascal. "Propriétés magnétiques et de résonance du Zn1-xCoxO : un matériau candidat pour l’électronique de spin." Aix-Marseille 3, 2007. http://www.theses.fr/2007AIX30034.
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Pour permettre de nouveaux développements de la Spintronique, il est nécessaire aujourd’hui d'élaborer un semiconducteur ferromagnétique à la température ambiante. L'oxyde de Zinc dopé par le Cobalt est à l'heure actuelle un candidat très prometteur, mais ses propriétés magnétiques restent toujours très discutées. Dans ce mémoire de thèse, nous présentons une étude de films minces de ZnO:Co (épitaxiés par jets moléculaires) se basant sur la Résonance Paramagnétique Electronique et la magnétométrie à SQUID. Cette étude, réalisée au sein du laboratoire L2MP et en collaboration avec le laboratoire CRHEA, a permis d'apporter de nouvelles informations sur les propriétés magnétiques et de résonance intrinsèques du ZnO:Co. Une anisotropie magnétique de type plan facile et des interactions d'échange antiferromagnétiques entre les ions Co2+ premiers voisins dans ZnO ont notamment été identifiées. De plus, le mécanisme à l’origine de l’élargissement des raies RPE du ZnO :Co a pu être déterminéRecently, Zn1-xCoxO has been actively explored as a possible room temperature ferromagnetic semiconductor, a key material for Spintronics. Nevertheless, its intrinsic magnetic properties remain still an open question. In this thesis manuscript, we report on the magnetic and resonance properties of ZnCo:O layers grown by plasma-assisted molecular beam epitaxy. From EPR and SQUID measurements performed at the L2MP laboratory, our study allows us to safely conclude on the existence of a huge magnetic anisotropy of an ‘easy plane’ type, and on the existence of nearest-neighbor Co2+ ions coupled antiferromagnetically. Moreover, we established, for the first time, that a combined effect of exchange and dipolar broadening is at the origin of the EPR linewidth in ZnO:Co
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BOULANGER, DANIEL. "Theorie du champ de ligandes des coefficients de couplage orbite-reseau et spin-reseau des ions d**(5) dans les composes ii-vi." Paris 6, 1988. http://www.theses.fr/1988PA066098.
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Developpement d'un modele moleculaire semi-empirique pour les ions d**(5). L'application aux calculs des coefficients de couplage orbite-reseau et des coefficients de couplage spin-reseau a donne de tres bons resultats
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Roger, Mélissa. "Nouveaux chélates [triazacyclononane-métaux de transition] : synthèse, complexation et premières applications." Phd thesis, Université de Bretagne occidentale - Brest, 2013. http://tel.archives-ouvertes.fr/tel-00966494.
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Les polyazamacrocycles trouvent de nombreuses applications dans le domaine de la complexation de cations métalliques ou d'anions. Le laboratoire à longtemps étudié la fonctionnalisation des dérivés tétraazamacrocycliques et leurs propriétés de complexation. Afin d'accroître le savoir-faire du laboratoire et d'explorer de nouvelles propriétés de complexation des polyamines cycliques, nous nous sommes intéressé à transposer ce savoir à la fonctionnalisation d'un macrocycle plus petit : le tacn. Ce travail repose sur la mise au point d'une nouvelle stratégie de fonctionnalisation sélective du tacn et la synthèse de nouveaux dérivés. Les composés obtenus ont permis l'étude de leurs propriétés de complexation vis-à-vis de différents métaux de transition. Les propriétés de complexes de cuivre (II) ont été étudiées pour des applications en imagerie TEP ou en radioimmunothérapie. La détection de zinc (II) basée sur une détection IRM par de nouvelles sondes ditopiques tacn-do3a a été étudiée. La complexation de fer (II) pour des applications en transition de spin ont également permis de déterminer les propriétés de complexation de dérivés du tacn.
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Helton, Joel Strader. "The ground state of the spin-1/2 kagomé lattice antiferromagnet : neutron scattering studies of the zinc-paratacamite mineral family." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/52786.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2009.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student submitted PDF version of thesis.
Includes bibliographical references (p. 201-214).
The magnetic properties of the geometrically frustrated quantum magnets clinoatacamite, Cu2(OH)3Cl, and herbertsmithite, ZnCu3(OH)6Cl2, are studied by means of neutron scattering measurements as well as specific heat, susceptibility, and mag-netization measurements. These materials are studied to investigate the nature of the ground state of the spin-1 2 kagomé lattice antiferromagnet, as such a system is considered ideal for the emergence of spin liquid physics. Clinoatacamite, a distorted kagomé lattice antiferromagnet with weak inter-plane coupling, undergoes a Néel or- dering transition at TN ~/~ 6.2 K and shows evidence of a static local moment in the disordered phase below 18 K. Our experiments suggest two-dimensional Ising fluctuations at the Néel transition. A proposed spin ordering model is developed that suggests an order structure below TN and two-dimensional short range order of the kagomé plane spins up to 18 K. The inelastic spectrum is analyzed in terms of spin waves in an ordered kagomé lattice antiferromagnet with a Dzyaloshinskii-Moriya interaction. Herbertsmithite is the first structurally perfect spin- 1 2 kagomé lattice antiferromagnet. Susceptibility, specific heat, and neutron scattering measurements show no sign of any spin freezing or transition to a long range ordered state down to 50 mK. The data shows magnetic excitations extending adjacent to the ground state, suggesting the lack of any measurable spin gap. Several hypotheses are explored as possible explanations for the apparent lack of a spin gap.
(cont.) Dynamic susceptibility data display an unusual scaling relation, suggesting proximity to a quantum critical point. In sum, a wide range of data suggest that herbertsmithite displays a disordered gapless spin liquid ground state.
by Joel Strader Helton.
Ph.D.
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Savoyant, Adrien. "Anisotropie magnétique des semi-conducteurs II-VI dopés au manganèse." Aix-Marseille 3, 2010. http://www.theses.fr/2010AIX30021.
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Cette thèse est une étude théorique de l'anisotropie magnétique, ionique et d'échange, des Semi-conducteurs Magnétiques Dilués (DMS), des matériaux pour l'électronique de spin. Nous avons passé en revue les différentes approches, numériques et perturbatives, utilisées par le passé dans le calcul de l'anisotropie ionique des ion S de transition (Cr+, Mn2+, Fe3+) puis avons mis au point un modèle microscopique réaliste d'ion S dans un semi-conducteur II-VI, prenant en compte les interactions électrostatiques avec l'ensemble du cristal, l'hybridation des électrons 3d de l'ion S avec ceux des anions premiers voisins, l'interaction spin-orbite et la répulsion coulombienne dans la couche 3d|. Un hamiltonien réaliste pour les impuretés magnétiques Mn2+ a ainsi été établi et ses valeurs propres ont été calculées exactement par un code numérique en Fortran 95 et de manière approchée par théorie des perturbations à l'ordre 4. Nous avons ensuite appliqué notre modèle au cas des trois DMS II-VI dopés au manganèse de structure wurtzite, ZnO :Mn, CdS :Mn et CdSe :Mn. Nos résultats sont en bon accord avec les mesures RPE d'anisotropie ionique et une corrélation hybridation/déformation est suggérée. Nous nous sommes ensuite intéressés au superéchange antiferromagnétique entre ions magnétiques dans les isolants magnétiques. Un calcul perturbatifs à l'ordre 4 a permis de calculer les constantes de superéchange d'une paire d'ions Mn2+ dans les DMS II-VI. Les résultats sont en bon accord avec les mesures de marches d'aimantation et de diffusion inélastique de neutrons. Nous avons pu expliquer l'observation de deux constantes d'échange premiers voisins dans les DMS wurtzite par un processus d'échange bouclé ferromagnétique présent uniquement pour les paires hors du plan hexagonal. Nou avons ainsi précisé la règle de Goodenough-Kanamori pour les ions 3d5This thesis is a theoretical study of ionic and exchange magnetic amsetropyof Diluted Magnetic Semiconductors (DMS), materials for spintronics. We have checked the various numerical and analytical approaches undertook before in order to calculate the single ion anisotropy of S-state transition ions (Cr+, Mn2+, Fe3+), and then have developed a realistic microscopic model of an S ion in a II-VI semiconductor, taking in account the electrostatic interaction with the whole crystal, hybridization of S ion 3d electrons with those of the nearest neighbors, spin-orbit interaction and iallia. D Coulomb repulsion. A realistic Hamiltonian for Mn2+ magnetic impurities has then been written and its eigenvalues have been exactly obtained by a F95 numerical code and approximatively by fourth order perturbation theory. We then have applied our model to the three wurtzite II-VI DMS doped by manganese, ZnO :Mn, CdS :Mn et OdSe :Mn. Our results are in good agreement with the EPR measurements of ionic anisotropy and a correlation between hybridization and deformation is suggested. We then have been interested by the antiferromagnetic superexchange between magnetic ions in insulators. A fourth order perfurbation theory allowed us to calculate the superexchange constants of an Mn2+ pair in II-VI DMS. Results are in good agreements with Magnetization Step (MST) and Inelastic Neutron Scattering (INS) experiments. By the way, we have been able to explain the observation of two nearest neighbors exchange constants in wurtzite DMS by a ferromagnetic Ring Exchange process, only presents for out-of-(hexagonal) plane pairs. The Goodenough-Kanamori rule has then been precised for the 3d5 ions
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Mekki, Berrada Mohamed Kamal. "Synthèse d'agglomérats multi-échelles de sulfure de zinc par precipitation homogène." Phd thesis, Ecole Nationale Supérieure des Mines de Saint-Etienne, 2007. http://tel.archives-ouvertes.fr/tel-00340827.
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Le sulfure de zinc obtenu par précipitation homogène présente une grande importance dans l'industrie des matériaux à propriétés optiques et électroniques, laquelle souhaiterait maîtriser son procédé de fabrication. Le sulfure de zinc correspondant, qui est sous forme agglomérée, a été choisi pour sa morphologie structurée : chaque agglomérat présente quatre échelles quant à la taille des particules le constituant. Il est préparé via la décomposition thermique de la thioacétamide dans une solution acide contenant le sulfate de zinc.La précipitation est effectuée dans un réacteur fermé et parfaitement agité. Le but de cette étude est de présenter une méthodologie originale pour suivre en continu les concentrations en ions et les caractéristiques du solide formé : la production et la disparition des ions sulfure libérés par la thioacétamide, la consommation des ions zinc, l'évolution de la sursaturation relative au produit précipité ZnS. et les caractéristiques morphologiques des particules de ZnS. Les capteurs utilisés sont des électrodes spécifiques, des cellules conductimétriques et une sonde turbidimétrique. D'autres méthodes d'analyses, telles que la microscopie électronique, la granulométrie et la diffraction des RX, complètent cette étude expérimentale.
La morphologie des grains de sulfure de zinc dépend des conditions opératoires : vitesse d'agitation, concentrations initiales en réactifs, pH et température. Le pH est le paramètre qui conduit à la plus grande variabilité morphologique. Nous présentons donc les résultats expérimentaux et l'interprétation correspondante issus de la précipitation de ZnS réalisée à différents pH.
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Benzid, Khalif. "Etude de l'effet de l'anisotropie magnétique sur la phase dynamique et sur la phase géométrique des bits quantiques de spins électroniques d'ions de métaux de transition Mn2+, Co2+, Fe3+ isolés et des complexes d'ions Fe3+ dans l'oxyde de zinc monocristallin." Thesis, Strasbourg, 2016. http://www.theses.fr/2016STRAE009/document.
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Nous avons étudié, par RPE impulsionnelle, la cohérence quantique et des spins électroniques des ions de transition Mn2+, Co2+, Fe3+, et des complexes Fe3+/Cs+ et Fe3+/Na+, tous présents dans le ZnO monocristallin. Nous avons trouvé que l’anisotropie magnétique peut altérer la cohérence de la phase dynamique des qubits des spins électroniques. Nous avons mesuré une faible décohérence pour les spins d’ions Mn2+et Fe3+ dans ZnO, qui ont tous deux une faible anisotropie magnétique uniaxiale, tandis que les ions Co2+ isolés avec une très forte anisotropie magnétique uniaxiale, une décohérence rapide a été mis en évidence. Nous avons trouvé que les spins électroniques des complexes de type Fe3+/Cs+, ayant un tenseur d’anisotropie magnétique plus complexe que la simple anisotropie uniaxiale des ions Fe3+ isolés, possèdent presque le même temps de décohérence. Par la méthode des perturbations, nous avons mis en évidence théoriquement un terme supplémentaire à la phase habituelle de Berry, dû à l’anisotropie magnétique et qui existe dans tout système ayant un spin S>1/2We studied by pulsed EPR (p-EPR), the quantum coherence of electronic spins qubits of isolated transition metal ions of Mn2+, Co2+, Fe3+ and Fe3+/Cs+ as well as Fe3+/Na+ complexes, all found as traces in mono-crystalline ZnO. Indeed, we experimentally demonstrated that the magnetic anisotropy can alter the coherence of the dynamic phase of electronic spins qubits. We found a small decoherence for Mn2+ and Fe3+, spins having a small uniaxial magnetic anisotropy, and on the contrary, we found a very strong decoherence for Co2+ spins having a very strong uniaxial magnetic anisotropy. We found that the electronic spins of the Fe3+/Cs+ complex, having a more complex tensor magnetic anisotropy compared to the simplest uniaxial one of isolated Fe3+ spins in ZnO, have almost the same coherence time. By the perturbation method, we have found theoretically an additional term to the usual geometric Berry phase, due to the magnetic anisotropy which exists in any system having a spin S>1/2
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Brown, Graeme. "Time-resolved ultrafast spectroscopy of wide-gap II-VI semiconductor quantum wells." Thesis, Heriot-Watt University, 2001. http://hdl.handle.net/10399/502.
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Saifi, Ali. "Contribution à l'étude des propriétés magnétiques des systèmes spinelles isolants CdCr2xIn2-2xS4 et ZnCr2xGa2-2xO4 : phases type verre de spin." Paris 6, 1986. http://www.theses.fr/1986PA066519.
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Ces systèmes présentent la percolation et la frustration. Le premier composé est ferromagnétique, tandis que le second présente des interactions antiferromagnétiques. On étudie en fonction de x les transitions de ces composés. Les transitions de phase du gallate ont été étudiées par effet Mössbauer. On a mis en évidence que pour x0,75 l'ordre magnétique tend vers un ordre caractéristique de la "vraie" phase verre de spin.
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Rehman, Zia-ur [Verfasser], Roland [Gutachter] Span, and Mandy [Gutachter] Gerber. "Process stability in biogas digesters : influencing parameters control using carbonate addition / Zia-ur Rehman ; Gutachter: Roland Span, Mandy Gerber ; Fakultät für Maschinenbau." Bochum : Ruhr-Universität Bochum, 2019. http://d-nb.info/1182682308/34.
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Egal, Magali. "Structure et propriétés des solutions et gel de cellulose-NaOH-Eau et leurs matériaux régénérés." Phd thesis, École Nationale Supérieure des Mines de Paris, 2006. http://pastel.archives-ouvertes.fr/pastel-00002229.
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Il est connu que la cellulose peut-être dissoute dans des solutions aqueuses d'hydroxyde de sodium dans un petit domaine de concentrations (6-10%NaOH) et de températures (-10°C/-4°C). Les solutions de cellulose ainsi obtenues ne sont pas stables et gélifient en fonction du temps et de la température. Il a également été montré que la présence d'additifs - tels qu'oxyde de zinc et urée - améliore la dissolution des fibres de cellulose et la stabilité des solutions. Afin de comprendre la structure des solutions de cellulose dans NaOH/eau avec et sans additifs, nous avons étudié les diagrammes de phase des solvants d'une part et l'influence de la cellulose sur les thermogrammes de DSC d'autre part. Nous avons ainsi pu déterminer (i) la limite de dissolution de la cellulose dans des solutions de NaOH/eau et NaOH/urée/eau et (ii) la nature des interactions entre les différentes espèces en solution : chaînes de cellulose, NaOH, urée, ZnO et eau. Nous avons également étudié les propriétés rhéologiques des solutions de cellulose dans NaOH/eau, NaOH/urée/eau et NaOH/ZnO/eau. La gélification des solutions de cellulose est d'une part retardée par la présence d'additifs et correspond à une diminution de la qualité du solvant quand la température augmente. Cependant le mécanisme de gélification reste le même pour les trois solvants étudiés. Pour finir, l'étude des propriétés mécaniques, et notamment la résistance à rupture, sur des objets de cellulose régénérée a montré l'importance des paramètres de gélification et de régénération.
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Chladil, Ladislav. "Studium jevů limitujících životnost sekundárních článků Ni-Zn." Doctoral thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2014. http://www.nusl.cz/ntk/nusl-233640.
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This dissertation is focused on the study of selected additives and their effect on positive and negative electrodes of Ni-Zn secondary cells. The first group of additives consists of the inorganic compounds that reduce zinc oxide solubility and thus prevents shape changes of the zinc electrode. The second group contains organic additives that have the beneficial effect of dendrite growth prevention. All additives were examined in relationship to their compatibility with the positive electrode and to their effect on the zinc electrode dendrites inhibition, hydrogen evolution and corrosion inhibition. Moreover, the study of decomposition kinetics of supersaturated zincate solution with the first group of additives was performed. Finally, a short study of pulse regime charging mode with regard to dendrites inhibition was performed and evaluated.
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Barilero, Gilles. "Etude de quelques proprietes magnetooptiques et magnetiques des semiconducteurs semimagnetiques zn : :(1-x)mn::(x)te et hg::(1-x)mn::(x)te." Paris 6, 1987. http://www.theses.fr/1987PA066084.
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L'effet d'echange entre les electrons de bande et les electrons d des ions manganese modifie les produits electroniques des alliages de zn dans un champ magnetique. L'effet zeeman de l'exciton permet de determiner la valeur des integrales d'echange de la bande de valence et de la bande de conduction dans ces composes. La presence d'interactions magnetiques entre les ions manganese est responsable des proprietes magnetiques. Les courbes d'aimantation des alliages dilues pour x5% en champ intense, a basse temperature, permettent de determiner la constante d'echange entre ions mn 1er voisins. Les alliages concentres presentent une phase de verre spin a basse temperature
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Gosso, Jean-Pierre. "Spectroscopie Raman des excitations magnétiques dans les fluorures antiferromagnétiques cobalteux purs ou desordonnés par substitution." Paris 13, 1986. http://www.theses.fr/1986PA132007.
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Description des excitations magnétiques dans k::(2) cof::(4) et rb::(2) cof::(4) par un modèle multi-excitonique construit sur un hamiltonien comprenant champ cristallin, couplage spin-orbite et échange de heisenberg opérant sur le multiplet fondamental de l'ion cobalt en champ cristallin cubique. L'interprétation pour les composés désordonnés par substitution d'un ion magnétique mn se fait par fonctions de green ou modèle de champ moléculaire
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Maury, Julien. "Nouveaux développements en chimie radicalaire des dialkylzincs : études mécanistiques et applications en synthèse." Thesis, Aix-Marseille, 2012. http://www.theses.fr/2012AIXM4351.
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Le travail présenté dans ce mémoire de thèse concerne pour l'essentiel, l'utilisation des dialkylzincs en tant que médiateurs de réactions radicalaires. La particularité de ces organométalliques réside dans le fait qu'ils sont, d'une part, de très bons précurseurs de radicaux alkyle en présence d'oxygène, et d'autre part, qu'ils peuvent subir des réactions de substitution homolytique bimoléculaire permettant de passer au cours d'une même réaction d'une espèce radicalaire à une espèce organométallique. Ainsi, les dialkylzincs sont de très bons médiateurs de réactions radicalaires et polaires en cascade en milieu aérobie.Cette méthodologie a été appliquée à la synthèse one-pot stéréosélective de γ-lactones disubstituées et de pyrrolizidines à partir du fumarate de diéthyle. La synthèse inédite de dérivés fumariques tri- et tétrasubstitués a été réalisée, à partir de l'acétylènedicarboxylate de diéthyle. Des cétoesters ont également été préparés à partir du bromoacrylate d'éthyle et de cétones silylées. L'utilisation d'azoture d'alkyle comme accepteur de radicaux s'est révélée infructueuse mais a permis de détecter une réactivité originale des azotures d'alkyle, qui en présence d'iodure de tertiobutyle, sont convertis en iodures correspondants. Enfin, une étude fondamentale par RPE du mécanisme d'oxydation des dialkylzincs a été réalisée afin de mieux appréhender les différences de comportement observées pour les divers dialkylzincs à l'échelle préparativeThe research work reported in this thesis is essentially concerned with the use of dialkylzincs in radical reactions. The peculiar behavior of these organometallic reagents resides in the fact that they are good precursors of alkyl radicals in the presence of oxygen and that they are good partners for bimolecular homolytic substitution reactions that enable to generate polar species from radical ones. Thereby, dialkylzincs are reagents of choice to perform radical-polar cascades in aerobic medium.This methodology has been applied to the one-pot stereoselective synthesis of disubstituted γ-lactones and pyrrolizidines from diethylfumarate and to the original formation of tri- and tetrasubstituted fumaric derivatives from diethylacetylene dicarboxylate. Ketoesters have also been prepared from bromoethylacrylate and sylilated ketones. The use of alkyl azide as radical acceptor in this process failed but a new reactivity of alkyl azides was detected during this study, i.e, their original conversion into the corresponding alkyl iodides in the presence of t-BuI.Finally, mechanistic studies have been achieved to investigate the mechanism of the oxidation of dialkylzincs. EPR experiments have been performed with the aim to gain a better understanding of the behavior observed for various dialkylzincs at preparative scale
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Dawood, Ihssan. "Modélisation du transfert de métaux lourds dans les sols non saturés (modèle fractionnaire hydrogéochimique)." Phd thesis, Université des Sciences et Technologie de Lille - Lille I, 2007. http://tel.archives-ouvertes.fr/tel-00422621.
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Beaucoup d'études ont montré que l'équation d'advection-dispersion classique ne permet pas de simuler correctement le transport de solutés dans les sols hétérogènes, ni de prendre en considération la spéciation des solutés dans les systèmes géochimiques que constituent les sols. Dans ce travail, un modèle fractionnaire hydrogéochimique a été proposé pour simuler le transport et la spéciation des métaux lourds dans la zone non saturée des sols, que ce soit en régime permanent ou transitoire. Ce modèle a été proposé pour remédier aux limitations du modèle classique d'advection dispersion. En régime permanent, la solution analytique de l'équation fractionnaire d'advection-dispersion a été couplée sous MATLAB au modèle de réactions géochimiques, et ce nouveau modèle a été validé à l'aide de résultats expérimentaux. En régime non permanent, une nouvelle solution numérique de l'équation fractionnaire d'advection-dispersion est proposée, et couplée avec un modèle d'écoulement et un modèle géochimique. Le modèle résultant, programmé sous MATLAB, a été testé en le comparant à des simulations obtenues avec les codes HYDRUS-1D et HP1. Les résultats de validation ont montré que le nouveau modèle fractionnaire reproduit bien le transfert de solutés dans la zone non saturée des sols et qu'il est capable de donner plus de détails sur les espèces chimiques présentes dans le sol, sur leur migration et leur interaction. Le nouveau modèle a été utilisé pour étudier le transfert de zinc dans la région de Kempen (à la frontière entre la Belgique et les Pays Bas). Il s'agit d'un site fortement pollué par les métaux lourds rejetés par les fonderies de zinc existant dans la région. Une étude paramétrique a été conduite pour déterminer la sensibilité du modèle à une variation de ses paramètres hydrologiques ou géochimiques. La conductivité hydraulique du sol (Ks), la teneur en eau à saturation (θs) et la teneur en eau initiale (θini) du sol sont les paramètres les plus influents pour le modèle d'écoulement d'eau. Le modèle fractionnaire de transport de soluté est sensible à la variation de l'ordre fractionnaire de dérivation (α) et à celle du coefficient de dispersion (D). Le pH est le facteur déterminant pour le modèle géochimique, suivi par la concentration en SO42- et en CO32-. L'effet des cations Al3+, Mn2+ et Fe2+ n'est pas significatif.
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Frenzel, Peter, Andrea Preuß, Jörn Bankwitz, Colin Georgi, Fabian Ganss, Lutz Mertens, Stefan E. Schulz, Olav Hellwig, Michael Mehring, and Heinrich Lang. "Synthesis of Mg and Zn diolates and their use in metal oxide deposition." Royal Society of Chemistry, 2019. https://monarch.qucosa.de/id/qucosa%3A33722.
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The synthesis of complexes [M(OCHMeCH2NMeCH2)2] (5, M = Mg; 7, M = Zn) is described. Treatment of MeHNCH2CH2NMeH (1) with 2-methyloxirane (2) gave diol (HOCHMeCH2NMeCH2)2 (3), which upon reaction with equimolar amounts of MR2 (4, M = Mg, R = Bu; 6, M = Zn, R = Et) gave 5 and 7. The thermal behavior and vapor pressure of 5 and 7 were investigated to show whether they are suited as CVD (= chemical vapor deposition) and/or spin-coating precursors for MgO or ZnO layer formation. Thermogravimetric (TG) studies revealed that 5 and 7 decompose between 80–530 °C forming MgO and ZnO as evidenced by PXRD studies. In addition, TG-MS-coupled experiments were carried out with 7 proving that decomposition occurs by M–O, C–O, C–N and C–C bond cleavages, as evidenced from the detection of fragments such as CH4N+, C2H4N+, C2H5N+, CH2O+, C2H2O+ and C2H3O+. The vapor pressure of 7 was measured at 10.4 mbar at 160 °C, while 5 is non-volatile. The layers obtained by CVD are dense and conformal with a somewhat granulated surface morphology as evidenced by SEM studies. In addition, spin–coating experiments using 5 and 7 as precursors were applied. The corresponding MO layer thicknesses are between 7–140 nm (CVD) or 80 nm and 65 nm (5, 7; spin-coating). EDX and XPS measurements confirm the formation of MgO and ZnO films, however, containing 12–24 mol% (CVD) or 5–9 mol% (spin-coating) carbon. GIXRD studies verify the crystalline character of the deposited layers obtained by CVD and the spin-coating processes.
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Ferrand, David. "Interactions d'échange ferromagnétiques induites par un gaz de trous dans des hétérostructures 2D et des couches 3D de semi-conducteurs II-VI." Université Joseph Fourier (Grenoble), 1999. http://www.theses.fr/1999GRE10174.
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L'electronique de spin se propose de realiser de nouveaux dispositifs bases sur le controle a la fois du spin et de la charge des porteurs. Dans ce cadre, les semiconducteurs magnetiques dilues ii-vi (cd ( 1 - x )mn xte et zn ( 1 - x )mn xte) constituent des materiaux modeles pour les etudes fondamentales avec des systemes physiques originaux comportant des spins localises couples par des interactions d'echange avec un gaz de porteurs de dimensionalite variable (3d, 2d), et avec une densite que l'on peut faire varier independamment de la concentration de spins. Ce travail est consacre a l'etude de deux types de structures, des couches epaisses 3d de zn ( 1 - x )mn xte degenerees de type p, et des heterostructures 2d constituees de puits quantiques cd ( 1 - x )mn xte dopes p par modulation de dopage. On observe dans ces deux types d'echantillons des interactions d'echange ferromagnetiques induites par le gaz de trous (temperature de curie-weiss positive), et la presence d'une phase magnetique ordonnee en dessous de la temperature de curie-weiss. Les temperatures de curie-weiss observees sont en bon accord avec la description du couplage entre les spins et le gaz de trous dans un modele de champ moyen les couches de zn ( 1 - x )mn xte ont ete caracterisees avec des mesures de transport sous champ magnetiques entre 1. 5k et 300k et des mesures d'aimantation. Les mesures de transport montrent la presence d'effets de localisation importants en dessous de 15k avec la formation de polarons magnetiques et la presence d'effet hall anormal resultant de l'effet important du couplage spin-orbite sur les trous. Les proprietes magnetiques des puits quantiques sont determinees par spectroscopie magnetooptique en champ faible. Nous avons caracterise les proprietes electroniques du gaz de trous 2d avec des mesures de transport entre 300k et 15k et par des mesures de spectroscopie magnetooptique en champ fort (0-20t) qui mettent en evidence un role important des effets excitoniques (excitons, excitons charges x+).
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(9820148), Luke Moertel. "Microarray analysis of the Schistosoma japonicum transcriptome." Thesis, 2006. https://figshare.com/articles/thesis/Microarray_analysis_of_the_Schistosoma_japonicum_transcriptome/13423745.
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Schistosomiasis, a disease of humans caused by helminth parasites of the genus Schistosoma, kills 200 to 500 thousand people annually, endangering over 600 million people world-wide with 200 million people infected in 2003 [1, 2]. Three species of schistosome are primarily responsible for human infections, namely, Schistosoma haematobium, endemic to Africa, India, and the Middle East, S. mansoni, endemic to Africa / South America, and S. japonicum endemic to China and the Philippines [3]. The major pathological effects of schistosomiasis result from the deposition of parasite ova in human tissues and the subsequent intense granulomatous response induced by these eggs. There is a high priority to provide an effective sub-unit vaccine against these schistosome flukes, using proteins encoded by cDNAs expressed by the parasites at critical phases of their development. One technique that may expedite this gene identification is the use of microarrays for expression analysis. A 22,575 feature custom oligonucleotide DNA microarray designed from public domain databases of schistosome ESTs (Expressed Sequence Tags) was used to explore differential gene expression between the Philippine (SJP) and Chinese (SJC) strains of S. japonicum, and between males and females. It was found that 593, 664 and 426 probes were differentially expressed between the two geographical strains when mix sexed adults, male worms and female worms were compared respectively. Additionally, the study revealed that 1,163 male- and 1,016 female-associated probes were differentially expressed in SJP whereas 1,047 male- and 897 female-associated probes were differentially expressed in SJC [4]. Further to this, a detailed real time PCR expression study was used to explore the differential expression of eight genes of interest throughout the SJC life cycle, which showed that several of the genes were down-regulated in different life cycle stages. The study has greatly expanded previously published data of strain and gender-associated differential expression in S. japonicum. Further, the new data will provide a stepping stone for understanding the complexities of the biology, sexual differentiation, maturation, and development of human schistosomes, signaling new approaches for identifying novel intervention and diagnostic targets against schistosomiasis [4].
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Chen, Chih-Chem, and 陳芝君. "Preparation of Zinc Oxide Films by Spin-Coating Techology." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/5zxsbe.
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碩士國立虎尾科技大學
光電與材料科技研究所在職專班
102
Zinc oxide (ZnO) thin film was prepared by spin-coating technology in this thesis. The solution composed of zinc acetate and sodium hydroxide is used as the coating, which spins on the silicon and glass substrate uniformly. The ZnO film will form on the substrate after baking in furnace or rapid thermal annealing system. The effects of zinc acetate concentration, sodium hydroxide concentration, and baking temperature were investigated in this thesis through the intensity and full width at half maximum (FWHM) of photoluminescence (PL), transmittance in visual range, atomic force microscope (AFM) images, scan electron microscope (SEM) images, and Raman scattering. The optimal concentration of zinc acetate and sodium hydroxide are 0.02M and 1M, respectively. The best baking temperature is about 200 oC under vacuum condition. The transmittance and root-mean-square (RMS) roughness of ZnO film are 90 % and 10.831nm, respectively under the optimal condition. The peak position and FWHM of PL spectrum at optimal condition are 379 nm and 20 nm, respectively. With introducing the silver nano-particles in the ZnO thin film can bring in the surface plasmon effect, which can apply to the optoelectronics to enhance the efficiency.
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Rai, Shishir K. "Zinc diffusion in GaAsSb from spin-on glass dopant sources." 2004. http://etd.nd.edu/ETD-db/theses/available/etd-12152004-143702/.
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Kao, Hsiu-Fen, and 高秀芬. "Spin-Splitting Calculation for Zinc-blende and Wurtzite Structures of III-V Semiconductors." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/01584071227955428303.
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博士國立中山大學
物理學系研究所
100
In this study, the spin-splitting energy of the lowest conduction bands in bulk zincblende and wurtzite structures of III-V semiconductors had been investigated by the linear combination of atomic orbital (LCAO) method, the atomic bond-orbital model (ABOM), and the two-band k．p (2KP) model. Spin-splitting calculation for zincblende structures: We develop a 16-band atomic bond-orbital model (ABOM) to compute the spin splitting induced by bulk inversion asymmetry in zincblende materials. This model is derived from the linear combination of atomic orbital (LCAO) scheme such that the characteristics of the real atomic orbitals can be preserved to calculate the spin splitting. The Hamiltonian of 16-band center-zone ABOM (CZABOM) is based on a similarity transformation performed on the nearest-neighbor LCAO Hamiltonian with a second-order Taylor expansion over k at the Γ point. The spin-splitting energies in bulk zincblende semiconductors, GaAs and InSb, are calculated, and the results agree with the LCAO and first-principles calculations. However, we find that the spin-orbit coupling between bonding and antibonding p-like states, evaluated by the 16CZABOM, dominates the spin splitting of the lowest conduction bands in the zincblende materials. Spin-splitting calculation for wurtzite structures: The spin-splitting energies in biaxially strained bulk wurtzite material AlN are calculated using the linear combination of atomic orbital (LCAO) method, and the equi-spin-splitting distributions in k-space near the minimum-spin-splitting (MSS) surfaces are illustrated. These data are compared with those derived analytically by two-band k．p (2KP) model. It is found that the results from these two methods are in good agreement for small k. However, the ellipsoidal MSS surface under biaxial compressive strain does not exist in the 2KP model, because the data points are far from the Γ point. Instead, three basic shapes of the MSS surface occur in the wurtzite Brillouin zone: a hyperboloid of two sheets, a hexagonal cone, and a hyperboloid of one sheet, evaluated from the LCAO method across the range of biaxial strains from compressive to tensile. The shapes of the equi-spin-splitting (ESS) surfaces near these MSS surfaces have also three types: a hyperboloid of one sheet, an approximate, asymmetric hyperboloid surface, and an opposing hyperboloid of one sheet.
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Shao-HseinLin and 林劭諴. "Study on Copper-zinc-tin-sulfur(CZTS) Thin Film Using Spin-coating Technology." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/gce98z.
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碩士國立虎尾科技大學
光電與材料科技研究所
102
There are several technologies including Electro-deposition technology, radio-frequency (RF) magnetron sputtering technology, spray pyrolysis method, co-evaporate technology, photo-chemical deposition method, and pulsed laser deposition (PLD) technology to fabricate CZTS thin film. Among these technologies, spray pyrolysis method attracts much attention due to the versatile, low cost and large area production. However, the composition of each element in CZTS thin film is difficult to control, which results the problem of reliability. In addition, in order to obtain a uniformed thin film on a heating substrate by spraying the aqueous solution, a slow deposition rate is needed. The low deposition rate brings the problem of low throughput for mass production. Based on this point of view, we proposed spin coating method to substitute spray pyrolysis technology in this proposal. We will fabricate the CZTS thin film, by versatile processes including using the different mole concentration of cupric chloride (CuCl2), zinc chloride (ZnCl2), tin chloride (SnCl2), thiourea aqueous solution to spin on the glass substrate and then heating by the furnace or rapid thermal annealing system to film growth. The optimum aqueous solution for CZTS thin film deposition will be investigated by the crystalline structure and optical characteristics.
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Wu, Kuangyu, and 吳光裕. "Study On The Characterization Of Ga-doped Zinc Oxide Thin Film By Spin-coating." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/18573260827920930640.
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碩士義守大學
材料科學與工程學系
100
With the technological progress and mature, and more on the needs of the population, the product toward the light, short, thin, small and exquisite, the direction of the power-saving effort, such new materials has become the technological development of key projects. Because zinc oxide thin film references a lot of research, but very small difference in the optical transmittance and electrical part of the ITO film properties, so the general use of zinc oxide as the transparent conductive films has been as research subjects. In this study, through the use of sol-gel method of spin-coating and prepared on glass substrates (corning 1373) to improve the conductivity of ZnO thin films by doping of gallium. By adjusting pH values, the electrical property of GZO films are improved in term of better crystallization. The experimental results showed that the best parameters of the doped gallium zinc oxide thin films at room temperature: the amount of Ga doping in 3.0at% and the pH value of 7.0, and heat treatment at 650℃, GZO film has the carrier concentration of 5.53 ×1020cm-3, the carrier mobility of 3.18 cm2 V-1 s-1, and a resistivity of 3.55× 10-3 Ω-cm. The average transmittance in the visible range is about 70%.
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Chou, Lin-Fu, and 周林甫. "Study of Zinc Diffusion In InP-based Semiconductor Using Spin-on Film and RTA Process." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/kybma2.
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碩士國立臺北科技大學
光電工程系研究所
96
The Zn diffusion using a spin-on film is a relatively simple and reproducible method for mass production of InP-base optoelectronic devices. In this study, we use ZPDC2-2000 product as diffusion source, spun on undoped n-type InP surface using a conventional photoresist spinner. After oxygen plasma treatment and deposition a Si3N4 capping layer, diffusion was performed in the rapid thermal anneal (RTA) with pure hydrogen. Finally, the wafer were annealed additionally at 600℃ for 10 sec by the same RTA system to achieve a high degree of activation. The main objective of our study is to establish an standard SOF/RTA process and obtain the parameter of zinc diffusion in InP. Thus, we investigate zinc and hole concentration profiles relying on secondary ion mass spectroscopy (SIMS) and electrochemical capacitance-voltage (EC-V) measurements. A linear increase of the depth of the p-n junction with the square root of diffusion time is observed. The diffusion coefficients of 2.22×10-11㎝2/s、14.7×10-11㎝2/s and 25.8×10-11㎝2/s have been calculated respectively at three different temperatures (535, 550, and 575℃). A higher hole concentration (≧3×1018cm-3) can be achieved and a steeper front of p-n junction can be formed by SOF/RTA diffusion. With additional annealing the electrical activity of zinc can be increased significantly with a nearly unchanged depth of p-n junction. More than 80％ of all zinc atoms are electrically active in the annealed sample. The activation energy for diffusion of Zn into InP is 1.47eV in this SOF/RTA method.
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CHEN, CHIAN-YOU, and 陳芊酉. "Synthesis of Zinc Oxide Nanostructures on Porous Silicon and Meta Substrates by Electroplating and Spin Coating Methods." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/ppzjgr.
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碩士國立暨南國際大學
應用材料及光電工程學系
105
In this thesis, ZnO nanostructures were deposited on metal-coated porous silicon substrates. The coated metal consisting including silver (Ag) film and gold (Au) film was deposited by E-Gun System on porous silicon (PS) substrates. Then, ZnO NRs were grown on the substrate by electrochemical and spin coating methods. In addition to metal coating, to vary the characteristics of the nanocomposites, graphene was also incorporated in the fabrication process. ZnO/graphene hybrids were deposited on the PS substrates. These nanostructures were characterized by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Atomic Force Microscope, Photoluminescence emission spectroscopy. However, growing ZnO nanostructures by spin coating methods showed better crystallinity. Moreover, compared with graphene/ZnO and.ZnO–graphene hybrids, PL spectra revealed higher intensity of defect luminescence for ZnO–graphene hybrid nanostructures which could be due to mixture in ZnO. Furthermore, ZnO–graphene hybrids had better antibacterial behavior than those ZnO/graphene structures. The structure design is promising for future applications of semiconductor and metal coupling to form highly efficient optoelectronic devices and biosensors.
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"Synthesis and Characterization of Nanocrystalline Nickel-Zinc Spinel Ferrite Thin Films Using the Spin-Spray Deposition Method." Doctoral diss., 2013. http://hdl.handle.net/2286/R.I.17906.
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abstract: The overall objective of this project is to optimize the development of magnetic ferrite thin films targeted for enabling low-loss broadband communication devices, miniaturized low-microwave inductors and electromagnetic noise suppressors. The focus of this objective is to design and build a reactor and improve the spin-spray process. Each film is then characterized and optimized to have a high permeability and high frequency in the range of 500 MHz - 3 GHz. Films produced by the µ-droplet deposition regime yields a higher Snoek's product than the continuous liquid layer regime. The highest Snoek's product occurs when it is deposited at an oxidant pH of 8.28. The Ni-Zn-Co ferrite magnetic domains were imaged using the Lorentz TEM in which multi-grain domains are experimentally observed for the first time.Dissertation/Thesis
Ph.D. Materials Science and Engineering 2013
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MacDonald, Daniel. "1,2,3-Dithiazolyl and 1,2,3,5-Dithiadiazolyl Radicals as Spin-Bearing Ligands Towards the Design of New Molecular Materials." Thesis, 2012. http://hdl.handle.net/10214/4000.
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A series of binuclear coordination complexes of 4-(2′-pyrimidal)-1,2,3,5-dithiadiazolyl and its selenium analogue have been prepared to examine their structural and magnetic properties. The zinc(II) coordination complex is the first example of a DTDA radical ligand N-coordinated to a diamagnetic metal center. The magnetic properties reveal that it exhibits Curie behaviour and can be used as a benchmark to compare the analogous coordination complexes which possess paramagnetic metal ions. The nickel(II) coordination complex of the selenium containing radical pymDSDA was shown to dimerize in the solid state and is the only binuclear complex thus far that has done so. The manganese(II) complex of pymDSDA is by far the most interesting and is isomorphous to the DTDA analogue. For both complexes, one of the two molecules in the asymmetric unit form chains in the solid state joined by intermolecular contacts between a sulfur or selenium atom from the radical, and an oxygen atom coordinated to a neighbouring molecule. This feature gives rise to a ground state spin greater than that of an individual binuclear coordination complex. The radical ligand is however disordered in the solid state and so these random chain lengths are dependent on the orientation of the ligands in adjacent complexes.
The 1,2,3-DTA species examined herein are related to the 4,5-dioxo-4,5-dihydronaphtho[1,2-d][1,2,3]dithiazolyl radical and the related protonated species 4-hydroxy-5H-naphtho[1,2-d][1,2,3]dithiazol-5-one. The proton from this latter compound has shown that it can be substituted with alkyl groups and this was achieved using acetyl chloride to place an acetyl group in this position. The above radical did not exhibit the strong donor properties required for metal coordination and preliminary investigations of the radical dianionic suggest that it is chemically irreversible by cyclic voltametry. The acetyl group unfortunately did not provide the chemically reversibility of interest although has established a potential route toward the substitution chemistry of this compound. The other 1,2,3-DTA compounds discussed herein are not complete, although the data acquired on the precursor compounds leading up to the radical will be discussed.
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LI, YI-CHUN, and 李益竣. "The zinc oxide nanorod seed layer was developed at low temperature of gallium nitride light-emitting diodes by dip coating / spin coating." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/29011231198415822746.
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碩士南臺科技大學
光電工程系
105
Light Emitting Diode is the trend of future lighting, high-power LED in the technical breakthroughs, but to completely replace the traditional lighting source, at this stage of the lighting efficiency is slightly inadequate, so that the LED can not replace the traditional lighting source, so LED luminous efficiency Promotion, is one of the keys to the current technological development. In this paper, we focus on improving the efficiency of light extraction of LED to reduce the internal total reflection of the grains as the theoretical basis to achieve the efficiency of LED light extraction. In this study, a nanostructure array was used to achieve the opportunity to reduce the total light reflection. The ZnO seed layer was grown on P-type gallium nitride by spin coating and dip coating. Then, Into the solution to growing the ZnO nanorod. In the experiment, zinc nitrate Zn (NO3) 2 / HMTA was changed at a fixed concentration, oven temperature and time, and then exposed to different temperature and time using a field emission electron microscope (FE-SEM) The Photoluminescence Spectroscopy (PL) was used to measure the light intensity, and the crystal quality was analyzed by X-ray wide-angle diffractometer. The results of the final measurement showed that the parameters of the ZnO nanorod were the best light intensity in the PL, the reaction time was 1 hour and the oven temperature was 80°C. Compared with the unstructured luminescence intensity of the grown nanorod, the highest excitation wavelengths are obtained at 516nm. Therefore, the P-type GaN diodes are grown with this parameter as the column on the surface, The current injection was measured by integrating the ball and found that the growth of the ZnO nanorod GaN diodes was increased by 0.022 V compared to the non-grown nanorod starting voltage at 5 mA current injection 150mA voltage and 0.201V increase compared with the non-grown nanorod LED, 15% increase in the light intensity part and the light emission wavelength of the two elements will be blue with the increase of the injection current caused by the phenomenon, containing ZnO nanorod The blue shift of the bipolar body is smaller than that of the conventional GaN diodes.
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Chen, Yi-Ren, and 陳奕任. "Growth of Silver-nanoparticle-distributed Zinc Oxide Thin Films to Improve The Efficiency of III-V(InGaP/GaAs/Ge) Solar Cells Using Spin-coating Technology." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/92g2gz.
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碩士國立虎尾科技大學
光電與材料科技研究所
102
ilver-nanoparticle-distributed Zinc Oxide (Ag/ZnO) thin films was prepared by spin-coating technology in this thesis. The solution composed of zinc acetate, sodium hydroxide and silver nitrate is used as the coating, which spins on the silicon and glass substrate uniformly. The Ag/ZnO films will form on the substrate after baking in furnace system. The effects of zinc acetate concentration, sodium hydroxide concentration, silver nitrate concentration were investigated in this thesis.The optimal concentration of zinc acetate and sodium hydroxide and silver nitrate concentration are 0.007M and 1 M and 0.008M, respectively. The best baking temperature is about 200 oC under vacuum condition. The Transmittance and Reflectivity of Ag/ZnO film are 95 % and 2.5% , respectively under the optimal condition. The peak position of PL spectrum at optimal condition are 379 nm and 550 nm, respectively. We will coat the bestest Ag/ZnO film on the surface of III-V(InGaP/GaAs/Ge) solar cells,it can increases the efficiency of III-V solar cells from 30.4% to 34.1%.
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Srinivasan, Dheepa. "Growth Morphology And Coarsening Of Metastable Al3Zr In Melt Spun Al-Ni-Zr Alloys." Thesis, 1996. http://etd.iisc.ernet.in/handle/2005/1950.
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Rodrigues, Catarina Martins. "Spray coating of oxide and chalcogenide semiconductor layers for TFT application." Master's thesis, 2015. http://hdl.handle.net/10362/16389.
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This work documents the deposition and optimization of semiconductor thin films using chemical spray coating technique (CSC) for application on thin-film transistors (TFTs), with a low-cost, simple method. CSC setup was implemented and explored for industrial application, within Holst Centre, an R&D center in the Netherlands. As zinc oxide had already been studied within the organization, it was used as a standard material in the initial experiments, obtaining typical mobility values of 0.14 cm2/(V.s) for unpatterned TFTs. Then, oxide X layer characteristics were compared for films deposited with CSC at 40°C and spin-coating. The mobility of the spin-coated TFTs was 103 cm2/(V.s) higher, presumably due to the lack of uniformity of spray-coated film at such low temperatures. Lastly, tin sulfide, a relatively unexplored material, was deposited by CSC in order to obtain functional TFTs and explore the device’s potential for working as a phototransistor. Despite the low mobilities of the devices, a sensitive photodetector was made, showing drain current variation of nearly one order of magnitude under yellow light. CSC technique’s simplicity and versatility was confirmed, as three different semiconductors were successfully implemented into functional devices.
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Lefevre, Bruno. "Corrosion des aciers revetus de zinc dans les zones confinées des carrosseries automobiles." Phd thesis, 2004. http://pastel.archives-ouvertes.fr/pastel-00002339.
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La corrosion automobile peut être classée en deux catégories: la corrosion cosmétique et la corrosion perforante. La corrosion cosmétique touche à l'aspect extérieur du véhicule, tandis que la corrosion perforante se produit lorsque de l'eau pénètre dans les corps creux du véhicule. Ce type de corrosion est particulièrement pernicieux puisqu'il aboutit à la perforation des tôles. L'objectif de ce travail est de comprendre les mécanismes régissant la corrosion perforante. Une cellule de corrosion a été développée afin de reproduire en laboratoire les conditions d'apparition de ce type de corrosion et permettre des mesures locales de pH dans un accostage. Le séchage des accostages et le développement de la corrosion ont été suivis par vidéo dans une enceinte climatique, les surfaces ont été caractérisées par XPS, IRRAS et MEB. Une enceinte couplée à un spectromètre PM-IRRAS a été développée pour suivre in situ la cinétique d'apparition des produits de corrosion du zinc en milieu humide.
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Garnier, Jérôme. "Elaboration de couches minces d'oxydes transparents et conducteurs par spray cvd assiste par radiation infrarouge pour applications photovoltaÏques." Phd thesis, 2009. http://pastel.archives-ouvertes.fr/pastel-00005629.
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Les oxydes métalliques sont des matériaux pouvant présenter la double propriété d'avoir une haute conductivité électrique et une bonne transparence dans le domaine du visible. Ils sont appelés « oxydes transparents et conducteurs », TCO. Le plus utilisé de ces matériaux est l'oxyde d'indium dopé étain (ITO). L'indium est un élément rare et cher qui avec la demande croissante de l'industrie des écrans plats en ITO, a vu son prix s'envoler. De nombreuses recherches sont basées sur le besoin de trouver un challenger. Des candidats tels que l'oxyde de zinc ou l'oxyde d'étain s'avèrent prometteurs. Pour déposer ces matériaux en couches minces, différentes techniques peuvent être utilisées. Nous avons choisi une technique appelée Spray-CVD car elle présente l'avantage d'avoir des dépôts de qualités avec la réaction de CVD et la facilité de manipulation des précurseurs avec le spray. Pour résumer, c'est une technique simple et économique. La particularité de cette étude est l'utilisation de lampes infrarouges comme chauffage de notre système. L'association de la technique de Spray-CVD et des lampes infrarouges est unique à notre connaissance. Nous avons appelé l'ensemble : IRASCVD (InfraRed Assisted Spray Chemical Vapor Deposition). Afin de déposer des couches compétitives de TCO avec notre technique, deux stratégies ont été déployées. La première consiste à la réalisation d'un réacteur expérimental de Spray-CVD au sein de notre laboratoire. Des films minces d'oxyde d'étain non dopé et dopé au fluor ont été étudiés ainsi que l'optimisation des paramètres de dépôts. Ces couches ont enfin été utilisées en tant qu'électrodes transparentes pour cellules solaires organiques. L'ensemble de cette étude a permis de valider les dépôts de TCO par IRASCVD. La deuxième partie de l'étude consiste à l'utilisation d'un réacteur R&D basé sur le même principe de Spray-CVD. Ce réacteur a permis le dépôt de films minces d'oxyde de zinc non dopé et dopé aluminium. Une attention particulière a été portée à l'influence des infrarouges sur les propriétés des TCO. Ces dépôts ont été comparés avec ceux réalisés avec un chauffage classique. Cette étude souligne l'impact des infrarouges sur les films minces de TCO.