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1
Hayashi, Hiroyuki. "Structure and Magnetism of Mn-doped γ-Ga2O3." 京都大学 (Kyoto University), 2010. http://hdl.handle.net/2433/120813.
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Martel, Guillermo Guzman. "Espectroscopia de absorção e emissão de CN- em KCl." Universidade de São Paulo, 1986. http://www.teses.usp.br/teses/disponiveis/54/54132/tde-14112014-103422/.
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Neste trabalho foram estudados alguns aspectos de espectroscopia de absorção e emissão de CN- em KCl. As amostras são de duas procedências: 1) Amostras de KCl + 1 mol % KCN com grau de ultra-alta pureza da Universidade de Utah. 2) Amostras de KCl + 1 mol % KCN com pequenas concentrações de OCN- introduzidas despropositadamente no crescimento. Foram comparados os resultados destas amostras. Os resultados do dicroísmo induzido mostram que nesta concentração de 1%, as moléculas de CN- tem posição de mínimo na direção [111], confirmando o modelo de dipolos [111] para concentrações menores. Um dos resultados mais interessantes é que foi observada a emissão vibracional CN- mesmo nas amostras que continham pequenas concentrações de OCN- (∼ 10-2 mol %) e que antes era considerado como inibidor da fluorescência. A emissão vibracional foi obtida pela excitação induzida do CN- acoplado com o centro F, usando a linha 514nm de um laser de Ar+ para excitar o centro F e observando a fluorescência vibracional do CN- em 4,8 μm. Também é mostrado o estudo do comportamento da fluorescência do CN- em várias concentrações de centro FIn this work were studied some aspects of absorption and emission spectroscopy of KCl: CN- single crystals. Samples were taken from two sources: High purity grade of KCl + 1 % KCN from University of Utah. Pro analysis grade of KCl + 1% KCN from IFQSC-USP which have some NCO- molecules introduced unpurposely during the growth. The results due to both types of samples are compared. The induced dicroism under uniaxial stress show that even under this 1% concentration, the CN- reorient in a [111] multiwall potential, confirming the [111] elastic dipole model for much lower concentration. One of the most interesting results is that we got CN- vibrational emission even under small concentrations of NCO- (∼ 10-2 mol %) which was first consider as fluorescence inhibitor. The vibrational emission was obtained by induced excitation of CN- coupled with F center, so we used the 514nm line of an Ar+ laser to excite the F center and observe the vibrational fluorescence of the CN- at 4,8 μm. Also we show a study of the fluorescence behavior under different F center concentrations
3
Walsh, Michael C. "Giant magnetoresistance in bismuth doped La-Ca-Mn-O perovskites." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq24937.pdf.
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Mandal, Saptarshi. "Study of Mn doped HfO2 based Synaptic Devices for Neuromorphic Applications." University of Toledo / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1384535471.
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Ruggiero, Lígia de Oliveira. "Produção e caracterização de filmes de KCl e KBr impurificados com íons Cu+." Universidade de São Paulo, 1994. http://www.teses.usp.br/teses/disponiveis/76/76132/tde-21022014-161602/.
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Através do processo de evaporação térmica é possível produzir filmes de KCl e KBr altamente dopados com íons Cu+. Investigamos o efeito de altas concentrações de Cu+ (1020 - 1021 cm -3) nestes filmes policristalinos, onde, associado com o efeito fora de centro do Cu+, origina uma forte banda de absorção propícia para aplicação ótica destes filmes como filtros passa banda na região do UV. Os filmes estudados, de 1 UM, foram preparados por coevaporação resistiva de KCl (Br), como hospedeiro, com 1 a 10% de CuCl(Br), como dopante, sobre diferentes substratos. Diversas técnicas foram usadas para obter as propriedades estrutural e ótica, tais como: microscopia eletrônica de varredura (MEV), difração de raios-X, elipsometria, absorção ótica e transmitância. Do estudo da morfologia é observado um aumento na densidade dos grãos com a concentração nominal de Cu+ de até 1021 átomos/cm-3. Este comportamento também resulta em um aumento na transmitância na região do visível. A banda de absorção em 266 nm (278 nm) para KCl ()KBr): Cu+ é atribuída à transição eletrônica parcialmente permitida de 3d10 3d94s e sua área integrada em função da temperatura mostra o comportamento da força do oscilador com a temperatura, que é propriedade do efeito fora de centro. A este efeito fora de centro está associado um dipolo elétrico devido ao deslocamento da carga da posição substitucional. Para verificar a existência de um sistema de relaxação dipolar elétrica, usamos o método de Corrente de Despolarização Termicamente Estimulada (CDTE). As medidas de CDTE mostram uma fraca e alargada banda em 49K, com energia de ativação média de 147 meV e um fator pré-exponencial de 2x10-14 seg, para amostras de KCl + 1% CuCl, com 3 UM de espessura. Nossos resultados são discutidos e comparados com outros observados em monocristais do mesmo materialThrough the thermal evaporation procedure it is possible to obtain highly Cu+ doped KCl and KBr films. We have investigated the effect of 1020 - 1021 cm-3 Cu
6
Al-Ahmadi, Noorah Ahmed. "Investigation of the electrical properties of III-V semiconductor doped with Mn." Thesis, University of Nottingham, 2011. http://eprints.nottingham.ac.uk/28686/.
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III-V semiconductors doped with Mn atoms have been studied recently for their potential applications in spintronic devices. These materials are referred to as diluted magnetic semiconductors (DMS) or ferromagnetic semiconductors. The lattice of these materials has Mn atoms (transition metal) and due to their half filled shell carries a spin and also donates carriers, "p-type" in case of Mn doping to the semiconductor lattice. Ferromagnetism is mediated by exchange interactions between localized d electrons and p-type carriers. A high transition temperature (in fact above room temperature) called Curie point, is necessary for these materials to have a practical value. The transition temperature Tc depends on the densities of both Mn impurity and the resultant hole concentration. A low density of defects, a high crystal quality and a high concentration of Mn atoms are desirable to achieve a high Tc. Additionally, cubic (zinc blende) structure offers several advantages over the hexagonal structure normally obtained for III-V semiconductors e.g. a higher crystal symmetry, smaller effective masses, higher carrier mobility, and significantly a higher doping density-which is expected to give a higher value of Tc. Both GaMnAs and GaMnN have been the materials of choice and have been studied intensely. The problems however, are related to fabricated technique, crystal quality and achieving a high doping concentration. The materials exhibit a solubility limit beyond which doping concentration are difficult to achieve. This thesis describes the investigation of the electronic properties of the zinc blend GaMnAs and GaMnN films grown at low temperature by molecular beam epitaxy (MBE) for varies concentration of Mn doping over the temperature range 15-400 K. Metal/c-GaAs: Mn/c-GaAs:Si p n junctions were studied by the I-V, C-V and C-F methods over the temperature range 15-400 K. It was found that I-V-T data could be interpreted on the basis of a back to back diode model. The c-GaAs:Mn made a Schottky contact with the metal and a p n junction with c-GaAs:Si. It was found that for the forward bias, where metal was biased negative with respect to the GaAs:Mn, the 1- v -T data could also be analysed on the basis of a Schottky behaviour. Here ideality factor n increased and the barrier height Φb decreased with temperature. This was seen to be a consequence of TFE through the metal/GaAs barrier. This was borne out by the Richardson's plots [ln (ls/T2) versus 103/nT] which exhibited straight lines. The slope indicated the barrier heights, which ranged between 1.1-1.4 eV. The backward diode on the other hand gave a barrier height of 1.4 eV, which was compatible with the proposed model. C-V-T measurements could also be accounted for, at least qualitatively, on the basis of the proposed back to back diode model. The device structure of c-GaMnN was planar. Both the Ohmic and Schottky contact were in the same plane on the top surface. I-V measurements were performed over the temperature range 100-480 K. I-V-T was explained in the terms of the Schottky model. The current was limited, however, by the Poole-Frenkel type centres in the bulk which behaved as an insulator (high resistivity semiconductor). The C-V–T was satisfactorily accounted for on the basis of MIS/MOS model. Low temperature grown films had poor material quality which made any correlation between samples difficult.
7
Pandey, Sudip. "MAGNETIC, TRANSPORT, AND MAGNETOCALORIC PROPERTIES OF BORON DOPED Ni-Mn-In ALLOYS." OpenSIUC, 2015. https://opensiuc.lib.siu.edu/theses/1754.
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The impact of B substitution in Ni50Mn35In15-xBx Heusler alloys with x = (0, 0.5, 0.75, 1, 1.1 1.5, and 2) on the structural, magnetic, transport, and parameters of magnetocaloric effect has been studied by means of room temperature XRD-diffraction, differential scanning calorimetry (DSC), and thermomagnetic measurements (in a magnetic field up to 5 T and temperature interval 5-400 K). Direct adiabatic temperature (ΔTAD) measurements have been carried out for an applied magnetic field change (ΔH) of 1.8 T. The partial substitution of In by B in Ni50Mn35In15-xBx Heusler alloys induced a non-linear temperature shift of the magnetostructural transition while Curie temperature (TC) was found to be nearly constant (TC ~ 320 K) for all compounds. The transition temperatures (T-x) phase diagram has been constructed for H = 0.005 T. The MCE parameters were found to be larger or comparable to parameters observed in other MCE materials, such as Ni50Mn34.8In14.2B and Ni50Mn35In14X (X=In, Al, and Ge) Heusler alloys. It has been demonstrated that the martensitic transformation temperature and the corresponding ∆SM can be tuned through a slight variation in composition of B in NiMnInB alloys. A magnetoresistance associated with martensitic transformation was found to be -60% for x = 0.75 at T = 240 K for a magnetic field change of 5 T. The maximum absolute value of ΔTAD = 2.5 K was observed at the magnetostructural transition for Ni50Mn35In14.5B0.5. The roles of the magnetic and structural changes on the transition temperatures are discussed.
8
Long, Phan The. "Synthesis and characterization of Mn-Doped ZnO sprintronic materials: Polycrystalline ceramics, thin films, and nanostructures." Thesis, University of Bristol, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.492507.
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Recent theoretical calculations have predicted that ZnO doped with Mn exhibits room-temperature ferromagnetism. This has attracted intensive interest, because of its prospective applications in spintronic devices. However, experimental studies on Mndoped ZnO materials have revealed that their magnetic properties vary from the ferromagnetic through antiferromagnetic and spin-glass to the paramagnetic. This makes the question of the origin of ferromagnetism in Mn-ZnO materials become more complicated.
9
Liu, Zhongsheng. "Magnetic MAX phases: Itinerant electron magnetism of pure and Mn-doped Cr-based MAX phases." 京都大学 (Kyoto University), 2015. http://hdl.handle.net/2433/199312.
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Tsai, Yi-Lin. "Phase relationships and electrical properties of undoped and Mn-doped ACu₃(Ti,Nb,Ta)₄O₁₂ perovskites." Thesis, University of Sheffield, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.537998.
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Rancati, Andrea. "Ab initio simulations of topological phase transitions in Dirac semimetal Cd3As2 doped with Zn and Mn impurities." Thesis, Linnéuniversitetet, Institutionen för fysik och elektroteknik (IFE), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-80767.
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In this work we exploit the unique characteristics of a Dirac semimetal material to be symmetry-protected, to investigate dierent topological phase transitions provided by chemical dopings, focusing in particular on the electronic, magnetic and topological properties of the doped systems, studied by the mean of rst-principles methods based on density functional theory (DFT) approach. In particular these doped systems, besides being of interest for investigating the role of topology in solid state physics, could have a great potential for practical application since the dierent topological phases that come along with the chemical dopings allow one to exploit the unique properties of topological materials. The starting point for our study will be the material called cadmium-arsenide (Cd3As2), an example of a topological Dirac semimetal, which is chemically stable at ambient conditions. Chapter I presents a general introduction to topology, especially in condensed matter physics, and to the main physical properties of the topological materials we mentioned. Then, in chapter II, we briey present the methods and the computational tools that we used for our study. In chapter III a more detailed introduction to our work is given, along with a schemetic view of the path we followed, together with the results that we obtained for pristine Cd3As2, which we use as bench mark for our computational methods. Finally, in chapter IV and V, the results for the doped systems are presented and discussed, respectevely for the non-magnetic (IV) and magnetic (V) dopings. Our study has enabled us to discern how doping can give rise to see dierent topological phase transitions. Specically our work shows that dierent realizations of non-magnetic doping gives rise to dierent topological phases: the topological Weyl semimetal phase, which is of great interest since it can support a robust quantum spin Hall eect, and a very special mixed Dirac + Weyl phase, where surprisingly both a Dirac and a Weyl phase can coexist in the same system. Furthermore, magnetically doped systems show the emergence of a magnetic Weyl phase, which can support a quantum anomalous Hall eect. Our work can be the starting point for future studies, both theoretical and experimental, in which the unique physical properties we found in the doped Cd3As2 systems can be further investigated, in order to exploit them for practical applications.
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Herwadkar, Aditi A. "Electronic structure and magnetism in some transition metal nitrides Mn-doped ScN, dilute magnetic semiconductor and CrN, Mott insulator /." online version, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=case1164816868.
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Norman, Thaddeus Jude. "Optical and structural properties of gold nanoparticle aggregates and Mn 2+, CU 2+, and Ag 1+ doped ZnSe nanoparticles /." Diss., Digital Dissertations Database. Restricted to UC campuses, 2004. http://uclibs.org/PID/11984.
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Herwadkar, Aditi Dr. "Electronic structure and magnetism in some transition metal nitrides: MN-doped ScN, dilute magnetic semiconductor and CrN, Mott insulator." Case Western Reserve University School of Graduate Studies / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=case1164816868.
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Kanazawa, Hideki. "Synthesis of large single crystals of pure forsterite and Fe, Mn and Cr doped forsterites, and their optical properties." Kyoto University, 2007. http://hdl.handle.net/2433/136428.
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Kyoto University (京都大学)0048
新制・課程博士
博士(人間・環境学)
甲第13155号
人博第362号
新制||人||89(附属図書館)
18||D||163(吉田南総合図書館)
UT51-2007-H428
京都大学大学院人間・環境学研究科相関環境学
(主査)教授 玉田 攻, 助教授 田部 勢津久, 助教授 石川 尚人
学位規則第4条第1項該当
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Zeng, Li. "Disordered electronic and magnetic systems - transition metal (Mn) and rare earth (Gd) doped amorphous group IV semiconductors (C, Si, Ge)." Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2007. http://wwwlib.umi.com/cr/ucsd/fullcit?p3284117.
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Thesis (Ph. D.)--University of California, San Diego, 2007.Title from first page of PDF file (viewed January 9, 2008). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 123-132).
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Ahmed, Mustafa M. Abdalla. "Alternating-Current Thin-Film Electroluminescent Device Characterization." Doctoral thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2008. http://www.nusl.cz/ntk/nusl-233432.
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Jádrem této disertační práce bylo studovat optické a elektrické charakteristiky tenkovrstvých elektroluminiscenčních součástek řízených střídavým proudem (ACTFEL) a zejména vliv procesu stárnutí luminiforů na jejich optické a elektrické vlastnosti. Cílem této studie měl být příspěvek ke zvýšení celkové účinnosti luminoforů, vyjádřené pomocí jasu, účinnosti a stability. Vzhledem k tomu, že současnou dominantní technologií plochých obrazovek je LCD, musí se další alternativní technologie plošných displejů porovnávat s LCD. Výhodou ACTFEL displejů proti LCD je lepší rozlišení, větší teplotní rozsah činnosti, větší čtecí úhel, či možnost čtení při mnohem vyšší intenzitě pozadí. Na druhou stranu je jejich nevýhodou vyšší energetická náročnost, problém s odpovídající barevností tří základních barev a podstatně vyšší napětí nutné pro činnost displeje. K dosažení tohoto cíle jsme provedli optická, elektrická a optoelektrická měření ACTFEL struktur a ZnS:Mn luminoforů. Navíc jsme studovali vliv dotování vrstvy pomocí KCl na chování mikrostruktury a na elektroluminiscenční vlastnosti (zejména na jas a světelnou účinnost) ZnS:Mn luminoforů. Provedli jsme i některá, ne zcela obvyklá, měření ACTFEL součástek. Vypočítali jsme i rozptylový poměr nabitých barevných center a simulovali transportní charakteristiky v ACTFEL součástkách. Studovali jsme vliv stárnutí dvou typů ZnS:Mn luminoforů (s vrstvou napařenou či získanou pomocí epitaxe atomových vrstev) monitorováním závislostí svítivost-napětí (L-V), velikost vnitřního náboje - elektrické pole luminoforu (Q-Fp) a kapacitance-napětí (C-V) ve zvolených časových intervalech v průběhu stárnutí. Provedli jsme krátkodobá i dlouhodobá měření a pokusili jsme se i o vizualizaci struktury luminoforu se subvlnovým rozlišením pomocí optického rastrovacího mikroskopu pracujícího v blízkém poli (SNOM). Na praktickém případu zeleného Zn2GeO4:Mn (2% Mn) ACTFEL displeje, pracujícího při 50 Hz, jsme také studovali stabilitu svítivosti pomocí měření závislosti svítivosti na napětí (L-V) a světelné účinnosti na napětí (eta-V). Přitom byl zhodnocen význam těchto charakteristik. Nezanedbatelnou a neoddělitelnou součástí této práce je i její pedagogický aspekt. Předložený text by mohl být využit i jako učebnice pro studenty na mé univerzitě v Lybii.
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Mathabathe, Maria Ntsoaki. "The development and microstructural evolution of the bulk yTi-45Al-2Nb (Sn Cr Mn & Si)-doped intermetallic alloys and their mechanical properties." Thesis, University of Pretoria, 2019. http://hdl.handle.net/2263/77843.
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The -TiAl based intermetallic alloys play an important role in structural applications, such as
aerospace and automotive industries. The current work studied the novel development and
microstructural evolution, along with their mechanical properties of the -TiAl based alloys viz.
the binary (Ti--48Al), ternary (Ti--48Al-2Nb), quaternary (Ti--48Al-2Nb-0.7Cr) and quinary (Ti-
-48Al-2Nb-0.7Cr-0.3Si). The alloys were fabricated employing both powder and ingot
metallurgy routes. Consolidation of the alloys was achieved by vacuum arc melting. As-cast and
thermally treated sections of sample ingots were characterized using optical microscopy (OM) and
scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photo-electron spectroscopy
(XPS), atomic force microscopy (AFM), Raman spectroscopy (RS), transmission electron
microscopy (TEM), electron backscattered diffraction (EBSD). Thermal analysis, such as
differential scanning calorimetry (DSC) and differential thermal analysis (DTA) were
employed in order to give insight into phase transformations. Moreover, hardness, room temperature
tensile testing with subsequent fractography, cyclic oxidation, nitriding treatment and
incorporating first principle calculations with orientation relationships were some of the property
behaviors studied in the dissertation.
The key findings of the research were: 1) the addition of Nb and Cr to the -TiAl based alloys
promoted grain refinement and induced phase transformation, 2) slight overall Al loss of the
-TiAl based alloys was observed due to the compaction method prior to melting. Uni-axial cold
pressing of the blended metal powders indicated that Al particles migrated to the surface in
contact with the die facets, 3) of all the alloys studied, the quinary (Ti-48Al-2Nb-0.7Cr-0.3Si)
alloy exhibited good mechanical properties, 4) phase transformation and microstructural
evolution of an α-solidifying quinary alloy illustrated a homogeneous microstructure with
Spheriodized/Widmanstätten laths, 5) it has been shown that the formation of /α2/Ti5Si3 in the
Ti-48Al-2Nb-0.7Cr-0.3Si intermetallic alloy followed the Blackburn orientation relationship of both
the as-cast (-solidifying) and heat-treated (α-solidifying) phases, 6) surface cladding in a N/Ar
atmosphere indicated that the oxidation properties of the ternary and quinary showed improved
significance compared to the binary and quaternary alloys and, 7) Sn and Mn, were some of the
doping elements added to the quinary alloy excluding the Cr due to its inducement of the brittle
β-phase which exhibits low mechanical properties. As a result, -TiAl based Ti- 48Al-2Nb-0.3Si,
Ti-48Al-2Nb-1Sn-0.3Si, and Ti-48Al-2Nb-1Sn-0.7Mn-0.3Si intermetallic
alloys were developed and investigated.Thesis (PhD)--University of Pretoria, 2019.
Materials Science and Metallurgical Engineering
PhD
Unrestricted
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CORDEIRO, MOACIR R. "Investigação de interações hiperfinas em Zn(1-x)MT(x)O, onde MT=(V, Cr, Mn, Fe, Co, Ni, Cu) pela técnica de correlação angular gama-gama perturbada." reponame:Repositório Institucional do IPEN, 2012. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10073.
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Made available in DSpace on 2014-10-09T12:34:26Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T14:09:48Z (GMT). No. of bitstreams: 0
Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Weng, Huan-chung, and 翁煥忠. "Phase transition of the Mn-doped and Co-doped zinc oxide." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/52587841640794165762.
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碩士國立臺南大學
自然科學教育學系碩士班
92
ABSTRACT Because the optics component with short-wavelength and the electronic element demands of high-energy , high frequency increase in recent years, which make wide band gap semiconductor extensive study and application . Zinc oxide belong to wide band gap (3.4 eV ) too, because its wide band gap, transparent and fabrication improve, Zinc oxide is also cause the agitation of studying gradually. Zinc oxide the most interesting place of pure zinc oxide has no phase transition , but it has phase transition (mostly in the adjacent place of the room temperature) with doping impurities , at the same time it''s physical properties change for different doping impurities. One of the method was doping impurities in materials which we were known and using. It could change the characteristic and the structure of the original. In this study we analyze the characteristic that zinc oxide was doped impurities with different concentration by X-Ray,Raman,DSC and SEM. We study the relationship between the transition temperature and the concentration of doped impurities. When the doping amount of the manganese, is more that 5% the phase transition, just happen. When the doping amount of the cobalt , the transition temperature increase as the doping amount of cobalt increase under 10%. The other hand the transition temperature decrease as the doping amount of cobalt increase up 10%. Though doping manganese and cobalt will change phase transition temperature of zinc oxide, but the mechanism of phase transition need to study.
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Chen, Wei-Hao, and 陳韋豪. "Photoelectric characteristics of Mn-doped ZnO nanowires." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/61749312655110764382.
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碩士國立中興大學
物理學系所
101
Zinc oxide is a semiconductor material with widely applications. It has extremely large direct binding energy and exciton energy (about 60 meV) at room temperture allowance the formation of stable exciton in ZnO at room temperature and thus ZnO has significant advantages in optoelectronic applications such as ultraviolet sensor. In this study, High density Mn-doped ZnO nanowires arrays were fabricated via low temperature hydrothermal at 90°C for 3 hour. The structure and magnetism of the nanowires have been examined. The results of photo-luminescent (PL) and absorption spectrum showed that Mn-doped ZnO emission peak will blue shift. X-ray diffraction (XRD) and transmission electron microscope (TEM) demonstrate that Mn was successfully doped into the nanowires and nanowires were single-crystal grown along the (002) direction. Raman spectrum demonstrate Mn dopeing in the form of ZnO nanowires Besides, ZnO nanowires were used to manufacture single-nanowire-devices by focus ion beam (FIB). Upon the illumination by a ultra-violet light (365nm), photoelectric properties and UV responding properties were compared. Nanowire sensors have shorter response time and recovery times than nanowires array sensors. Mn doped ZnO can effective increase the ratio of current variation.
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Deng, Ming Cheng, and 鄧明正. "Mn-,Co- Doped Maghemite and Magnetite Particles." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/39902754094986520939.
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Han, Jiaping. "Sintering and electrical properties of Mn-doped and Al-doped ZnO ceramics." Master's thesis, 2001. http://hdl.handle.net/10773/24986.
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ZnO based materials have attracted much attention both in science and in technology,
due to their rich properties and wide applications. The study of the
sintering and electrical properties of ZnO based materials is important for their
applications, such as the varistor application. The present work is concerned
with the study of the sintering and electrical properties of Mn-doped and Aldoped
ZnO ceramics, since these dopants play important roles in ZnO
varistors.
In this work, samples of undoped, Mn-doped, and Al-doped ZnO ceramics
were prepared via conventional ceramic processes, and the dopants were
incorporated using ethanol solutions of Mn(NO3)2.4H2O and Al(NO3)3.9H2O.
The solid solution and second phases in Al-doped and Mn-doped ZnO
ceramics were investigated by XRD, SEM with EDS, and TEM with EDS
techniques, in order to understand their effects on the sintering and electrical
properties of ZnO. The results showed that, for Al-doped ZnO, a second phase
of spinel ZnAl2O4 forms at ~800?C and is stable at higher temperatures. The
solid solubility of Al in ZnO was determined to be around 600 atomic ppm at
1200?C. For Mn-doped ZnO, a second phase of cubic ZnMnO3 is formed at
temperatures ? 450?C and transforms into another second phase of tetragonal
ZnMn2O4 at ~1100?C. The second phases gradually dissolve into the ZnO
phase and are no longer detected at 1200?C in the samples with Mn contents ?
1.2 mol%.
The densification and grain growth of ZnO doped with Al from 0.08 to 1.2
mol% were investigated during isothermal sintering between 1100? and
1400?C. The Al dopant significantly inhibits the grain growth of ZnO and
increases the grain growth exponent from 3, for undoped ZnO, to 4 – 6, for Aldoped
ZnO. The grain growth activation energy is also changed from ~200
kJ/mol, for undoped ZnO, to ~480 kJ/mol, for Al-doped ZnO. The
microstructural analysis showed that a ZnAl2O4 spinel phase exists as a second
phase and that the spinel particles exert an effective drag (pinning) on the
migration of ZnO grain boundaries. The analysis of the Al doping effect on the
densification rate provides evidence that the driving force for densification is
reduced by the second phase particles, too. A mechanism of pore-surface drag
(pinning) on densification equivalent to the observed grain-boundary drag
(pinning) on grain growth was proposed. [...]Os materiais cerâmicos baseados em ZnO têm sido objecto de estudo intenso devido às suas propriedades encontrarem larga aplicação tecnológica. O estudo da sinterização e das propriedades eléctricas do ZnO dopado é relevante pelas suas potenciais aplicações, nomeadamente em cerâmicos de resistência variável com a tensão (varistores). Neste contexto, o presente trabalho debruçou-se sobre os sistemas binários Mn-ZnO e Al-ZnO, já que ambos os dopantes são utilizados na formulação química daqueles materiais. Prepararam-se amostras de ZnO puro e dopado com manganês e alumínio pela via convencional de preparação de cerâmicos, usando para a incorporação dos dopantes soluções etanólicas de Mn(NO3)2.4H2O e Al(NO3)3.9H2O. Para clarificar os efeitos de solução sólida e de segundas fases na sinterização e nas propriedades eléctricas do ZnO, investigaram-se os aspectos microestruturais e cristalográficos das amostras dopadas com as técnicas de XRD e SEM e TEM com EDS acoplado. Os resultados mostraram que no ZnO dopado com Al forma-se uma segunda fase de espinela, ZnAl2O4, a ~800ºC, que é estável a temperaturas mais elevadas. Determinou-se um limite de solução sólida de cerca de 600 ppm em Al no ZnO a 1200ºC. No ZnO dopado com Mn forma-se uma segunda fase cúbica de ZnMnO3 a temperaturas iguais ou inferiores a 450ºC e que se transforma noutra segunda fase tetragonal de ZnMn2O4 a ~1100ºC. As segundas fases dissolvem-se gradualmente na fase de ZnO e a 1200ºC já não se detectam segundas fases nas amostras com teores de manganês iguais ou inferiores a 1,2 mol%. Investigou-se a densificação e o crescimento de grão do ZnO dopado com Al, de 0,08 a 1,2 mol%, durante a sinterização isotérmica entre 1100º e 1400ºC. A dopagem com Al inibe significativamente o crescimento de grão do ZnO e aumenta o expoente do crescimento de grão de 3, no ZnO puro, para 4- 6 no ZnO dopado com Al. A energia de activação do crescimento de grão também varia de ~200 kJ/mol, no ZnO puro, para ~480 kJ/mol no ZnO dopado com Al. A análise microestrutural mostrou que as partículas de espinela, ZnAl2O4, exercem uma travagem efectiva na migração das fronteiras de grão no ZnO dopado com Al. A análise do efeito da dopagem com Al na velocidade de densificação evidenciou também a redução da força motriz para a densificação pelas partículas da segunda fase de espinela. Foi proposto um mecanismo de travagem do movimento da superfície dos poros na densificação, equivalente ao efeito de arrastamento-travagem exercido pelas partículas de segunda fase nas fronteiras de grão, durante o crescimento de grão.
Mestrado em Engenharia de Materiais
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Arkun, Fevzi Erdem. "Study of Mn doped GaN for spintronic aApplications." 2006. http://www.lib.ncsu.edu/theses/available/etd-08172006-214234/unrestricted/etd.pdf.
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Hu, Hung-Ming, and 胡晃銘. "Magneto-impedance of Mn-doped ZnO magnetic semiconductors." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/54094366358953275541.
Full textAbstract:
碩士國立高雄師範大學
物理學系
93
This research is about making magnetic semiconductor material of Zn1-xMnxO by Solid-state sintering, and controlling the oxygen content in process. Diluted magnetic semiconductor（DMS）, is the material which mixes very few transitional mental atoms, and can show magnetic property in semiconductor material. To increase the proposal in usage, diluted magnetic semiconductor is combined with semiconductor property and magnetic, as well as of electron spin and electron charge. It is a new and original semiconductor material. In this research, we made different proportional Zn1-xMnxO, and did Magneto-impedance analysis of samples by X-ray diffraction(XRD), Vibrating Sample Magnetometer（VSM), and LCR meter. Besides, we also did analyze to its impedance spectra by using equivalent circuit analysis .The experimental result slows that if the proportion of Zn1-xMnxO is below X=0.08, its structural formation is based on ZnO(wurzite). And if the proportion is X=0.005, its hysteresis loops shows obvious ferromagnetic property; the more the proportion is, the less obvious the phenomenon is. As the change of the proportion, its dielectric constants show systematical change. The result of equivalent circuit analysis shows that the impedance of Zn1-xMnxO might have a largest existing in low frequency ( <50 Hz).
26
Huang, Po-Wei, and 黃柏瑋. "Ferromagnetism in Mn-doped III–V semiconducting materials." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/19684632156226111294.
Full textAbstract:
博士國立清華大學
材料科學工程學系
100
In this dissertation, we first investigate the in-plane magnetic anisotropy of Ga0.93Mn0.07As thin films grown on (001) and (311)A GaAs substrates. Temperature dependent magnetization (M?{T) measurements reveal a less enhancement in Curie temperature (TC) of the (311)A Ga0.93Mn0.07As upon annealing compared to the (001) counterpart. However, in the studies of magnetic hysteresis loops, the (311)A Ga0.93Mn0.07As exhibits a simple in-plane magnetic anisotropy with easy-axis consistently set along the crystallographic orientations, while deviated easy-axis was observed in both the as-grown and annealed (001) Ga0.93Mn0.07As. We analyzed the in-plane azimuthal magnetostatic energy and proposed an equation for calculating the angular dependent uniaxial and biaxial anisotropic energy and locating the easy-axis exactly. Next, we present a different observation on the exchange biasing of Ga0.95Mn0.05As by ultra thin (6 ?? MnOx. We have simultaneously observed exchange bias (HE) and vertical magnetization (M) shift in as-grown and field-annealed MnOx /Ga0.95Mn0.05As bilayers. HE initially decreases with increasing annealing time ta and then increases when ta > 30 min, while M shift remains almost unchanged with ta. X-ray photoelectron spectroscopy (XPS) analysis reveals that MnOx is composed of MnO and Mn3O4, and the volume amount ratio of Mn3O4 to MnO increases with increasing ta. A simple model of spin configurations based on a uniform MnO?{Mn3O4 interface with constant “pinned” uncompensated interfacial spins during field annealing is proposed to account for the observed exchange-biased phenomena. The last of this study is to explore the influences of the Mn concentration, growth temperature, and growth time on the structure and magnetic properties of (In, Mn)As nanostructures under Stranski?{Krastanov (S–K) growth mode. The (In, Mn)As nanodots and elongated dots (or nanowires), all have room-temperature ferromagnetism, can be grown at 320 oC ≦ Tg < 450 oC and Tg ≧ 450 oC, respectively. We particularly investigate the effects of the growth time and Mn concentration on the magnetic properties of the (In, Mn)As nanodots grown at 380 oC. Microstructure analysis reveals that the In1-xMnxAs nanodots with x < 0.44 present zinc-blende structure. For the In1-xMnxAs nanodots with x ≧ 0.44, a blocking temperature (TB) slight lower than TC can be located at the bifurcation between the zero-field-cooled and field cooled M?{T curves. For these nanodot samples with ultrahigh Mn concentration, the spin of dots exhibits a long-range order state at T < TB and the magnetic spin configuration is confirmed as superferromagnetic ordering by memory effect test. By analyzing the M?{T relations of the In0.56Mn0.44As nanodot samples with different growth times, a simple model is proposed to account for the spin configuration transition with quantum dots growth evolution. At last, it is found that high Mn concentration and high growth temperature are both necessary for the growth of well-ordered nanowires.
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tsai, Wei-xiang, and 蔡緯祥. "The study of Mn-doped ZnO thin film." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/95zf34.
Full textAbstract:
碩士國立臺北科技大學
光電工程系研究所
95
The ZnMnO thin films were grown on Si substrate by reactive magnetron sputter,and spraying pyrolysis method. X-ray diffraction measurement revealed both sample were wurtzite structure.No evident of any other secondary phases and impurities was detected. And Increasing Mn concentration caused the band-gap increased gradually. The Zn0.982Mn0.018O film were grown on Si substrate by spraying pyrolysis method ,exhibited a weak ferromagnetic characteristic with 77K.
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Su, Chih-Chuan, and 蘇志川. "Ultra-violet photoresponse of Mn doped ZnO nanowires." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/29752776375622763598.
Full textAbstract:
博士國立中興大學
物理學系所
102
In this thesis, an enhancement of ultra-violet (UV) sensing performance of Mn doped ZnO UV sensors was presented. Two different types of sensors were developed, including single nanowires sensor and nanoforest type sensor. Different fabricating processes of ZnO nanowires such as, vapor-liquid-solid method and low temperature aqueous solution method, were compared and discussed to optimize the photoresponse of Mn doped ZnO sensors. The mechanism, that Mn doping influence to the UV photoresponse of ZnO nanowires, was also suggested. Two methods were used to fabricate pure ZnO and Mn doped ZnO nanowires. In first method, ZnO nanowires were grown on Si(100) substrates with gold catalyze by vapor-liquid-solid method and then processed by ion-implantation to dope Mn. In another method, the reacting solution to growth pure ZnO nanowires by low temperature aqueous solution method containing Hexamethylenetetramine (HMTA, C6H12N4) and Zinc acetate (Zn(CH3COO)). For Mn doping, Manganese(II) chloride (MnCl2) was directly adding into the reacting solution. A series of analysis including FESEM (field emission scanning electron microscopy), EDS (energy dispersive spectroscopy), XRD (X-ray diffraction) and TEM (transmission electron microscopy) were performed to analyze the properties of ZnO nanowires. Results suggest a low temperature aqueous solution method is more suitable for fabricating ZnO nanowires UV sensors. Single ZnO or Mn/ZnO nanowire UV sensor was fabricated by focus ion beam deposition. The sensing abilities of ultra-violet sensors were examined under irradiation of 365 nm and 400 nm ultra-violet lights. The sensor with Mn doped ZnO nanowire showed an enhancement on sensing ability than the sensor with pure ZnO nanowire. Other ZnO and Mn/ZnO nanostructures UV sensors were also fabricated by low temperature aqueous solution method. The nanostructures were found to enhance the photoresponse of ZnO films. A possible mechanism, which related to surface sites of nanowires and desorption of gas molecules, was suggested to explain the results. The mechanism suggested that the Mn atoms near to surface of ZnO nanowires can influence UV photoresponse according to model of oxygen and water molecules desorption and re-adsorption. Nanoforest type UV sensors were fabricated in used of three different types of substrate and were grown by low temperature aqueous solution method. Mn doping level were controlled by adjust concentrations of chemicals in reacting solutions. Nanowires growing on different substrates were found have different morphologies. In compare of three kinds of substrates, substrates type II, which have ~180nm ZnO seed layer deposited by sputter, are found most suitable to fabricate nanoforest type UV sensor. The ZnO or Mn doped ZnO nanowires can grow on the substrates type II vertically. A model was suggested that nanowires forest were playing a role of charges’ buffer or reservoir. First principle calculations were performed to understand the properties of Mn doped ZnO nanowires. Results of first principle calculations showed that doped Mn atoms were prefer to stay at shell of ZnO nanowires. Band structures of ZnO and Mn doped ZnO nanowires were also simulated.
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Chung, Ming-Fang, and 鍾明芳. "Preparation and characterization of Mn doped ZnO nanoparticles." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/55635186926127668789.
Full textAbstract:
碩士國立高雄應用科技大學
化學工程與材料工程系
97
Mn-doped ZnO nanoparticels were prepared by a low temperature route at alkaline condition using zinc acetate, cetylpyridinium chloride and manganese acetate as the precursors. Scanning electron microscopy showed the diameters of ZnO nanoparticles were around 20-30 nm. X-ray diffraction demonstrated that the products were single crystal of ZnO; however, the d-spacing was slightly higher than the theoretical values, which could be attributed to the incorporation of Mn and formation of manganese oxides, as indicated TEM electron diffraction data. The Mn-related vibration was observed in Raman measurement; additionally, the E2 binding modes shifted to lower wave number as increasing the concentration of doped Mn. In addition, the vibration of Mn2O3 and ZnMn2O4 were found. Raman spectra showed that the as-prepared nanoparticles were Mn-doped ZnO and rare manganese oxides. Fluorescence luminance analysis indicated that the emission intensity of ZnO decreased and a blue shift UV emission were observed when ZnO was incorporated with Mn. Besides, a blue shift was also found the UV/visible adsorption spectrum of the Mn-doped ZnO nanoparticles. There indicates that the energy gap increased with the increase in the concentration of doped Mn. The ZnO doped with low concentration of Mn showed a higher photocatalytic activity than undoped ZnO. However, the photocatalytic activity of Mn-doped ZnO decreased when Mn-doped was higher than 0.3 mol%. Additionally, the photocatalytic activity of ZnO at visible light could no enhance by the incorporation of Mn.
30
Hung-YiChu and 朱閎逸. "Optical, magnetic and electrical properties of S-doped and dilute Mn-doped ZnO nanowires." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/af9pwy.
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Chia-HuiLee and 李佳輝. "Investigation of Mn-doped GaN Intermediate Band Solar Cells." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/80312398914416341882.
Full textAbstract:
碩士國立成功大學
光電科學與工程學系
100
In this study we focused on the optical and electrical characteristics of Mn-doped GaN for application in the intermediate band solar cells (IBSCs). In the beginning we investigated Mn-doped GaN by transmittance spectrums, hall measurement and PL. According to the transmittance spectrums, the Mn-doped GaN exhibited that the Mn-related intermediate band was formed in the forbidden band of GaN. Therefore, apart from absorbing the photons with energy more than the band gap energy of GaN, the photons with energy that was higher than the difference between the intermediate band and the conduction (valence) band could also be absorbed. So we used the Mn-doped GaN as the active layer of solar cells, expecting that the intermediate band of Mn-doped GaN could contribute more photocurrent. In our work, we fabricated two kinds of Mn-doped GaN intermediate band solar cells. The difference was the window layer. One was p-AlGaN and the other was p-GaN. Then we discussed the influence of the different window layers applied to intermediate band solar cell and expected the intermediate band could enhance the photocurrent. The more details would be discussed in this dissertation .
32
Stuckey, Aaron M. "X-ray studies of Mn doped III-V materials." 2005. http://etd.nd.edu/ETD-db/theses/available/etd-02232005-112555/.
Full text
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Kin, You-Chen, and 林宥辰. "Photoelectric and magnetic properties of Mn doped ZnO nanowires." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/32248285380270723328.
Full textAbstract:
碩士國立中興大學
奈米科學研究所
100
There are three parts in this thesis. First, Vapor-Liquid-Solid (VLS) method was used to grow Zinc Oxide nanowires. By adjusting the growing condition, the morphology of ZnO nanostructure can be controlled to grow as suitable shape for devices fabricating. Scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), energy dispersive spectrometer (EDS) and other analyzing instruments were then used to determine the material properties, such as morphology, crystal structures, grown orientation and, composition of zinc oxide nanowires. In second part, manganese ion was doped into zinc oxide nanowires by ion implantation. Variety of analyzing instruments same as first part were also used to determine the properties of morphology and crystal structures of manganese doped zinc oxide nanowires. In third part, E-beam lithography and Focus Ion Beam (FIB) were used to fabricate electrodes on nanowires. Electronic properties of zinc oxide nanowires and manganese doped zinc oxide nanowires were then determined. After all, the property, that resistance of zinc oxide nanowires can change with ultra-violet (UV) irradiation, was used to fabricate single nanowires based UV detectors.
34
Ming-WenHsiao and 蕭名雯. "Studies of Mn-doped InGaN Applied to Solar Cells." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/55353485867013653137.
Full textAbstract:
碩士國立成功大學
光電科學與工程學系
101
InGaN alloys has been predicted that a full-solar-spectrum material system could be achieved by the confirmation of InN with its energy band gap around 0.7 eV. With the combination of InXGa1-XN alloy systems, one may theoretically design tandem photovoltaic devices with optimum band gaps to absorb photon energy between 0.7 eV of infrared and 3.4 eV of ultraviolet regions. In this study, Mn-doped InGaN materials were grown by metalorganic vapor phase epitaxy, and their characterization and properties studied. By using X-ray, transmittance, photoluminescence and electrical properties, the Mn-doped InGaN-based materials and devices were studied. We conjecture that the poor quality of Mn-doped InGaN-based materials were attributed to Mn-relative impurity states in the materials. We fabricated the Mn-doped InGaN-based solar cells device in this research. The measurements of transmittance spectrum, relative external quantum efficiency and two photons external quantum efficiency showed the presence of an Mn-relative impurity states that appeared to be intermediate band absorption property, but the efficiency, Voc, Jsc, FF decreased due to the poor quality of Mn-doped InGaN material and high series resistance. Further details of the finding will be discussed in the dissection.
35
Hsieh, Ting-Yen, and 謝廷晏. "Spin dynamics and exchange interaction in Mn-doped GaN." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/60356368873518559935.
Full textAbstract:
碩士國立交通大學
電子物理系所
101
Mn-doped GaN has been known as a promising candidate for dilute magnetic semiconductor (DMS) working at room-temperature. However, the carrier-mediate ferromagnetism is still under debate unlikely in Mn-doped GaAs. In this work, electron spin dynamics in GaN and Mn-doped GaN were investigated by time-resolved Kerr rotation (TRKR) spectroscopy, which plays an important role in transferring spin information between different Mn atoms. With the increasing Mn concentration, the electron spin shows a shorter lifetime and a larger g factor. In particular, the g factor exhibits a linear dependence on the Mn concentration, which is caused by interacting with more Mn atoms in unit volume. The s-d exchange energy N0α = 0.35 eV is determined by fitting procedure.
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Shih, I.-Chuan, and 施奕全. "Magnetic and optical properties of Mn doped ZnO thin films." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/96871299438024738694.
Full textAbstract:
碩士國立高雄大學
應用物理學系碩士班
98
ZnO:Mn thin films is grown on glass substrates at room temperature by Radio frequency magnetron sputtering system. We expect to produce a piezoelectrical material possessing a well-coexsistent with magnetic and semiconductor's photoelectric quality by doping Manganese preparation. It expects to get the best condition of deposition under the vary parameters, such as the deposition mode, PF plasma power and working pressure. We discuss the annealing condition and the change in the ratio of argon to nitrogen, which are the doping growth gases. AFM, XRD, N&K analyzer, XPS and MCD were used to measure the thin surface morphology, thickness, structure, transmittance, ingredient analysis and magnetism. In ZnO: Mn thin films is grown by Radio frequency magnetron sputtering system experimental result, we found deposits under the RF Power highest and pressure smallest condition. From XRD picture may discover that Peak has the displacement deviation small angle migration, In the ZnO: Mn thin films growth by radio frequency magnetron sputtering system experiment at room temperature, we can find a small peak displacement to small angle side from XRD picture at the maximum deposition walt and minimum pressure condition, expressed that band gap changes is small. Through the MCD measurement in the magnetic field, we found that the magnetism is enhanced after annealing.
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Hsu, Den-Kai, and 許登凱. "Study of resistive switching behaviors for Mn doped ZnO nanorods." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/46149220634369114424.
Full textAbstract:
碩士國立清華大學
材料科學工程學系
99
There are two approches to enhance the resistive switching behavior in ZnO-based RRAM. One is trying to improve the resistive switching characteristics through the nanorods-limited geometry in ZnO-based RRAM devices. The other is trying to adjust concentration of dopant, Mn, which would increase the operative resistance window as the concentration increases. In addition, the higher resistance ratio, the faster programming speed properties of RRAM are suitable for development as a high-density memory. First of all, Mn-doped ZnO nanorods can be controlled growth successfully with different diameter and aspect ratio by hydrothermal method. We analyzed the surface morphology, crystalline structure and the composition of Mn-doped ZnO nanorods by SEM, XRD, TEM, EDX, and PL. We measured resistive switching behaviors of the Mn-doped ZnO nanorods by Keithley 4200. The resistive switching characteristics were observed and fell into three categories. First, different resistive switching behaviors can be observed in different types of devices, undoped and Mn-doped ZnO nanorods. Second, the resistive switching characteristics can be modified by different contents of Mn and different lengthes of ZnO nanrods. Furthermore, multistate memory effects could be manipulated by applying different current compliance in the device.
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Feng-WenHuang and 黃鋒文. "Characterization of Mn-doped GaN-based material and device application." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/29631859153315986072.
Full textAbstract:
博士國立成功大學
光電科學與工程學系
100
In present dissertation, characterization of Mn-doped GaN-based material and device application grown by metalorganic vapor phase epitaxy (MOVPE) were investigated. The surface morphology, crystallinity, optical, electrical, magnetic properties, electron binding energy and relative external quantum efficiency (photo-response) of Mn-doped GaN-based material and devices were studied. The memory effect and redistribution of manganese (Mn) into subsequently regrown GaN-based epitaxial layers by metalorganic vapor phase epitaxy were revealed. Low-temperature up-converted photoluminescence (UPL) and the secondary ion mass spectrometry were performed on GaN-based epitaxial samples with and without Mn doping to study the effect of residual Mn on optical property. UPL emission, which originated from residual Mn doping in regrown InGaN quantum wells (QWs) because of the memory effect of the reactor, could be eliminated in an air-exposed and H2-baking manner prior to the regrowth of the QWs. Considerable residual Mn background level and slow decay rate of Mn concentration tail were also observed in the regrown epitaxial layers, which could be attributed to the memory effect or surface segregation and diffusion from the Mn-doped underlying layer during regrowth in the Mn-free reactor. The surface segregation of Mn on the Mn-doped layer could be partially removed by hydrogen chloride-etched treatment. Competition between Mn and In atoms during the growth of InGaN material was also addressed in the current study. An up-conversion phenomenon was observed due to the Mn doping effect in the GaN-based material. Here, we further investigated the possible mechanism of the up-converted photoluminescence. Up-converted heterostructures with a Mn-doped underlying GaN intermediate band photodetection layer and an InGaN/GaN multiple quantum wells (MQWs) luminescence layer grown by metal-organic vapor-phase epitaxy were demonstrated. The up-converters exhibited a significant up-converted photoluminescence (UPL) signal. Power-dependent UPL and spectral responses indicated that the UPL emission could be due to photo-carrier injection from the Mn-doped GaN layer into InGaN/GaN MQWs. Photons convert from 2.54 to 2.99 eV via a single-photon absorption process to exhibit linear up-conversion photon energy of ~450 meV without applying bias voltage. Therefore, the up-conversion process could be interpreted within the uncomplicated energy-levels model. Intermediate band (IB) p-i-n solar cells with Mn-doped GaN absorption layer grown by metal-organic vapor-phase epitaxy were presented. The measurements of transmittance spectrum and relative external quantum efficiency (EQE) showed the presence of an IB absorption property. The IB devices showed additional infrared-visible-light region response and could be promising in high-efficiency solar cell applications. A large enhancement in short circuit current-density and a slight decrease in open circuit voltage were observed. The increased photocurrent of the cells without too much voltage reduction was a key point for IB operation. Power-dependent dual-light source excitation and lock-in amplifier techniques were performed to prove that “two-photon absorption process” actually takes place in IB solar cells with Mn-doped GaN absorption layer. Mn-doped InxGa1-xN material showed potential in high-efficiency solar cell applications by its effective usage in IB photovoltaic devices. Furthermore, the intermediate band solar cells with Mn-doped In0.084Ga0.916N absorption layer were presented initially. The efficiency was decreased due to the decrease of the Voc, Jsc and FF. The decreased efficiency could be attributed to the poor quality of Mn-doped InGaN material and the photon selectivity issue. The decreased Jsc was attributed to the decreased photocurrent due to the large non-radiative recombination associated with the poor quality, the photon selectivity issue and the high series resistance of Mn-doped InGaN even though the devices exhibited the additional absorption of the photons with energy below the VB-CB bandgap. Furthermore, the material quality of InGaN should be improved and the absorption of photon selectivity issue should be considered. The using of light confinement and the large thickness of Mn-doped InGaN would be necessary to efficiently absorb the lower energy photons with the weak absorption coefficient for the realization of IB photovoltaic devices. In addition to the issues of Jsc and Voc, obtaining a high FF for improving cell efficiency was also a key point. Therefore, attention should be focused on the reduction of series resistance to improve conversion efficiency by incorporation IB into the absorption layer of solar cells.
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Lin, Chih-an, and 林志安. "The study of Mn doped BiFeO3 by RF magnetic sputtering." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/03591514725897348116.
Full textAbstract:
碩士國立成功大學
材料科學及工程學系碩博士班
96
BiFeO3(BFO) is one of the most potential multiferroic materials for new device applications. This is because BFO has high ferroelectric Curie temperature (850oC) and antiferromagnetic Neil temperature (370oC), which are both above room temperature. This research mainly investigated the effects of manganese doping, i.e. BiFe1-XMnXO3 x = 0, 0.1, 0.2, 0.3, 0.4, on the BFO properties. Because BiMnO3 (BMO) is a ferroelectric ferromagnet and also, Mn3 + ion has a similar radius to Fe3 + ion, it was expected to be able to replace some Fe3 + with Mn3 +, resulting in new magnetic properties in the mixed compound BiFe1-XMnXO3 (BFMO). This experiment utilized RF magnetic sputtering to deposit films on the Si, SrTiO3 and LaAlO3 substrates at room temperature, which were subsequently sintered at high temperatures to form the desired phase. X-rays diffraction (XRD) was used to analyze the phase purity and structures of the prepared films, X-ray photoelectron spectroscopy (XPS) was used to study the ion bonding valence, field-emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM) was used to observe the surface morphology of the films, and finally superconducting quantum interference device (SQUID) was used to measure the magnetization-magnetic field (M-H) hysteresis loops in order to understand the magnetic properties of the films. We found that more impurity phases appeared with more addition of Mn, indicating that there was a limit for Mn doping in BFO. By the XPS analysis, it was shown that with the increased amount of Mn doping, the grain size of films became smaller . AFM showed that the more Mn addition, the rougher of the surface. It was also found by SQUID measurement that with the addition of Mn (x=0.1) , there was an increase of the saturated magnetization of the doped films.
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Po-ChengChen and 陳柏成. "Characterization of Mn-doped GaN-based Intermediate Band Solar Cell." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/jduj4k.
Full textAbstract:
博士國立成功大學
光電科學與工程學系
105
The dissertation was focused on the optical and electrical characteristics of GaN-based intermediate band solar cells with Mn-doped GaN, Al1−xGaxN and In1−xGaxN absorption layer. The surface morphology, crystallinity, optical, electrical electron, binding energy of Mn-doped GaN-based material and devices were studied. As for the Mn-doped GaN and Mn-doped Al1−xGaxN intermediate band solar cell(IBSCs), we designed two kinds of experiments , which were two photo external quantum efficiency EQE、dual laser system to verify the existence of the intermediate band and analyze its electron transfer mechanism. And using high-concentrated illumination and low temperature to investigate the characteristics of Mn-doped GaN and Mn-doped Al1−xGaxN intermediate band solar cells (IBSCs) with high power light input The IBSCs with a Mn-doped In1−xGaxN absorption layer were presented in our previous work. However, their efficiencies were not as expected. The material quality of In1−xGaxN should be improved, and the photon absorption selectivity issue should be considered. The EL spectra anomalous temperature behavior of the peak energy is S-shaped (decrease–increase–decrease). As a result of the large lattice mismatch between InN and GaN, their low miscibility led to In aggregation and phase separation. Furthermore, significant strains were formed in the In1−xGaxN host material. Previous studies showed that spinodal decomposition produced quantum-dot-like structures around the designated In1−xGaxN layers. The cluster structures formed spatial potential fluctuations and localized energy states for trapping carriers. In addition to the issues of Jsc and Voc, achieving a high FF to improve cell efficiency is also a key point.
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Szu-MinChen and 陳思敏. "Impedance Spectroscopy Analysis of Mn-Doped Barium Calcium Titanate Ceramics." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/ze4zpz.
Full textAbstract:
碩士國立成功大學
資源工程學系
106
In this study, calcium-doped barium titanate (BCT) powders were used as the raw materials to study different amounts of acceptor doping effects on the microstructure, crystal structure, and electrical properties of BCT. The A/B ratio of (Ba0.92Ca0.08)Ti1.005O3 was set for Ti-excess to prevent Ca doping onto the B-site. Powder of (Ba0.92Ca0.08)Ti1.005O3 was calcined at 1100°C which temperature can make the powder no second phase. Based on the Rietveld analysis results, Ca in the BCT mainly entered A-site to replace Ba. To simulating the MLCC sintering condition, the BCT ceramics should be sintered in reduction atmosphere to prevent the Ni electrode oxidation, and we also add different amounts of MnCO3 as acceptor to prevent the ceramic samples from semiconduction. The grain sizes after sintering are approximately 0.36 μm which fits the MLCC condition. In this study, We use two RQ equivalent circuit model to fit the impedance spectroscopy data, and the results meet the Curie-Weiss behavior. According to the impedance spectroscopy data, the grain and grain boundary conductivity of acceptor-doped BCT ceramics is determined by Vo ̈ and e' respectively. With the increase of the amount of addition, the grain and the grain boundary conductivity tends to increase. The similar grain and grain boundary conductivity of BCT ceramics are due to maintain the electric neutrality. While the depletion layer and grain boundary barrier height are tend to decrease as the amounts of acceptor increase. The comprehensive conclusions show that the amounts of acceptor (MnCO3) has a certain influence on the electrical analysis calculated by the impedance spectroscopy analysis.
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Cheng, Yu-Hung, and 鄭聿紘. "(Bi, Mn, Fe)-Doped Ceria Electrolyte Materials for IT-SOFCs." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/ph3sfd.
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碩士國立臺灣大學
材料科學與工程學研究所
106
The effects of bismuth, manganese and iron co-doping in ceria-based materials used as electrolyte of solid oxide fuel cells have been investigated in this study. The powders are synthesized by EDTA-citric acid method. The sintering behavior is analyzed by dilatometry (DIL) and density measurement. X-ray Diffraction (XRD) is used to identify crystalline phases. Microstructure of the samples is observed by various electron microscopies. Previous work (by J. Chiu) reported that the solubility limit of Mn and Fe in ceria is less than 1 at% while that of Bi is at 8-9 at% in the presence of Mn and Fe. Ce0.9(Bi0.09Mn0.5Fe0.5)O2 can be sintered dense only at 1050°C for 1 hr. Its coefficient of thermal expansion (CTE) is about 15.5x10-6 K-1 within 30-800°C, matches with CTE of LSCF-6428. Long-term stability of Bi-doped ceria can be improved by doping trace amount of Mn and Fe because the formation of second phase (r-Bi2O3) and vacancy ordering would be suppressed even annealing at 650oC for 100 hr. Finally, the anode-supported cells of 5 layers are assembled and improved. The improved cell containing 8YSZ (3.1 μm)/9HH (2.2 μm) bilayer electrolyte shows a maximum power output of 242 mW.cm-2 at 800°C.
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Fu, Chia-Hsien, and 傅家賢. "Characteristics of Mn-doped ZnO deposited by ultrasonic spray pyrosis." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/s59kz9.
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碩士國立臺北科技大學
光電工程系研究所
97
In this thesis, we manufacture the ZnO thin film by ultrasonic spray pyrosis method, and compare the relation between characteristics and growth temperature. Thus, according to this research, we obtain the optimal growth temperature which is 450℃. We allocate aqueous solutions (Zn(CH3COO)2+MnCl2+H2O) that includes growth compounds, use ultrasonic oscillation that results in vapor molecules adsorbing carrier gas through a furnace, and grow the ZnO thin film on a glass substrate. Next, the sample is examined by X-ray Diffractometer (XRD), Photoluminescence (PL), Raman Spectrum, Transmittance Spectrum, Scanning Electron Microscope (SEM), Energy Dispersive Spectrometer (EDS), Atomic Force Microscope (AFM). In addition, we also investigate the lattice constant, the energy gap, transmittance, the surface, element composition, and roughness of the sample. Under the same concentration, XRD is obtained when the growth temperature is enhanced. and EDS to find out the relationship between growth temperature and doping concentration. Besides, the thin film grows toward the direction of poly-crystal. Raman Spectrum we know that inelastic scattering of the growth Mn-doped ZnO is enhanced corresponding to different temperature. However, the E2 mode is decreased. It is known that it is much easier to form clusters on the surface in lower temperature and longer growth time due to the AFM analysis of thin film roughness. Transmittance through the sample corresponding to different wavelength absorption, and thus energy gap is achieved. We obtain the relation of doping concentration, energy gap, and luminescence intensity. Finally, the sample is exerted by magnetic flux for the variation of optical characteristics measurements in PL and Transmittance.
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Sung, Ping-Chan, and 宋秉純. "The Study of Mn Doped P-type ZnO Thin Films." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/9k6exd.
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碩士國立臺北科技大學
光電工程系研究所
97
The diluted magnetic semiconductor(DMS) material which combined the magnetic material and material characteristic of the semiconductor has been the subject studied all the time. In this study,at first we deposit the ZnSbO(SZO) films by Ultrasonic Spray Pyrolysis(USP) method.We confirm the structure by X-ray diffraction analysis,and examine the SZO thin films for p-type.Then we deposit the ZnMnSbO (ZMSO) thin films by co-doped antimony and manganese. We establish the structure by X-ray diffraction analysis. Finally,we examine magnetic by SQUID. Superconductive quantum interferercn(SQUID) at the room temperature (300K) measures the curve of magnetism,. So we inference this thin film has ferromagnetism under 300K.The Curie temperature (Tc) Exceed the room temperature.
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Liu, Chia-Yun, and 劉珈芸. "Room temperature ferromagnetism exhibited in Mn-doped ZnxSn1-xO3 films." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/afgsea.
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碩士國立交通大學
電子物理系所
96
In this thesis, the fabrication of Mn-doped ZnxSn1-xO3 thin film on Al2O3 (0001) substrate by pulse laser deposition would be studied and were carried out to understand the origin of the ferromagnetism and the role played by changing the carrier concentration. Although in the present study the obtained a films appeared to contain two different phases, the existence of ferromagnetic property at 300K is reproducibly obtained for films deposited only at 700℃ with 10-3 torr of oxygen partial pressure. X-ray four-circle diffraction scan and ψ scan suggested that the existence of Mn containing ZnSnO3 phase might have resulted in the observed room-temperature ferromagnetism. With annealing treatment carried out at 300℃,the overall carrier concentration of the film can be changed. The results also showed that the effect magnetic moment in the ferromagnetic state indeed increased with increasing carrier concentration. Finally, we note that the average transmittance in the visible region is above 80％. The absorption spectrum shows that the optical bandgap is enhanced notably by Mn-doping. The increment of optical band gap value suggests a uniform substitution of Mn ions for Zn ions.
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尤隆禹. "The study of Co-doped P type and Mn-doped N type GaN Diluted Magnetic Semiconductors." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/49956709390425926275.
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Chen, Hui-Wei, and 陳慧薇. "Synthesis of ZnS and Mn-doped ZnS nanoparticles and its photoluminescence." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/87899132794837961550.
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Liu, Chu-Fang, and 劉筑芳. "Preparation and Characterization of Mn-doped BaTiO3 Films By RF Sputtering." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/66584669291830520740.
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碩士國立海洋大學
材料工程研究所
90
amorphous, as confirmed by XRD results, and started to crystallize at temperature of 600°C or above, depending the Mn content. The as-deposited films became generally refined as Mn content increased. Granular structures and clusters were seen in SEM micrographs of post-annealed films, and the clusters were larger and densed with increasing Mn contents. DSC results revealed that the activation energies for crystallization and cubic-to-hexagonal structure phase transformation are ~100 and ~500 kJ/mole, varying with the Mn content Effects of Mn have also been observed on film leakage current and dielectric constant.
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Zong-ShengZeng and 鄭宗昇. "Photovoltaic Characteristics Studying of Mn-doped GaN Intermediate Band Solar Cells." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/rzdkp6.
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碩士國立成功大學
光電科學與工程學系
102
In this study we focused on the optical and electrical characteristics of Mn-doped GaN for application in the intermediate band solar cells (IBSCs). In the beginning we investigated Mn-doped GaN by transmittance spectrums and low temperature PL. According to the transmittance spectrums, the Mn-doped GaN exhibited that the Mn-related intermediate band was formed in the forbidden band of GaN. Therefore, apart from absorbing the photons with energy more than the band gap energy of GaN, the photons with energy that was higher than the difference between the intermediate band and the conduction (valence) band could also be absorbed. So we used the Mn-doped GaN as the active layer of solar cells, expecting that the intermediate band of Mn-doped GaN could contribute more photocurrent. As for the intermediate band solar cell(IBSCs),we designed two kinds of experiments , which were two photo external quantum efficiency EQE、dual laser system to verify the existence of the intermediate band and analyze its electron transfer mechanism. And using high-concentrator solar simulator to investigate the characteristics of Mn-doped GaN intermediate band solar cells (IBSCs) with high power light input. That the difference flow rate of Mn in GaN active layer affect intermediate band solar cells (IBSCs) are also compared , we expect the absorbtion of photons with energy that was higher than the difference between the intermediate band and the conduction (valence) band could devote extra photocurrent , and improve efficiency . The more details would be discussed in this thesis.
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Hsieh, Hsu-Min, and 謝旭閔. "Preparation and Characterization of Mn-doped CeO2 by Sol-Gel Method." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/y686st.
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碩士國立屏東科技大學
機械工程系所
106
Global environmental protection is a well-known and important issue. The concept of greening the earth is used to protect the earth all over the world. However, the quality and demand for people's livelihood supplies have increased, which has led to the rise of various manufacturing industries, and the manufacturing industry has flourished. They cause water pollution and air pollution. In order to improve people's quality of life, many research scholars have focused on the research and development of photocatalyst and photocatalysis, in order to improve the catalytic efficiency of photocatalyst and degrade the dye wastewater which discharged from the dyeing and finishing industry. In this study, triblock copolymer was utilized as surfactant, Ce(NO3)3‧6H2O as precursor of the host, and MnCl2‧4H2O as precursor of doping. And then, Mn-doped cerium oxide was synthesized by sol-gel method as specimen. The calcination was carried out at 550, 600 and 650 ℃, respectively. The prepared powder was then used for photocatalytic degradation of methylene blue to improve environmental pollution. The characteristic of the specimen was analyzed by TGA, FTIR, XRD, SEM and TEM. Uv-visible light was used for photocatalysis degradation, determining the absorption rate and degradation efficiency of cerium oxide doped manganese. According to the experimental results, the minimum grain size of the CM10 at 600 ℃ is 17.52 nm, and the degradation efficiency is 28.39%. The best degradation efficiency is Pure CeO2 at 650 ℃, the degradation efficiency is 46.44%; therefore, doping Mn can effectively inhibit grain growth, but can’t improve the degradation efficiency in the visible light band, but can have degradation efficiency close to Pure CeO2, such as CM01 at 600 ℃, its degradation efficiency reaches 44.55 %