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Liu, Jia. "Optical spectroscopic study of GaAs with dilute nitrogen doping /." View Abstract or Full-Text, 2002. http://library.ust.hk/cgi/db/thesis.pl?PHYS%202002%20LIU.
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Wellenius, Patrick. "Nitrogen Doping and Ion Beam Processing of Zinc Oxide Thin Films." NCSU, 2006. http://www.lib.ncsu.edu/theses/available/etd-01042006-015801/.
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The modification of single crystal epitaxial ZnO thin films grown by Pulsed Laser Deposition on c-axis oriented sapphire substrates by Ion Beam Processing was investigated. Nitrogen doping of the films was attempted using nuclear transmutation using the 16O (3He, 4He) 15O reaction at 6.6 MeV. The 15O product is unstable and decays to 15N after several minutes by positron emission. There are several potential advantages to using nuclear transmutation including producing nitrogen atoms on the correct lattice site for doping and reduced crystal damage as compared to conventional ion beam implantation. In the experiments in this thesis the doping levels achieved ~1014 cm-3 were too low to be expected to dope the films to p-type. However several beneficial effects due to the ion beam processing were observed, including large increases in resistivity, reduction of defect luminescence, and substantial increases in the response of photoconductive detectors. In addition to desired effects in some films it was also found that in some films bubble like structures approximately 10 ìm in diameter were formed where the thin film delaminated from the surface. It was assumed that mechanism for the bubble formation was the build up of helium gas at the sapphire/ZnO interface.
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Moldovan, Monica. "Photoluminescence investigation of compensation in nitrogen doped ZnSe." Morgantown, W. Va. : [West Virginia University Libraries], 1999. http://etd.wvu.edu/templates/showETD.cfm?recnum=740.
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Thesis (Ph. D.)--West Virginia University, 1999.Title from document title page. Document formatted into pages; contains xiv, 154 p. : ill. Includes abstract. Includes bibliographical references (p. 148-154).
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Mawudoku, Daniel, George Affadu_Danful, Caitlin Millsaps, and Gregory Bishop. "Immobilization of Electrocatalytically Active Gold Nanoparticles on Nitrogen-Doped Carbon Fiber Electrodes." Digital Commons @ East Tennessee State University, 2019. https://dc.etsu.edu/asrf/2019/schedule/106.
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Immobilization of Electrocatalytically Active Gold Nanoparticles on Nitrogen-Doped Carbon Fiber Electrodes
ABSTRACT
Recently, immobilization of single metal nanoparticles on nanometer-sized electrodes has been demonstrated as a means to electrochemically probe the relationship between nanoparticle structure and function. Such studies of individual, isolated nanoparticles enable investigation of electrochemical behavior and electrocatalytic properties in the absence of complicating factors like interparticle distance and nanoparticle loading that are typically associated with collections of particles distributed on electrode supports. However, interpretation of electrochemical data obtained from single nanoparticle immobilization experiments can also be difficult since the underlying nanoelectrode platform can sometimes contribute to the measured current or the immobilization strategy may have adverse effects on electron transfer. Here we report immobilization of gold nanoparticles on relatively catalytically inert carbon fiber ultramicro- and nanoelectrodes through a modification method based on recently reported soft nitriding process found to be effective in attaching ligand-free ultrasmall noble metal catalysts to activated carbons. X-ray photoelectron spectroscopy results reveal that the nitriding of carbon fibers provides 3.5 times increase in surface nitrogen content, introducing mostly pyridinic and amine nitrogen groups. The nitrogen-containing surface sites proved to be beneficial to the deposition of gold nanoparticles (AuNPs), as sodium borohydride reduction of tetrachloroaurate resulted in attachment of AuNPs on nitrided carbon fiber ultramicroelectrodes (N-CF-UMEs) in as little as 10 seconds while immobilization of AuNPs on unmodified CF-UMEs required at least 12 hours. A recently reported electrochemical method was employed to characterize immobilized AuNPs, and AuNP size was found to be directly related to deposition time. AuNPs immobilized on N-CF-UMEs also exhibited electrocatalytic activity towards methanol oxidation. Reduction of electrode size will enable this strategy to be employed to investigate electrochemical behavior of individual gold nanoparticles, while the ligand-free nature of the immobilized particles also provides the opportunity to investigate effects of surface capping agents on electrocatalytic properties.
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Chindanon, Kritsa. "Nitrogen doping in low temperature halo-carbon homoepitaxial growth of 4H-silicon carbide." Master's thesis, Mississippi State : Mississippi State University, 2008. http://library.msstate.edu/etd/show.asp?etd=etd-07102008-045510.
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Villalpando, Paéz Federico. "Effects of doping single and double walled carbon nanotubes with nitrogen and boron." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/36215.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2006.Includes bibliographical references (p. 135-143).
Controlling the diameter and chirality of carbon nanotubes to fine tune their electronic band gap will no longer be enough to satisfy the growing list of characteristics that future carbon nanotube applications are starting to require. Controlling their band gap, wall reactivity and mechanical properties is imperative to make them functional. The solution to these challenges is likely to lie in smart defect engineering. Defects of every kind can induce significant changes on the intrinsic properties of carbon nanotubes. In this context, this thesis analyzes the effects of doping single and double walled carbon nanotubes with nitrogen and boron. We describe the synthesis of N-doped single-walled carbon nanotubes (N-SWNTs), that agglomerate in bundles and form long strands (<10cm), via the thermal decomposition of ferrocene/ethanol/benzylamine (FEB) solutions in an Ar atmosphere at 950°C. Using Raman spectroscopy, we noted that as the N content is increased in the starting FEB solution, the growth of large diameter tubes is inhibited. We observed that the relative electrical conductivity of the strands increases with increasing nitrogen concentration. Thermogravimetric analysis (TGA) showed novel features for highly doped tubes, that are related to chemical reactions on N sites.
(cont.) We also carried out resonance Raman studies of the coalescence process of double walled carbon nanotubes in conjunction with high resolution transmission electron microscope (HRTEM) experiments on the same samples, heat treated to a variety of temperatures and either undoped or Boron doped. As the heat treatment temperatures are increased (to 1300°C) a Raman mode related to carbon-carbon chains (w = 1855cm-1) is observed before DWNT coalescence occurs. These chains are expected to be 3-5 atoms long and they are established covalently between adjacent DWNTs. The sp carbon chains trigger nanotube coalescence via a zipper mechanism and the chains disappear once the tubes merge. Other features of the Raman spectra were analyzed as a function of heat treatment with special emphasis on the metallic or semiconducting nature of the layers constituting the DWNTs. DWNTs whose outer wall is metallic tend to interact more with the dopant and their outer tubes are the predominant contributors to the line shape of the G and G' bands.
(cont.) The metallic or semiconducting nature of the layers of the DWNTs does not affect their coalescence temperature. All the experiments and analysis presented in this thesis are the result of a collaborative effort between Professor Dresselhaus' group at MIT and its international collaborators, including Professor Endo's group at Shinshu University, Nagano, Japan, Professors Pimenta's and Jorio's group at the Federal University of Minas Gerais, Belo Horizonte, Brazil, and Professors M. and H. Terrones' group at IPICYT, San Luis Potosi, Mexico.
by Federico Villalpando Paéz.
S.M.
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Kuo, Ming-Tsun. "Field emission and annealing studies of n-type doped hydrogenated amorphous carbon films." Thesis, University of Bristol, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.340300.
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Sanwick, Alexis. "Heteroatom-Doped Chemical Vapor Deposition Carbon Ultramicroelectrodes." Digital Commons @ East Tennessee State University, 2020. https://dc.etsu.edu/honors/592.
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Metal nanoparticles have been a primary focus in areas of catalysis and electrocatalysis applications as a result of their large surface area-to-volume ratios. While there is an increased interest in understanding the properties and behaviors of metal nanoparticles, they can become expensive over time. Recent research has incorporated the idea of using heteroatom-doped materials as a cheaper catalytic alternative to metal nanoparticles. In this study nitrogen-doping and phosphorous-doping techniques were applied to chemical vapor-deposited carbon ultramicroelectrodes in order to study the electrocatalytic properties toward the oxygen reduction reaction and the enhanced affinity for the deposition of gold nanoparticles onto the electrodes.
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Wornyo, Eric. "Nitrogen-Doped Carbon Fiber Ultramicroelectrodes as Electrochemical Sensors for Detection of Hydrogen Peroxide." Digital Commons @ East Tennessee State University, 2021. https://dc.etsu.edu/etd/3960.
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Carbon fiber ultramicroelectrodes (CF-UMEs) are commonly used as electrochemical probes and sensors due to their small size, fast response, and high signal-to-noise ratio. Surface modification strategies are often employed on CF-UMEs to improve their selectivity and sensitivity for desired applications. However, many modification methods are cumbersome and require expensive equipment. In this study, a simple approach known as soft nitriding is used to prepare nitrogen-doped CF-UMEs (N-CF-UMEs). Nitrogen groups introduced via soft nitriding act as electrocatalytic sites for the breakage of O-O bonds during the reduction of peroxides like H2O2, a common target of biosensing strategies. Voltammetric studies confirm that, compared to CF-UMEs, N-CF-UMEs possess enhanced electrocatalytic activity towards H2O2 reduction as evidenced by an increase in current and positive shift in onset potential for the reaction. N-CF-UMEs also proved capable for amperometric detection of H2O2, exhibiting good linear response from 0.1 to 5.6 mM at -0.4 V vs. Ag/AgCl.
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Correa, Washington Luiz Alves. "Contribuição para a sintese de diamante com dopagens de boro, nitrogenio ou enxofre." [s.n.], 2004. http://repositorio.unicamp.br/jspui/handle/REPOSIP/260578.
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Orientador: Vitor BaranauskasTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação
Made available in DSpace on 2018-08-05T18:10:58Z (GMT). No. of bitstreams: 1 Correa_WashingtonLuizAlves_D.pdf: 3351242 bytes, checksum: 8f30a26c68d4c1e73a72d065eaedb4f9 (MD5) Previous issue date: 2004
Resumo: Estudamos processos de dopagem do diamante crescido por deposição química a partir da fase vapor (diamante CVD) com a introdução de impurezas dopantes durante o crescimento do diamante em reatores do tipo filamento-quente. Focalizamos nossa pesquisa na dopagem do diamante com boro, ou nitrogênio, ou enxofre, visando obter diamantes com propriedades semicondutoras com condutividade eletrônica (tipo n) ou condutividade por lacunas (tipo p). Foram utilizadas contaminações intencionais utilizando: trimetil borano (B(CH3)3), ou amônia (NH3), ou dissulfeto de carbono (CS2), misturados com metano e diluídos em hidrogênio. As amostras foram caracterizadas por microscopia eletrônica de varredura (SEM), espectroscopia Raman, espectroscopia de foto-elétrons excitados por raios X (XPS), espectroscopia de emissão de raios X excitado por feixe de prótons (PIXE) e efeito Hall. As dopagens do diamante do tipo p e do tipo n foram obtidas com contaminações de boro e enxofre, respectivamente. O diamante dopado com nitrogênio não apresentou propriedades semicondutoras
Abstract: We studied the diamond doping processes with introduction of doping impurities during the diamond growth in the chemical vapor deposition (CVD) technique, using a hot-filament reactor. Our research focused the use of boron, nitrogen or sulphur atoms in order to obtain diamond films with semiconductor properties of electronic (n-type) or hole (p-type) current transport mechanisms. Trimethyl-borane (B(CH3)3), or ammonia, or carbon disulphide (CS2), mixed with methane and hydrogen were used in the feed gas mixture. The diamond samples were characterized by scanning electron microscopy (SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), Proton-induced X-ray emission (PIXE) and Hall effect. p-type and n-type diamonds have been obtained with boron and sulphur doping, respectively. However, the nitrogen doped samples do not presented semiconductor properties
Doutorado
Engenharia de Eletronica e Comunicações
Doutor em Engenharia Elétrica
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Ogbu, Chidiebere. "Peroxide Sensing Using Nitrogen-Doped and Platinum Nanoparticle-modified Screen-Printed Carbon Electrodes." Digital Commons @ East Tennessee State University, 2019. https://dc.etsu.edu/etd/3622.
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Nitrogen-doped carbon materials have garnered much interest due to their abilities to behave as electrocatalysts for reactions important in energy production (oxygen reduction) and biosensing (hydrogen peroxide reduction). Here, we demonstrate fabrication methods and determine electrocatalytic properties of nitrogen-doped screen-printed carbon (N-SPCE) electrodes. Nitrogen doping of graphite was achieved through a simple soft-nitriding technique which was then used in lab-formulated screen-printing inks to prepare N-SPCEs. N-SPCEs displayed good electrocatalytic activity, reproducibility and long term stability towards the electrochemical reduction of hydrogen peroxide. N-SPCEs exhibited a wide linear range (20 µM to 5.3 mM), reasonable limit of detection of 2.5 µM, with an applied potential of -0.4 V (vs. Ag/AgCl). We also demonstrate that nitrided-graphite can similarly be used as a platform for the deposition of electrocatalytic platinum nanoparticles, resulting in Pt-N-SPCEs with a lower limit of detection (0.4 µM) and better sensitivity (0.52 µA cm-2 µM-1) towards H2O2 reduction.
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HINOJOSA, PAOLA ALEXANDRA AYALA. "IMPLICATIONS OF THE C/N FEEDSTOCK ON CONTROLLING THE NITROGEN DOPING AND BONDING ENVIRONMENT IN CARBON NANOTUBES." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2007. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=10399@1.
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CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOOs tópicos mais importantes a ser tratados nesta tese de doutorado são os vários problemas envolvidos na síntese de nanotubos contendo nitrogênio. Isto é principalmente motivado pelas possíveis aplicações que podem ser dadas a este tipo de estruturas. A motivação central está relacionada ao fato da possibilidade de fazer dopagens tipo -p e -n em nanotubos de carbono, incorporando átomos como boro ou nitrogênio. Isto está muito longe de ser uma trivialidade devido a que devemos levar em conta que se os nanotubos de carbono forem pensados como bases estruturais para nanocompósitos e dispositivos nanoeletronicos, é necessário controlar cuidadosamente a reatividade das paredes, sua dureza mecânica e o gap eletrônico por meio de um controle da quantidade de átomos inseridos nas paredes ou entre elas. Portanto, do ponto de vista de diferentes aplicações, é importante ter a possibilidade de dopar controladamente os nanotubos. Neste trabalho apresentam-se o quadro descritivo da dependência dos parâmetros de síntese, assim como uma investigação detalhada da formação de outras estruturas co-produto do processo de formação de nanotubos. Como uma idéia pioneira proposta neste trabalho, é enfatizado o uso de fontes puras de C/N em processos de síntese baseados em deposição química na fase de vapor. Desta maneira foi possivel determinar os efeitos da atmosfera de reação e o pretratamento do catalizador como agentes favoráveis ou desfavoráveis para a síntese efetiva de nanotubos de carbono.
The main topic of this thesis is the study of various issues related to the synthesis of nitrogen containing nanotubes. This is mainly inspired in the possible applications such structures can have. The practical background lies in the fact that defined n- and p-doping of carbon nanotubes can be achieved by substituting carbon atoms from the tube walls by heteroatoms such as boron or nitrogen (N). This is far from been a triviality because we must keep in mind that if carbon nanotubes are to be used as future building blocks in nanocomposites and nanoelectronic devices, it is imperative to fine tune their wall reactivity, mechanical strength and electronic band gap by controlling the amount of foreign atoms inserted into the tube lattices. Therefore, from an applications standpoint, it is important to be able to carefully control the insertion of different dopants into nanotubes. In this work, a complete picture of the dependence on the combined synthesis parameters is established and a fundamental insight into the formation of N doped nanotubes and other structures (co- products) is provided. As a pioneering idea of this whole work, the use of pure C/N feedstocks in chemical vapor deposition methods is emphasized. With this, it was possible to determine the effects of the reaction atmosphere and the catalyst pretreatment as either favoring or disfavoring agents towards the synthesis of N-doped nanotubes.
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Murphy, John Douglas. "The properties of nitrogen and oxygen in silicon." Thesis, University of Oxford, 2006. http://ora.ox.ac.uk/objects/uuid:d6ff6bba-f9ec-497b-b0f4-2d4162f784cc.
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A novel dislocation locking technique is used to study the behaviour of nitrogen and oxygen in silicon. Specimens containing well-defined arrays of dislocation half-loops are subjected to isothermal anneals of controlled duration, during which nitrogen or oxygen diffuses to the dislocations. The stress required to move the dislocations away from the impurities is then measured. Measurement of this unlocking stress as a function of annealing time and temperature allows information on the transport of nitrogen and oxygen to be deduced. Despite being present in a concentration of just 3E14cm-3 in some specimens, nitrogen is found to provide substantial benefits to the mechanical properties of float-zone silicon (FZ-Si). The segregation of nitrogen at dislocations is stable to at least 1200 degrees centigrade and the unlocking stress measured at 550 degrees centigrade is of similar magnitude to that found previously for oxygen in Czochralski silicon (Cz-Si). The unlocking stress initially rises linearly with annealing time, before it takes a constant value. The rate of the initial rise is dependent on temperature and the 1.5eV activation energy found agrees with that found previously. The rate of the initial rise also depends on nitrogen concentration. In the 500 to 700 degrees centigrade temperature range, the unlocking stress is found to decrease linearly as the temperature at which the unlocking process takes place increases. The results of a pre-annealing experiment confirm that oxygen monomers and dimers in Cz-Si exist in thermodynamic equilibrium at 550 degrees centigrade. Numerical simulation of oxygen diffusion to dislocations allows values of the effective diffusivity of oxygen in Cz-Si with four different oxygen concentrations to be deduced. At 500 degrees centigrade, the effective diffusivity depends upon oxygen concentration in a way which is consistent with oxygen dimers being responsible for transport. The transport of oxygen in Cz-Si at 550 to 600 degrees centigrade is found to be unaffected by nitrogen doping at a level of 2.1E15cm-3. The dislocation locking technique has also been used to study the effect of high concentrations of shallow dopants on oxygen transport in Cz-Si in the 350 to 550 degrees centigrade temperature range. Oxygen transport has been found to be unaffected by a high antimony concentration ~3E18cm-3, but is found to be enhanced by, on average, a factor of approximately 44 in Cz-Si with a high boron concentration ~5E18cm-3. Furthermore, deep-level transient spectroscopy (DLTS) and high-resolution DLTS (HR-DLTS) are used to study the electrical activity of defects in silicon. A deep-level with an enthalpy of 0.50eV and a concentration of order 10E11cm-3 is found in n-type nitrogen-doped FZ-Si and n-type nitrogen-doped neutron transmutation doped FZ-Si. No additional deep-levels are found in either material, for which the detection limit is 6E10cm-3. No deep-levels are found in p-type nitrogen-doped Cz-Si, for which the detection limit is approximately 10E12cm-3. DLTS and HR-DLTS are also used to investigate the electrical activity of oxygen-decorated dislocations in Cz-Si and states associated with oxygen at dislocation cores have been identified.
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Dahlberg, Tobias. "The first order Raman spectrum of isotope labelled nitrogen-doped reduced graphene oxide." Thesis, Umeå universitet, Institutionen för fysik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-116699.
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The topic of this thesis is the study of nitrogen functionalities in nitrogen-doped reduced graphene oxide using Raman spectroscopy. Specifically, the project set out to investigate if the Raman active nitrogen-related vibrational modes of graphene can be identified via isotope labelling. Previous studies have used Raman spectroscopy to characterise nitrogen doped graphene, but none has employed the method of isotope labelling to do so. The study was conducted by producing undoped, nitrogen-doped and nitrogen-15-doped reduced graphene oxide and comparing the differences in the first-order Raman spectrum of the samples. Results of this study are inconclusive. However, some indications linking the I band to nitrogen functionalities are found. Also, a hypothetical Raman band denoted I* possibly related to \spt{3} hybridised carbon is introduced in the same spectral area as I. This indication of a separation of the I band into two bands, each dependent on one of these factors could bring clarity to this poorly understood spectral area. As the results of this study are highly speculative, further research is needed to confirm them and the work presented here serves as a preliminary investigation.
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Krüner, Benjamin [Verfasser], and Volker [Akademischer Betreuer] Presser. "Polymer-derived carbides and carbons with and without nitrogen-doping for electrochemical energy applications / Benjamin Krüner ; Betreuer: Volker Presser." Saarbrücken : Saarländische Universitäts- und Landesbibliothek, 2018. http://d-nb.info/1173703136/34.
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Krüner, Benjamin Verfasser], and Volker [Akademischer Betreuer] [Presser. "Polymer-derived carbides and carbons with and without nitrogen-doping for electrochemical energy applications / Benjamin Krüner ; Betreuer: Volker Presser." Saarbrücken : Saarländische Universitäts- und Landesbibliothek, 2018. http://nbn-resolving.de/urn:nbn:de:bsz:291-scidok-ds-275535.
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Vasilenko, R. L., V. N. Voyevodin, V. I. Gritsyna, S. F. Dudnik, K. I. Koshevoi, O. A. Opalev, E. N. Reshetnyak, and V. E. Strel'nitskij. "The Effect of Gas Phase Composition on the Structural Characteristics and Resistivity of Nitrogen-doped Nanostructured Diamond Coatings." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35189.
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The experimental results of the effect of the gas phase composition on nitrogen-doped nanostructured
diamond coatings synthesized in the glow discharge plasma on their structure and resistance have been
presented. It was shown that changes in the electrical conductivity of the nitrogen doped nanostructured
diamond coatings are primarily related to changes in the electrical conductivity of the grain boundaries
and did not to changes in the grain size of the diamond phase.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35189
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Lin, Hong-Ying. "Improving the optoelectronic property and photoactivity of nano-structured titanuim dioxide effect of particle size, oxygen vacancy, and nitrogen doping /." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 1581 p, 2008. http://proquest.umi.com/pqdweb?did=1609302401&sid=2&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Thesis (Ph.D.)--University of Delaware, 2008.Principal faculty advisors: Chin-Pao Huang, Dept. of Civil and Environmental Engineering, and S. Ismat Shah, Dept. of Materials Science Includes bibliographical references.
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Ozaki, Hirotaka. "Effect of Si and Other Elements Modification on the Photocatalytic Activities of Titanias Prepared by the Glycothermal Method." 京都大学 (Kyoto University), 2008. http://hdl.handle.net/2433/57274.
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Kyoto University (京都大学)0048
新制・課程博士
博士(工学)
甲第13834号
工博第2938号
新制||工||1434(附属図書館)
26050
UT51-2008-C750
京都大学大学院工学研究科物質エネルギー化学専攻
(主査)教授 井上 正志, 教授 江口 浩一, 教授 田中 庸裕
学位規則第4条第1項該当
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Kanakaraj, Sathya Narayan. "Processing Carbon Nanotube Fibers for Wearable Electrochemical Devices." University of Cincinnati / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1573224577754985.
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Krishnan, Bharat. "DEVELOPMENT OF SIMULATION FRAMEWORK FOR THE ANALYSIS OF NON-IDEAL EFFECTS IN DOPING PROFILE MEASUREMENT USING CAPACITANCE ? VOLTAGE TECHNIQUE." MSSTATE, 2005. http://sun.library.msstate.edu/ETD-db/theses/available/etd-04082005-092339/.
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Silicon Carbide devices are proving to be most promising for high power and high-temperature application in recent times. Efficient and accurate characterization of the device characteristics is key to the fabrication of high quality devices and reproduction of the quality of the devices fabricated. Capacitance-Voltage profiling is one of the most commonly used techniques to measure the doping profiles of semiconductors. However, interpretation of C-V profiling in the presence of traps in the material becomes complicated. Various complications arising from compensation between donors and acceptors, partial ionization of dopants and presence of deep level impurities could yield anomalous measured profile. Silicon Carbide being a wide bandgap semiconductor, many impurities commonly found such as Boron and Aluminum are not completely ionized at Room temperature. This leads to complications in calculating doping profiles when the trap levels are deeper. Other complications arising due to series resistance effect and diode edge effect may also affect the measured profile. Accounting for these complications may be difficult by mere observation of the measured profile. Simulation can be an excellent tool to extract parameters of interest from experimental results that are influenced by non-ideal effects. Fitting of the experimentally obtained data with simulated profile using specific models may be a useful technique to quantitatively account for the deviations from the actual profiles.
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Amponsah, Sylvester. "Optical Characterization of Nitrogen-vacancy Centers andResonance Analysis of CVD Grown Diamond MEMS Devices." Case Western Reserve University School of Graduate Studies / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=case1528479091207253.
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Ramamurti, Rahul. "Synthesis of Diamond Thin Films for Applications in High Temperature Electronics." University of Cincinnati / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1145630189.
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Tsavdaris, Nikolaos. "Incorporation d'azote et stabilité des polytypes de la croissance en phase gazeuse de monocristaux de SiC." Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GRENI011.
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Le carbure de silicium est l'un des semi-conducteurs les plus importants et les plus répandus dans les appareils électroniques de puissance. Du fait de la demande croissante d'électronique à haut rendement, bas coût et économe en énergie, il est nécessaire d'améliorer les propriétés des semi-conducteurs monocristallins. Cela demande une meilleure compréhension des phénomènes impliqués dans le procédé de croissance de ces matériaux. Cette thèse présentera de nouvelles perspectives sur deux sujets majeurs dans le domaine de la croissance en phase gazeuse de monocristaux de SiC. Dans un premier temps, le procédé de croissance utilisé dans notre laboratoire a été développé dans le but d'améliorer la qualité et la taille des cristaux de SiC obtenus. Une géométrie permettant la croissance sans contact et reproductible de monocristaux de SiC a été obtenue. La nucléation et la propagation des instabilités structurelles (inclusions de polytype étranger) apparaissant lors de la croissance ont été étudiés de façon continue. Deux critères spécifiques doivent être réunis pour qu'un polytype étranger puisse nucléer. Une fois le point de nucléation localisé, la propagation du polytype étranger dans le volume du cristal peut être appréhendée. Lorsque la stabilisation et déstabilisation des polytypes de SiC ont été mieux comprises, une tentative a été faite pour stabiliser la croissance du polytype 15R-SiC. L'objectif final, les paramètres de croissance susceptibles de renforcer la croissance préférentielle de 15R-SiC, a été mis en évidence. Enfin, l'incorporation d'azote pendant la croissance en phase gazeuse de monocristaux a été étudiée. En effet, aucune description détaillée n'existe pour l'incorporation d'azote dans le SiC, bien que ce soit le dopant le plus couramment utilisé. Notre contribution à cet effort porte sur l'étude de la concentration d'azote dans les cristaux obtenus en fonction de différents paramètres de croissance. Compte tenu des mécanismes d'adsorption/désorption à la surface de croissance, un effort a été fait pour expliquer les tendances obtenues expérimentalementSilicon Carbide is one of the most important and widely used semiconductors for power electronic devices. Due to the increasing demand for high efficiency, low cost and energy saving electronics, further improvement of the properties of single crystal semiconductors is needed. That requires a better understanding of the phenomena involved in the growth process of these materials. This thesis will bring some new insight into two main topics at the field of SiC bulk growth from the vapor phase. Initially, the growth process used in our laboratory was developed in order to improve the quality and the size of the grown SiC crystal. A geometry that allows the contactless and reproducible growth of SiC single crystals was obtained. Continuously, we investigated the nucleation and propagation of structural instabilities (foreign polytype inclusions) that appear during growth. Two specific criteria must be fulfilled for a foreign polytype to be nucleated. Once the nucleation point is located, the propagation of the foreign polytype in the volume of the grown crystal can be comprehended. Once the stabilization or destabilization of the SiC polytypes was better perceived, an attempt was made to stabilize the growth of the 15R-SiC polytype. As a final objective, the growth parameters that could preferentially enhance the growth of the 15R-SiC are highlighted. Last, nitrogen incorporation during bulk growth from the vapor phase was studied. Indeed as the most commonly used dopant, no full description exists for the incorporation of nitrogen in SiC. We contribute to this effort by exploring the nitrogen concentration in the grown crystals as a function of various growth parameters. Considering the adsorption/desorption mechanisms at the growing surface, effort was given to explain the experimentally obtained trends
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Hsieh, Yu-Yun. "Nanostructured Carbon-Based Composites for Energy Storage and Thermoelectric Applications." University of Cincinnati / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ucin157322525150617.
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Murdock, Adrian T. "Chemical vapour deposition growth of large-area graphene on metals." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:07fa91ef-0d61-4086-a7d8-a53537dcb54b.
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Graphene has unrivalled properties and is heralded as a revolutionary material for the 21st century. Chemical vapour deposition (CVD) on metals is a promising method to produce large-area graphene. Controlling the properties of CVD graphene is vital for its integration in a wide-range of future applications. Many factors can influence the CVD growth of graphene and its properties, therefore further investigations will be beneficial to fully understand and control this technique. In this thesis I expand the knowledge about the growth of pure and heteroatom-doped graphene by low pressure chemical vapour deposition (LPCVD) and atmospheric pressure chemical vapour deposition (APCVD) on commercially available Cu and Pt foils. Using a range of characterisation techniques, I investigate the influence of the substrate’s properties and the synthesis conditions on the growth of graphene, in pursuit of improved, controlled or optimised production, which can promote high quality, large-area, single-layer graphene, or other as desired. By characterising the topography, surface roughness, crystallographic orientations, and chemical composition of six Cu foils, I find that their properties vary greatly and this influences the growth of CVD graphene. I elucidate that the commonly used 99.8 % Alfa Aesar Cu foil has a surface coating composed of calcium, chromium, and phosphorus, which detrimentally influences graphene growth. Cleaning Cu foils with CH3COOH is shown to reduce the concentration of surface contaminants, consequently reducing the nucleation density and increasing the growth rate of CVD graphene. I also demonstrate that the shape, orientation, edge-geometry and thickness of CVD graphene domains can be controlled by the Cu crystallographic orientations. Single layer LPCVD graphene domains align with zigzag edges parallel to a single <101> direction on Cu{111} and Cu{101}, while bilayer domains align to two directions on Cu{001}. Hexagonal APCVD domains also preferentially align with edges parallel to the <101> direction(s). This discovery resolves a key challenge of controlling the orientation of individual graphene domains and opens a new avenue for tailored production of large-area CVD graphene with improved properties. By controlling the synthesis conditions of APCVD graphene on Pt foils I optimise production of ~0.5 mm single layer graphene domains with reduced nucleation density and increased growth rate of ~100 μm/min by synthesis at 1150°C, a higher temperature than previously reported. The absence of large, hexagonal, single-crystal domains on pristine Pt foil, and observation of a reaction between quartz and Pt that promotes hexagonal domains, suggests that a silicon or platinum silicide surface layer may be advantageous for improved growth of graphene. Finally, I demonstrate that the dopant concentration of nitrogen-doped graphene is increased at lower synthesis temperatures and higher NH3 concentration, up to 1.3 %, but with an associated decrease in the growth rate. Direct visualisation, elemental confirmation, and electronic characterisation of individual nitrogen atoms is shown for the first time using aberration corrected scanning transmission electron microscopy and electron energy loss spectroscopy. Boron-doped graphene is also synthesised. The implications of these findings, and many additional minor contributions, are wide-ranging and of considerable importance for the future understanding of CVD growth of graphene on metals, and more generally for the advancement of scientific knowledge for manufacturing large-area graphene. Collectively, these discoveries represent a significant body of work that can improve the efficiency of production and assist with controlling the properties of large-area CVD graphene.
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Youssef, Laurène. "Développement par procédé plasma de couches minces de type TiO2 dopé à l'azote pour la production d'hydrogène par photo-électrolyse de l'eau sous lumière solaire." Thesis, Montpellier, 2018. http://www.theses.fr/2018MONTS133/document.
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Le couplage direct de la séparation et de la photo-catalyse en utilisant des membranes à base de dioxyde de titane, est une approche intéressante habituellement appliquée dans les dispositifs de traitement de l'eau, et récemment envisagée pour d’autres applications, telle que la production d’hydrogène par photo-électrolyse de l’eau. En effet, le dioxyde de titane (TiO2) est bien connu pour ses propriétés photo-catalytiques. En outre, s’il est immobilisé sur support membranaire plutôt qu’utilisé en suspension, son intégration en procédé de séparation est facilitée, sans compter les gains apportés au procédé en termes de compacité, d’intégrité et de capacité séparative. Pour une telle application, des cellules originales sous forme de multicouches sont requises. Certains systèmes sont décrits dans la littérature mais aucun d’entre eux n’est réellement intégré (c’est-à-dire basé sur une géométrie de type multicouche micro-architecturée), ni formé de couches minces obtenus par procédés plasma. Or les procédés plasma sont généralement compétitifs pour l’obtention de systèmes multicouches de hautes intégrité et compacité. Dans le cadre de récents travaux menés à l’IEM, différents types de couches minces ont été préparés par PECVD (Plasma Enhanced Chemical Vapor Deposition), à savoir des films de TiO2 connus pour leurs propriétés photo-catalytiques et des membranes phosphoniques de conduction protonique avérée. En outre, des films minces de platine efficaces pour la réduction catalytique des protons en hydrogène peuvent être également déposés par un autre procédé plasma, la pulvérisation cathodique. Au cours de ce travail de thèse, des films de TiO2 obtenus par PECVD Basse Fréquence sont optimisés en termes d’activité photo-catalytique et de propriétés séparatives; cette optimisation, qui concerne le dopage à l’azote du TiO2 (permettant le déplacement de la bande interdite de la région UV vers la région visible), est le premier objectif de ce projet de thèse. Les films minces sont caractérisés du point de vue de leurs propriétés structurales et fonctionnelles. Le second objectif de la thèse est de montrer l’intérêt de ces films de TiO2 dans la production/séparation d’hydrogène par voie solaire. Dans ce but, la photo-activité des films dans le noir, sous UV et sous visible est étudiée dans une cellule mono-compartiment où les deux électrodes baignent dans un électrolyte liquide. Des études électrochimiques plus poussées en présence d’une membrane électrolyte commerciale et d’une cathode de platine (dont les caractérisations en propre sont portées en annexes de ce travail), sont aussi abordées. Le dernier objectif de cette thèse est le transfert de la technologie des procédés plasma de l’Institut Européen des Membranes de l’Université de Montpellier vers le Laboratoire Chimie-Physique des Matériaux de l’Université Libanaise. Les détails de l’installation du réacteur au Liban font l’objet du dernier chapitre de la thèse ainsi que les résultats des premiers tests de dépôt sur la base de conditions opératoires précédemment optimisées à l’Institut Européen des MembranesDirect coupling of separation and photo-catalysis using membranes based on titanium dioxide, is an interesting approach usually applied in water treatment devices, and recently considered for other applications, such as hydrogen production by water photo-electrolysis. Indeed, titanium dioxide (TiO2) is well-known for its photo-catalytic properties. In addition, if it is immobilized on membrane supports rather than used in suspensions, its integration in the separation process is facilitated and some advantages of the process in terms of compactness, integrity and separation capacity are provided. For such an application, original multilayered cells are required. Some systems are described in the literature but none of them is truly integrated (that is to say based on a micro-architecture geometry of multi-layer type) or formed of thin layers obtained by plasma processes. Now plasma processes are generally competitive for obtaining multilayered systems with high integrity and compactness. As part of recent works at IEM, various types of thin films were prepared by PECVD (Plasma Enhanced Chemical Vapor Deposition) to include TiO2 films known for their photo-catalytic properties and phosphonic acid membranes with average protons conductivity. In addition, effective platinum thin films for the protons catalytic reduction into hydrogen could also be deposited by another plasma process, sputtering. In this work, TiO2 films obtained by Low Frequency PECVD are optimized in terms of photo-catalytic activity and separation properties; this optimization, regarding the nitrogen doping of TiO2 (for the band gap shifting from the UV region to the visible region), is the first objective of this thesis project. The thin films structural and functional properties are characterized.The second aim of this thesis is to demonstrate the competitiveness of these films for the Hydrogen production/separation by solar energy. To this end, the layers photo-response has been tested in the dark, under UV and under visible light in a mono-compartment cell where both electrodes are immersed in a liquid electrolyte. Further studies integrating the TiO2 layers in contact with a commercial electrolyte membrane and a platinum counter-electrode (whose characterizations are presented in annexes), are also performed. The last aim of this work is the Plasma technology transfer from the European Membrane Institute of University of Montpellier to the Laboratory of Physical Chemistry of Materials of Lebanese University. The installation and configuration details are presented in the last chapter as well as the results of the first depositions based on operating conditions already optimized at European Membrane Institute
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Souza, Juliana dos Santos de. "Estudo da atividade fotocatalítica de nanotubos de titanatos dopados com nitrogênio via técnica de ressonância paramagnética eletrônica." reponame:Repositório Institucional da UFABC, 2016.
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Orientador: Prof. Dr. Wendel Andrade AlvesTese (doutorado) - Universidade Federal do ABC. Programa de Pós-Graduação em Ciência e Tecnologia/Química, 2016.
Nanotubos de titanato tem atraído muita atenção devido a suas propriedades únicas, que permitem sua aplicação em catálise, fotocatálise, e no desenvolvimento de dispositivos de conversão de energia. No entanto, esses materiais são capazes de absorver somente radiação UV, o que torna necessária sua sensibilização frente à radiação visível que pode ser feito através da dopagem ou sensibilização com corantes. Neste trabalho, nanotubos de titanato foram preparados através da síntese hidrotérmica alcalina e dopados usando um método de troca iônica seguida por uma etapa de calcinação a 200 ºC e 400 ºC, resultando em duas séries de catalisadores: nanotubos de titanato dopados com nitrogênio (NTiNTs) e nanotubos de dióxido de titânio dopados com nitrogênio (NTiO2NTs), respectivamente. A caracterização destes materiais revelou que a temperatura de calcinação afeta a intensidade de cor, área superficial, energia band gap e natureza da espécie de nitrogênio dopante. Os catalisadores NTiO2NTs reúnem as propriedades que os qualificam como melhores fotocatalisadores, sendo capazes de degradar de 1,8% (m/m, massa de corante degradado por 100g de catalisador) a 2,9%, enquanto os NTiNTs foram capazes de degradar somente de 0,17%mg mg-1 a 0,60%. Os catalisadores NTiNTs e NTiO2NTs também foram sensibilizados com ftalocianina de cobre(II) tetracarboxilada. Observou-se que a sensibilização não afeta a forma nem a estrutura cristalina dos nanotubos, no entanto, ela promove alterações nas propriedades superficiais levando a interações diferenciadas entre os tubos. Esses materiais foram aplicados na degradação de rodamina B através de mecanismos de fotocatálise e catálise mediada por H2O2. Observou-se que os catalisadores sensibilizados apresentam eficiência fotocatalítica cerca de 50% menor do que os materiais não sensibilizados. No caso da catálise mediada por H2O2 a sensibilização aumenta a atividade catalítica, podendo atingir 100% de eficiência. Por fim, foram desenvolvidos novos eletrodos multi-hierárquicos baseados em filmes de nanobastões de óxido de zinco (ZnONR) decorados com nanotubos de titanato, utilizando glicina como uma ponte para promover o aumento da interação entre as estruturas. Estes eletrodos foram aplicados como fotoanodos no desproporcionamento fotoeletroquímica da água, gerando O2 e H2. Os resultados mostraram que a heterojunção dos dois óxidos metálicos leva a um aumento da eficiência fotoeletroquímica. Desse modo, os eletrodos multihierárquicos são capazes de produzir correntes de geração de O2 de 0,90 mA cm-2 (a 1,23 V vs ERHE), enquanto os eletrodos de ZnONR puros produzem 0,45 mA cm-2. O potencial de evolução de O2 também diminui de 0,8 V (vs ERHE) para eletrodos de TiNTs para 0 V no caso dos eletrodos multi-hierárquicos.
Titanate nanotubes have attracted much attention due do their unique properties which allow their application in catalysis, photocatalysis and energy conversion devices development. However, this material is able to absorb only UV radiation making necessary its sensibilization toward visible radiation that can be done through doping or dye sensibilization. In this work, titanate nanotubes were prepared through alkaline hydrothermal synthesis and doped using an ion exchange methodology followed by a calcination step at 200 ºC and 400ºC, resulting in two series of catalysts: nitrogen doped titanate nanotubes (NTiNTs) and nitrogen doped titanium dioxide nanotubes (NTiO2NTs), respectively. The characterization of these materials revealed that the calcination temperature affects color intensity, surface area, band gap energy and nature of doping nitrogen species. The NTiO2NTs catalysts gather the properties that qualify them as better photocatalysts, being capable of degrading from 1,8% (m/m, degraded dye mass by 100 g of catalyst) to 2,9%, whereas the NTiNTs are capable of degrading only 0,17% to 0,60%. The catalysts NTiNTs and NTiO2NTs were also sensitized with tetracarboxylate cooper(II) phthalocyanine. It has been observed that the sensibilization does not affect the morphology or crystalline structure of the nanotubes; however, it promotes changes on the surface properties leading to differentiated interactions between the tubes. These materials were applied on rhodamine B degradation through mechanisms of photocatalysis and catalysis mediated by H2O2. It was observed that the sensibilized catalysts exhibit photocatalytic efficiency of about 50% lower than nonsenbilized materials. In the case of catalysis mediated by H2O2 the sensibilization increases catalytic activity, which can reach 100% of efficiency. Finally, new multihierarchical electrodes were developed, based on zinc oxide nanorods (ZnONR) films decorated with titanate nanotubes, using glycine as a bridge to promote the increasing of the interaction between the structures. These electrodes were applied as photoanodes for photoelectrochemical water splitting, producing O2 e H2. The results show that the heterojunction of the two metal oxides leads to an increasing of the photoelectrochemical efficiency. Thus, the multi-hierarchical electrodes are capable of producing O2 evolution currents of 0.90 mA cm-2 (at 1.23 V vs ERHE), whereas the pure ZnONR electrodes produce 0.45 mA cm-2. The O2 evolution potential also decreases from 0.8 V (vs ERHE) for TiNTs electrodes to 0V for the multi-hierarchical electrodes.
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Valour, Arnaud. "Synthèse d'oxyde de zinc dopé azote sous formes de poudre et de couche mince : caractérisation du type de semiconductivité." Thesis, Rennes 1, 2017. http://www.theses.fr/2017REN1S014/document.
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Cette thèse fait suite à des travaux ayant permis, de manière non reproductible, la stabilisation de l’oxyde de zinc de type-p (p-ZnO:N) sur une période de plus de deux ans par décomposition de ZnO2 sous flux de NH3. L’objectif de ces travaux était de maîtriser de manière reproductible la synthèse de p-ZnO:N sous formes de poudre, puis de couche mince, dans l’optique de réaliser des homojonctions p-ZnO:N/n-ZnO ayant de potentielles applications dans le domaine de l’optoélectronique. Dans ce but, différents paramètres de la synthèse ayant permis initialement l’obtention de p-ZnO:N fortement lacunaire en zinc (20%) ont été étudiés sans aboutir de nouveau à la stabilisation du caractère-p. La formation in-situ d’impuretés NO3- mise en évidence conduit à une ambiguïté quant à l’origine du type-p dans notre matériau. Parallèlement, une nouvelle voie de synthèse a été mise en place, en utilisant l’approche colloïdale, permettant d’obtenir des nanocristaux de ZnO inférieurs à 10 nm facilement convertibles en nanoparticules de ZnO2 par simple traitement avec une solution diluée d’H2O2 à température ambiante. Le matériau final ZnO:N est obtenu après nitruration sous flux d’ammoniac à 250°C. Ces résultats ont été efficacement transposés à la réalisation de couches minces (CM) de ZnO:N par dip-coating, mais les mesures Mott-Schottky ont également révélé une conductivité de type-n pour tous les échantillons. Enfin, les résultats préliminaires des calculs théoriques menés en parallèle de cette thèse nous ont amenés à reconsidérer les conditions de synthèse pour favoriser l'insertion de NH3 / NH4+ lors de la préparation des échantillons dans la quête de p-ZnO:NCette thèse fait suite à des travaux ayant permis, de manière non reproductible, la stabilisation de l'oxyde de zinc de type-p (p-ZnO:N) sur une période de plus de deux ans par décomposition de ZnO2 sous flux de NH3. L'objectif de ces travaux était de maîtriser de manière reproductible la synthèse de p-ZnO:N sous formes de poudre, puis de couche mince, dans l'optique de réaliser des homojonctions p-ZnO:N/n-ZnO ayant de potentielles applications dans le domaine de l'optoélectronique. Dans ce but, différents paramètres de la synthèse ayant permis initialement l'obtention de p-ZnO:N fortement lacunaire en zinc (20%) ont été étudiés sans aboutir de nouveau à la stabilisation du caractère-p. La formation in-situ d'impuretés NO3- mise en évidence conduit à une ambiguïté quant à l'origine du type-p dans notre matériau. Parallèlement, une nouvelle voie de synthèse a été mise en place, en utilisant l'approche colloïdale, permettant d'obtenir des nanocristaux de ZnO inférieurs à 10 nm facilement convertibles en nanoparticules de ZnO2 par simple traitement avec une solution diluée d'H2O2 à température ambiante. Le matériau final ZnO:N est obtenu après nitruration sous flux d'ammoniac à 250°C. Ces résultats ont été efficacement transposés à la réalisation de couches minces (CM) de ZnO:N par dip-coating, mais les mesures Mott-Schottky ont également révélé une conductivité de type-n pour tous les échantillons. Enfin, les résultats préliminaires des calculs théoriques menés en parallèle de cette thèse nous ont amenés à reconsidérer les conditions de synthèse pour favoriser l'insertion de NH3 / NH4+ lors de la préparation des échantillons dans la quête de p-ZnO:N
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Borges, Karen Araújo. "Síntese, otimização e caracterização da atividade fotocatalítica de TIO2 dopado com nitrogênio." Universidade Federal de Uberlândia, 2015. https://repositorio.ufu.br/handle/123456789/17525.
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Coordenação de Aperfeiçoamento de Pessoal de Nível SuperiorThe optimization of the synthetic route of titanium dioxide nanoparticles doped with nitrogen was carried out in order to obtain photocatalysts with improved photocatalytic activity. Thereby, from the synthesized photocatalysts was possible to reach about 100% discoloration and 64% mineralization of Ponceau 4R (P4R) dye. Both doped (with largest and smallest photocatalyitc activity) and undoped catalysts were analyzed by X-ray diffraction showing the predominance of the crystalline anatase phase. Besides, using the Rietveld method, the results showed 17.3% of brookite phase in the undoped oxides. By further analysis of diffuse reflectance spectroscopy was observed that doped catalysts presented slight shift on absorption band to the visible region, highlighting the best photocatalyitc activity of the oxide with a band gap of 3,29 eV. This oxide (K1) exhibited specific area of 63.03 g/m2 while the oxide with lower photocatalytic activity (K2) exhibited a specific area of 12.82 g/m2. The Raman spectroscopy analysis showed that doped samples are more ordered than no doped, and vibrational modes related to nitrogen was not observed. Infrared spectra showed that calcination of the doped oxides leads to considerable loss in nitrogen content, and this is corroborated by the XPS measurements. Photocatalytic assays were carried out on laboratory scale using K1 catalyst in order to optimize the mineralization of P4R. Thus, the substrate concentration, catalyst concentration and pH of reaction medium were evaluated and the best result was 85% mineralization using 15 mg/L of P4R, 100 mg/L of catalyst and pH 6.4. Additional photocatalytic tests were conducted under solar radiation showing that doping increases photocatalytic activity under UV-A and visible irradiation, since 600 kJ of accumulated UV-A radiation (referring to 9 minutes of reaction time in bench scale) proved to be enough to reach 100% mineralization of dye using doped catalyst against 77% mineralization using undoped catalyst.
Com a finalidade de obter um fotocatalisador com atividade fotocatalítica melhorada otimizou-se a rota de síntese para a obtenção de nanopartículas de dióxido de titânio dopado com nitrogênio. A partir deste procedimento foi possível obter um fotocatalisador capaz de descolorir em 100% o corante Ponceau 4R (P4R), e mineralizar 64% sua carga orgânica. Os catalisadores que apresentaram a maior e menor atividade fotocatalítica, e o óxido não dopado foram analisados por difração de raios-X, que mostrou a predominância da fase cristalina anatase nos óxidos dopados. Além disso, no óxido não dopado, além da fase anatase constatou-se, usando o método de Rietveld, a presença de 17,3 % da fase broquita. Por espectroscopia de reflectância difusa observou-se, para os óxidos dopados, um pequeno deslocamento da absorção de luz para a região do visível, com destaque para o óxido com a maior atividade fotocatalítica, que apresentou um band gap de 3,29 eV. Este óxido, (K1), apresentou área específica de 63,03 g/m2, enquanto que para o de menor atividade fotocatalítica, (K2), foi de 12,82 g/m2. Por espectroscopia Raman verificou-se que as amostras dopadas são mais ordenadas que a amostra não dopada. Por outro lado, não foram observados modos vibracionais relacionados ao nitrogênio. Os espectros de infravermelho mostraram que a calcinação dos óxidos dopados causa uma perda considerável no conteúdo de nitrogênio, o que é confirmado por medidas de XPS. Para o catalisador K1 foram realizados experimentos em escala de laboratório com o intuito de otimizar as condições reacionais para a mineralização do P4R. Foram avaliados o efeito da concentração do substrato, concentração do catalisador e pH do meio reacional, onde os melhores resultados (85% de mineralização) foram obtidos utilizando-se 15 mg/L do P4R, 100 mg/L do catalisador, em pH 6.4. Os testes fotocatalíticos feitos sob irradiação solar evidenciaram que a dopagem amplia a atividade fotocatalítica sob irradiação no UVA e visível, já que com 600 kJ m-2 (equivalente a 9 minutos de reação nos experimentos em escala de bancada) de radiação UV-A acumulada, 100% do corante foi mineralizado com o catalisador dopado, e apenas 77% com o seu similar não dopado.
Doutor em Química
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Polteau, Baptiste. "Étude de semi-conducteurs de type p nanostructurés à base de métaux de transition pour une application en DSSC-p." Thesis, Rennes 1, 2016. http://www.theses.fr/2016REN1S046/document.
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Dans le but d'améliorer le rendement des cellules à colorant de type p (DSSC-p), ces travaux s'attachent à la synthèse et la caractérisation de matériaux semi-conducteurs de type p (SCs-p) sous forme de nanoparticules. En ce sens, des SCs-p répondant à un cahier des charges (bande de valence basse en énergie, grande surface spécifique, bon conducteur et bonne transparence) ont été étudiés. Dans ce cadre, une stratégie a été développée pour améliorer les propriétés de NiO (l'actuel matériau de référence) en optimisant sa nanostructuration, sa forte non-stœchiométrie en nickel et par son dopage à l'azote, paramètres tous favorables à la stabilisation de la valence mixte Ni3+/Ni2+, origine de la conductivité de type p. Cette longue étude a été initiée à partir d'un précurseur de nickel original nanostructuré Ni3O2(OH)4, à forte valence mixte Ni3+/Ni2+. La décomposition sous air et sous ammoniac de ce précurseur à basse température (250 °C) a permis de préparer Ni1-xO nanostructuré, fortement non-stœchiométrique (VNi = 25 %), de grande surface spécifique (240 m2.g-1) et dopé azote (NiO:N). De plus, deux matériaux non oxydes à structure delafossite, que sont les carbodiimides de nickel (NiNCN) et de manganèse (MnNCN) ont été préparés et caractérisés comme de nouveaux semi-conducteurs de type p, permettant de monter la première DSSC-p à base de NiNCNTo improve the performances of p-Dye Sensitized Solar Cell (p-DSSC), this thesis work focuses on the synthesis and the characterization of p-type semiconductors (p-SCs) nanomaterials. These p-SCs with some specifications (low energy valence band, high specific surface area, high conductivity and transparency) were thoroughly studied. In this context, a strategy was developed to improve the NiO nanoparticles properties (commonly used as a reference) with higher nickel non-stoichiometry and nitrogen doping to promote the stabilization of the Ni3+/Ni2+ mixed valence (origin of the p-typness). This study was initiated with a nanostructured mixed valent Ni3O2(OH)4 precursor. Its thermal decomposition in air and ammonia at low temperature (250 °C) allows the formation of nanostructured Ni1-xO with a large amount of Ni vacancies (VNi = 25 %), a high specific surface area (240 m2.g-1) and a nitrogen doping (NiO:N). Moreover, two non-oxides materials with delafossite structure type, namely - nickel carbodiimide (NiNCN) and manganese carbodiimide (MnNCN) - were prepared and characterized as new p-type semiconductors. Thus, the first p-DSSC with NiNCN material was built with success
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Yang, Weilu. "Electrochemical advanced oxidation processes for emerging organic contaminants removal with graphene-based modified carbon felt electrode." Thesis, Paris Est, 2019. http://www.theses.fr/2019PESC2025.
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Grâce au développement continu de technologies d'analyse environnementale, certains produits chimiques, qui sont reconnus être nocif, ont récemment attiré l'attention, puisqu'ils constituent un menace pour l'environnement et la santé publique.Parmi ces polluants émergent, les produits pharmaceutiques et de soins personnels (PPSP)sont devenus le cibles dela recherche internationale. La chine est le plus grand producteur et le marché des médicaments dans le monde. Avec le développement de l'économie sociale et l'amélioration du niveau de vie de la population, de la production et de l'utilisation de divers PPSP présents en chine augmente rapidement. Par comparaison avec les polluants classiques, ces contaminants émergents sont généralement difficiles à analyser en raison de la limitation de technologies analytiques et de sa faible concentration dans les eaux naturelles.Les usines traditionnelles de traitement des eaux usées ne peuvent pas éliminer efficacement ces produits. La recherche sur l'évaluation des risques et le contrôle des nouveaux contaminants émergents, en chine constitue actuellement un grand défi. Il est donc essentiel de renforcer la recherche sur l'évaluation des risques pour l'environnement et les technologies de traitement efficaces pour éliminer ces polluants émergents. Les procédés d'oxydation avancée (POA) constituent une technologie de traitement efficace et ont été largement utilisés dans le traitement des polluants organiques réfractaires tels que les la destruction des contaminants émergents en milieu aqueux à cause de leur forte pouvoir d'oxydation permettant une minéralisation in situ des polluants. Le graphite, comme un nouveau type de matériau carbone adsorbant, est devenue un matériau d'électrode pour le traitement de la pollution due à son excellente conductivité et surface spécifique très élevée. Toutefois, son application dans les AOPs n'a pas été largement étudié et le mécanisme d'oxydation n'a pas été expliquée de manière systématique. Par conséquent, ce travail présent une étude détaillée sur le rôle des électrodes graphite modifiées dans les procédés électrochimiques d'oxydation avancée (PEOA) avec la préparation électrochimique des électrodes modifiées au graphène par exfoliation, et leur application dans le PEOA "électro-Fenton" (EF) pour le traitement des contaminants émergents. Ainsi le cathode en feutre de carbone modifiée au graphène a permis de d'éliminer différents contaminants émergents sans utilisation d'ions ferreux (catalyseur du procédé électro-Fenton) car les radicaux hydroxyles sont générés à travers d'un procédure catalytique grâce à la dopage du graphène à l'azote. Ensuite les cinétiques de dégradation et de minéralisation ainsi que les mécanismes d'oxydation de différents contaminants émergents ont été exploréesIn recent years, with the continuous development of environmental analysis technologies, some chemicals, which have long been recognized but recently attracted attention, have been continuously entering the environment and threatening human health and ecological environment. The emergence of these new pollutants have attracted wide attention. Among them, pharmaceuticals and personal care products (PPCPs) have become international research hotspots. China is the largest medicine producer and market in the world. With the development of social economy and the improvement of people's living standards, the production and use of various PPCPs in China are increasing rapidly. Compared with the traditional pollutants, the new emerging contaminants are generally difficult to be analyzed due to the limitation of analytical technologies and its low concentration in water. The traditional sewage treatment plants can not achieve efficient degradation and removal effects. The research on risk assessment and control of new emerging contaminants in China is still a big challenge. It is necessary to strengthen the research on potential environmental risk assessment and efficient treatment technology. Advanced oxidation processes (AOPs), as an efficient pollutant treatment technology, has been widely used in the treatment of refractory organic pollutants such as new emerging contaminants in water because of its strong oxidation ability, which can effectively degrade and mineralize pollutants in water. Graphene, as a new type of carbon material, has become an efficient adsorbent and catalyst for pollution treatment due to its excellent conductivity and high specific surface area. However, its application in AOPs has not been widely reported and its mechanism has not been systematically explained. Based on this, this paper studied the role of graphene modified electrodes in electrochemical advanced oxidation processes (EAOPs) with the preparation of graphene by electrochemical exfoliation, application of graphene modified electrodes to electrochemical Fenton (EF) process for the degradation of new emerging contaminants; the construction of in-situ iron-free EAOPs with cathodes modified with nitrogen-doped graphene for abatement of new emerging contaminants and the mechanism of highly efficient catalysis with nitrogen-doped graphene have been explored
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Xu, Zhenxin. "Development of new macroscopic carbon materials for catalytic applications." Thesis, Strasbourg, 2019. http://www.theses.fr/2019STRAF005/document.
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De nos jours, les matériaux carbonés macroscopiques font face à un nombre croissant d'applications en catalyse, soit en tant que supports, soit directement en tant que catalyseurs sans métal. Cependant, il reste difficile de développer un support de catalyseur hiérarchisé à base de. carbone ou un catalyseur utilisant un procédé de synthèse beaucoup plus simple. À la recherche de nouveaux matériaux carbonés structurés pour la catalyse hétérogène, nous avons exploré le potentiel du feutre de carbone / graphite du commerce (FC / FG). Le but du travail décrit dans cette thèse a été le développement du monolithe FG et FC en tant que catalyseur sans métal pour les réactions d’oxydation en phase gazeuse et en tant que support de catalyseur, notamment pour le palladium, pour les réactions d’hydrogénation en phase liquide, et leur rôle dans la performance de réaction de ces catalyseurs. En raison de leur surface de chimie inerte avec une mouillabilité inappropriée, une telle étude avait pour condition d'activer celles d'origine. Par conséquent, des FG et des FC modifiés bien arrondis ont été synthétisés avec des propriétés physico-chimiques adaptées par une série de procédés de traitement chimique, tels que l'oxydation, l'amination, la thiolation, le dopage à l'azote et au soufre. L’oxydation partielle du sulfure d’hydrogène en soufre élémentaire et l’hydrogénation sélective du cinnamaldéhyde α, β-insaturé, en tant que réactions sensibles à l’effet des propriétés du catalyseur sur l’activité et la sélectivité, combinées à des techniques de caractérisation, ont été choisis pour étudier l’effet de la matériaux carbonés sur le comportement catalytiqueNowadays, macroscopic carbon materials are facing an increasing number of applications in catalysis, either as supports or directly as metal-free catalysts on their own. However, it is still challenging to develop hierarchical carbon-based catalyst support or catalyst using a much simple synthesis process. In the quest for novel structured carbon materials for heterogeneous catalysis we explored the potential of commercial carbon/graphite felt (CF/GF). The aim of the work described in this thesis has been the development of GF and CF monolith as metal-free catalyst for gas-phase oxidation reactions and as catalyst support, notably for palladium, for liquid-phase hydrogenation reactions, and their roles in the reaction performance of these catalysts. Due to their inert chemistry surface with inappropriate wettability, a prerequisite for such a study was to activate the origin ones. Therefore, well-rounded modified GFs and CFs were synthesized with tailored physic-chemical properties by a series of chemical treatment processes, such as oxidation, amination, thiolation, nitrogen- and sulfur-doping. The partial oxidation of hydrogen sulfide into elemental sulfur and selective hydrogenation of α, β-unsaturated cinnamaldehyde, as the sensitive test reactions to the influence of the catalyst properties on activity and selectivity, combined with characterization techniques, were chosen to investigate the effect of functionalized carbon materials on the catalytic behavior
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Moumaneix, Lilian. "De l’élaboration de matériaux graphéniques tridimensionnels dopés à l’azote : vers des catalyseurs pour l’électroréduction de l’oxygène sans platine." Electronic Thesis or Diss., Université de Lorraine, 2020. http://www.theses.fr/2020LORR0081.
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Le stockage de l’énergie sous la forme de dihydrogène suscite un intérêt grandissant dans la communauté scientifique et les industries du secteur de l’énergie et du transport. Les piles à combustible à membrane échangeuse de protons (PEMFC) permettent de convertir ce gaz en électricité sans rejets nocifs, à des températures peu élevées. Les catalyseurs actuels sont majoritairement constitués de nanoparticules de platine, déposées sur un matériau carboné microporeux. Or, ce métal noble est source de problèmes environnementaux et sociétaux, et son approvisionnement est soumis à des tensions et aléas géopolitiques. Ces travaux de thèse explorent la possibilité d’utiliser des matériaux alternatifs sans métaux. Largement étudiés dans la littérature, les matériaux carbonés dopés à l’azote possèdent une activité catalytique pour la réaction de réduction de l’oxygène (ORR), celle-ci étant la plus limitante dans les PEMFC. Une méthode d’élaboration s’appuyant sur une réaction solvothermale entre un alcool et du sodium, suivie d’un traitement de pyrolyse, a été mise au point, permettant l’obtention de matériaux graphéniques dopés, présentant un fort caractère tridimensionnel et une porosité très développée. L’étude de la réaction solvothermale entre la 1-(2-hydroxyéthyl)pipéridine et le sodium a permis de donner une description du déroulement de la réaction, en se focalisant sur la composition de l’atmosphère du réacteur solvothermal pendant la réaction, et sur la caractérisation du composé solvothermal solide. De plus, l’influence des conditions de pyrolyse sur le matériau final a été suivie à l’aide de techniques de caractérisation complémentaires et multi-échelles, permettant d’élaborer des matériaux de bonne qualité structurale et de surface spécifique élevée. L’activité catalytique des matériaux graphéniques dopés a été prouvée dans une PEMFC. Des densités de puissance électrique supérieures à 3 mW.cm-2 ont ainsi été atteintes. Plusieurs paramètres contribuant à l’amélioration de l’activité catalytique vis-à-vis de l’ORR ont été identifiés, permettant de mieux cibler les aspects futurs sur lesquels progresserThe storage of energy in the form of dihydrogen is attracting growing interest in the scientific community as well as in the energy and transport industries. Proton exchange membrane fuel cells (PEMFC) convert this gas into electricity without harmful emission, at relatively low temperatures. Nowadays, catalysts are mainly made up of platinum nanoparticles, deposited on a microporous carbon material. However, this noble metal is a source of environmental and societal problems, and its supply is subject to geopolitical tensions and vagaries. This thesis work explores the possibility of using alternative materials without metals. Widely studied in the literature, carbon materials doped with nitrogen atoms have a catalytic activity for the oxygen reduction reaction (ORR), this reaction being the most limiting in PEMFCs. An elaboration method based on a solvothermal reaction between an alcohol and sodium, followed by a pyrolysis treatment, has been developed, yielding N-doped graphenic materials with a pronounced three-dimensional aspect and a very developed porosity. The study of the solvothermal reaction between 1-(2-hydroxyethyl)piperidine and sodium allowed to give a description of the reaction mechanism, by focusing on the analysis of the atmosphere composition within the solvothermal reactor during the reaction, and on the characterization of the solid solvothermal product. In addition, the influence of the pyrolysis conditions on the final material was studied using complementary and multi-scale characterization techniques, permitting to elaborate materials with good structural qualities and high specific surfaces. The catalytic activity of doped graphenic materials has been proven inside a PEMFC. Electrical power densities greater than 3 mW.cm-2 have been reached. Several parameters contributing to the improvement of the catalytic activity towards the ORR were identified, allowing to better target the future aspects on which to progress
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Lagrange, Jean-Pierre. "Contribution à l'étude du dopage bore, azote et phosphore dans le diamant." Université Joseph Fourier (Grenoble), 1997. http://www.theses.fr/1997GRE10210.
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Le diamant est un semi-conducteur a large bande interdite (5. 4 ev) tres prometteur en electronique a haute temperature et de forte puissance. Cependant, son utilisation est limitee par l'absence d'un dopage de type n. Nous avons etudie dans cette these le dopage au bore du diamant (type p), et l'incorporation de phosphore et d'azote dans le diamant par implantation ionique. Nous avons elabore des couches minces de diamant par depot chimique en phase vapeur assiste par plasma micro-onde. Nous avons utilise dans notre etude diverses techniques de caracterisation : spectroscopie de diffusion raman, resonance paramagnetique electronique, resistivite en fonction de la temperature (de 100k a 1000k), effet hall, courants thermo-stimules, thermoluminescence. Les resultats obtenus montrent que le dopage au bore est aujourd'hui bien maitrise. Des mesures electriques sur une large gamme de concentration (de 5 10#1#6 a 8 10#2#0 b. Cm#-#3) montrent trois regimes de conduction differents : conduction par saut par plus proche voisin, conduction par la bande de valence, conduction metallique. Nous avons montre pour la premiere fois une saturation de la conductivite et une energie d'activation a haute temperature e#a/2 typique d'un taux de defauts compensateurs inferieur a 10%. Nous avons montre que l'implantation est la methode la plus efficace pour incorporer de l'azote en site substitutionnel dans le diamant. Neanmoins, l'incorporation d'azote semble induire indirectement des defauts paramagnetiques dans le diamant. Nous avons aussi montre que l'incorporation de phosphore en site substitutionnel est possible. Nous avons defini un seuil d'amorphisation compris entre 3 et 4 10#1#4 p. Cm#-#2. Toutefois, un nouveau defaut paramagnetique qui semble etre induit par le phosphore apparait apres recuit. La conduction est encore dominee par les defauts crees par l'implantation ionique. Ces resultats sont tres prometteurs pour des applications futures en microelectronique.
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Cai, Jingxuan. "Synthesis and applications of N-modified mesoporous carbons." Thesis, Lyon 1, 2015. http://www.theses.fr/2015LYO10011.
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Les carbones poreux ont été largement utilisés et étudiés ces dernières années. Ce travail de recherche porte sur la préparation de matériaux carbonés mésoporeux modifiés ou non par de l'azote. Tout d'abord, un carbone mésoporeux pur a été synthétisé. Puis des atomes d'azote ont été introduits dans ce carbone mésoporeux par deux méthodes de dopage ("in situ" et "post-synthèse" respectivement). La comparaison des propriétés acido-basiques dans des conditions différentes pour les trois types de matériaux mésoporeux carbonés, avec ou sans diazote, a été faite grâce à des techniques calorimétriques. Ces carbones mésoporeux ont aussi été utilisés dans l'adsorption de polluants, le stockage de l'hydrogène et en tant que supports pour les métaux précieux et l'oxyde de fer en catalyse. Les différentes performances dans ces applications ont été mises en relation avec les différentes propriétés structurelles et surfaciques causées par le dopage au diazotePorous carbon materials are widely used and studied in recent years. In this work, three kinds of mesoporous carbon materials were prepared. Firstly, cost-effective pure mesoporous carbon was synthesized. Then nitrogen atoms were introduced into the mesoporous carbon by “in situ” and “post” doping methods respectively. The comparisons of the acid-base properties in different conditions of the three kinds of mesoporous carbon materials with or without nitrogen were studied and revealed by different calorimetric techniques. The three kinds of mesoporous carbons were also applied in pollutants adsorption, hydrogen storage and as supports of precious metals and iron oxide in catalysis. The different performances in applications were related to the different structural and surface properties caused by the N-doping
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Waidmann, Stephan. "Elektronische Eigenschaften von Diamant und diamantartigen Kohlenstoffen." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2001. http://nbn-resolving.de/urn:nbn:de:swb:14-997953406187-81897.
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Im Hinblick auf das immense Potential von Diamant als Material für die Mikroelektronik wurden im Rahmen dieser Arbeit undotierte und dotierte Diamantfilme mittels chemischer Gasphasenabscheidung auf Silizium präpariert und anschließend auf ihre elektronischen Eigenschaften hin untersucht. Für Letzteres wurde hauptsächlich die Elektronen-Energieverlustspektroskopie in Transmission verwendet. In situ Gasphasendotierung oder Ionenimplantation wurde zur Dotierung der Filme mit Bor, Lithium oder Phosphor eingesetzt. Bei der Ionenimplantation wurde aufgrund der Erzeugung von Strahlenschäden generell eine Erhöhung des sp2-Anteils beobachtet: Letzterer konnte jedoch im Falle der Bordotierung durch eine, den Implantationsprozeß folgende, Hochtemperaturtemperung wieder deutlich vermindert werden. Für die in situ Dotierung mit Bor wurde eine Verringerung des sp2-Gehaltes mit steigender Dotierkonzentration gefunden. Für den Film mit der höchsten Borkonzentration konnte auch die B1s Absorptionskante untersucht werden. Sie gibt Hinweise auf den überwiegenden Einbau der Boratome in einer tetragonalen Orientierung. Das hiermit verbundene Vorhandensein von Akzeptoren führt zu elektronischen Anregungen im Energiebereich der Bandlücke, welche mittels Infrarotspektroskopie und EELS nachgewiesen werden konnten. Aus den EELS Messungen lassen sich Akzeptorkonzentrationen berechnen, welche wiederum den hohen Anteil an tetraedrisch eingebauten Boratomen bestätigen. Desweiteren untersucht wurden, als interessante Materialklasse mit weitreichendem technologischem Potential, undotierte und stickstoffdotierte, diamantartige amorphe Kohlenstoffilme und hierbei insbesondere die Abhängigkeit der elektronischen und optischen Eigenschaften von der Ionenenergie und dem Stickstoffpartialdruck während der Filmpräparation. Die Plasmonenergien, Massendichten, sp3-Anteile und die optischen Bandlücken der Filme wurden quantitativ bestimmt, wobei das jeweilige Maximum bei einer Ionenenergie von 100 eV gefunden wurde. Alle eben genannten Größen verringern sich kontinuierlich mit zunehmendem Stickstoffanteil. Eine Kramers-Kronig Analyse der Verlustspektren gibt Zugriff auf den Real- und Imaginärteil der dielektrischen Funktion und damit auf das Spektrum der Einteilchenanregungen. Die Hybridisierung der Kohlenstoff- und der Stickstoffatome wurde detailliert aus den jeweiligen 1s Absorptionskanten bestimmt. Weiterhin wurde Diamant als Modellsystem eines Festkörpers mit rein kovalenten Bindungen untersucht, insbesondere die Verlustfunktion von Diamant entlang mehrerer Hochsymmetriekristallrichtungen über einen großen Energie- und Impulsbereich. Aus den EELS Messungen erschließt sich unmittelbar die stark anisotrope Plasmonendispersion von Diamant. Aus dem Vergleich der experimentellen Spektren mit ab initio LDA Rechnungen, die sowohl Kristallokalfeldeffekte als auch Austausch- und Korrelationseffekte beinhalten, lassen sich direkt Rückschlüsse auf den Einfluß der verschiedenen Effekte ziehen. Schon im optischen Limit, aber umso mehr mit steigendem Impulsübertrag q, wird eine Überlagerung der kollektiven Plasmonanregung mit Einteilchenanregungen im Energiebereich des Plasmons beobachtet, woraus eine Kopplung zwischen beiden Arten von Anregungen resultiert. Abgesehen vom deutlichen Einfluß der Bandstruktur auf die Plasmonendispersion läßt die überaus inhomogene Elektronenverteilung von Diamant auf nicht zuvernachlässigende Kristallokalfeldeffekte schließen. Der Vergleich zwischen experimentellen und berechneten Spektren zeigt deutlich, wie die Kristallokalfeldeffekte in der Tat mit steigendem Impulsübertrag an Gewicht zunehmen und die Struktur der Verlustfunktion mitbestimmenIn the context of the immense potential of diamond as a material for use in the microelectronics industry, in this thesis pristine and doped diamond films have been deposited on silicon using chemical vapour deposition. Subsequently their electronic properties have been investigated using mainly electron energy-loss spectroscopy. Doping of the films with boron, lithium or phosphorous was carried out either via in-situ gas phase doping during film growth or using ion implantation. Upon ion implantation an increase of the carbon content with sp2 hybridisation has generally been found due to ion beam induced damage. In the case of boron doping it was possible to significantly reduce this sp2-contribution using a high temperature anneal. For the in-situ doping with boron, upon increasing doping concentration a decrease of the sp2-contribution was found. For the sample with the highest boron content the boron 1s absorption edge could also be investigated, providing evidence for the preferential incorporation of the boron atoms into tetrahedrally co-ordinated sites. This boron incorporation leads to the existence of electronic excitations in the energy range of the band gap, which could be observed using both infrared and electron energy-loss spectroscopy. From the electron energy-loss measurements it was possible to calculate acceptor concentrations which were consistent with the large amount of tetrahedrally co-ordinated boron atoms. A second theme in this thesis involved the study of pristine and nitrogen doped diamond-like amorphous carbon films, which are an interesting material class with far-reaching technological potential. Here the focus of the research concerned the dependency of the electronic and optical properties of the films upon the ion energy and the nitrogen partial pressure applied during the film preparation. The plasmon energies, mass densities, sp3 contribution and the optical band gaps of the samples were determined quantitatively, whereby the maximum in all these quantities was found to occur for ion energies of 100 eV. Furthermore, all of these characteristics were found to decrease continually with increasing nitrogen content. A Kramers-Kronig analysis of the loss spectra enabled the derivation of the real and imaginary parts of the dielectric function and with this of the complete spectrum of single particle excitations. The hybridization between the carbon and nitrogen atoms was also studied in detail from the analysis of the respective 1s absorption edges. Furthermore this thesis deals with the investigation of diamond as a model system for solids with pure covalent bonds. In particular, the loss function of diamond was measured along different high symmetry directions over a wide range of energy and momentum. Firstly, the EELS measurements showed directly the strongly anisotropic nature of the plasmon dispersion in diamond. Secondly, by the comparison of the experimental spectra with ab initio LDA-based calculations that include crystal local field effects as well as exchange and correlation contributions, conclusions can be drawn as to the influence of these quantities. In the optical limit, but even more so with increasing momentum transfer q, a superposition of the collective plasmon excitation and the single particle excitations in the energy range of the plasmon is observed. This energetic proximity results in a coupling between both types of excitations. Apart from the distinct influence of the bandstructure on the plasmon dispersion, the considerably inhomogeneous electron distribution of diamond would lead one to expect significant crystal local field effects in this system. The comparison between the experimental and the calculated spectra shows explicitly that the crystal local field effects increase with increasing momentum transfer and play an important role in defining the structure of the loss function
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Arnoult, Alexandre. "Dopage par modulation d'hétérostructures de semiconducteurs II-VI semimagnétiques en épitaxie par jets moléculaires." Université Joseph Fourier (Grenoble), 1998. http://www.theses.fr/1998GRE10237.
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Une etude theorique preliminaire a cette these a prevu que lorsque l'on introduit un gaz de trous bidimensionnel (2d) dans un puits quantique de semiconducteur semimagnetique, l'interaction entre les spins localises et les porteurs de charges induit une transition de phase ferromagnetique. Nous avons mis au point l'elaboration d'un tel systeme a base de tellurures en epitaxie par jets moleculaires, ainsi que la caracterisation au niveau microscopique des interfaces, du dopage et du transfert de porteurs dans le puits quantique. Ceci nous a permis d'elaborer des echantillons ayant donne lieu a toute une serie d'etudes physiques. Le dopage par modulation d'heterostructures de semiconducteurs ii-vi a base de tellure en epitaxie par jets moleculaires n'avait ete realise jusqu'a notre etude que pour un dopage de type n, sur des structures comportant du cdmgte comme materiau barriere, avec peu de magnesium. Or cet alliage est la clef de la realisation d'un bon confinement quantique dans les tellurures, surtout pour le dopage de type p ou la concentration en mg doit etre augmentee. L'utilisation d'une source d'azote ecr, dopant de type p, et l'optimisation des parametres de la croissance ont permis l'obtention d'un gaz de trous 2d de bonne densite, comme le montrent la spectroscopie optique, l'effet hall et la capacite-tension. L'etude de structures interdiffusees par sims, diffraction de rayon x et spectroscopie optique, nous a de plus permis de mieux comprendre les mecanismes de degradation en cours de croissance de nos couches comportant du magnesium, et dopees a l'azote. Un modele base sur la diffusion de l'azote a ete propose. Il a ensuite ete possible de realiser des structures semimagnetiques dans lesquelles l'interaction entre un gaz de trous 2d et des spins localises de manganese a permis la mise en evidence de la transition de phase ferromagnetique attendue theoriquement. Par ailleurs, un nouveau dopant de type n pour l'epitaxie par jets moleculaire des tellurures a ete teste avec succes sur des couches epaisses, ainsi que pour des heterostructures. Il s'agit de l'aluminium, dont le domaine d'utilisation est plus etendu que les autres dopants utilises jusqu'a present, puisqu'il permet d'obtenir une bonne efficacite meme sur des couches comportant du magnesium.
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Mu, Wei. "INVESTIGATION OF N SINGLE ATOM AND DIATOM DOPANT GAS EFFECT ON THE CONDUCTIVITY OF NITROGEN-DOPED ZNO THIN FILMS GROWN BY THERMAL EVAPORATION PROCESS." Miami University / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=miami1250195098.
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Haury, Axel. "Hétérostructures à puits quantique Cd(Mn)Te/CdMgZnTe dopées pgaz de trous et phase ferromagnétique." Université Joseph Fourier (Grenoble), 1997. http://www.theses.fr/1997GRE10205.
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Nous presentons la premiere mise en evidence d'une phase ferromagnetique dans des heterostructures a puits quantique semimagnetique cdmnte/cdmgznte dopees p par modulation (azote) dans les barrieres. Dans de tels echantillons, le transfert de trous des barrieres dans le puits cree un gaz de trous quasi-bidimensionnel dans la couche de cdmnte. Pour optimiser les conditions de dopage, une etude preliminaire a ete menee sur une serie d'echantillons a puits quantiques non magnetiques cdte/cdmgznte montrant que, dans des puits de 80 a, le gaz de trous devient metallique pour des densites superieures a 1. 5 x 10#1#1 cm#-#2. En outre, ces echantillons nous ont permis d'observer les deux types d'excitons charges x#+ et x#-. Dans les echantillons a puits semimagnetique cdmnte, l'interaction d'echange entre les ions magnetiques mn#+#+ et le gaz de trous en phase metallique ( 2 x 10#1#1 cm#-#2) cree un couplage ferromagnetique du type rkky entre les spins localises des ions mn#+#+. Dans des puits d'une largeur de 80 a et pour des concentrations de mn d'environ 3%, l'interaction ferromagnetique induite par le systeme de trous bidimensionnel devient superieure au couplage antiferromagnetique de superechange entre les ions magnetiques mn#+#+. Ceci se traduit par une transition de phase ferromagnetique a la temperature critique t#c d'environ 2 k. La phase paramagnetique au dessus de t#c est caracterisee par une augmentation spectaculaire de la susceptibilite magnetique.
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Even, Raymond. "Les premiers semiconducteurs moleculaires : les derives radicalaires des phtalocyanines." Paris 6, 1987. http://www.theses.fr/1987PA066161.
Full textAbstract:
Synthese de composes pc::(2)lu, pc::(2)ln(ln = yb,tm,dy,nd) a l'etat de grande purete et etude de leurs proprietes electriques intrinseques, ainsi que de celles de pcli, sur monocristaux et sur couches minces; mise en evidence de la possibilite de dopage de pc::(2)lu avec des composes organiques donneurs et accepteurs et avec pcli. Etude de l'absorption optique et observation de bandes de transfert de charge intramoleculaire, confirmee par ailleurs par rpe. Possibilite d'application de couches minces de pclu a la detection de gaz
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Rao, Jhan-Ying, and 饒展螢. "Effect of Nitrogen-, Boron- and Boron/Nitrogen-doping on Graphene for Energy Storage Application." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/z97k55.
Full textAbstract:
碩士國立臺灣科技大學
化學工程系
106
Graphene oxide sheets were synthesized from graphite flake by the modified Hummers method and it was doped by nitrogen, boron and both of them by mixing with nitrogen, boron and both of them, respectively and then used hydrothermal method at 180℃ for 12h. The DTA curve showed that the carbon decomposition temperature of nitrogen-, boron- and boron/nitrogen-doping graphene (NG, BG and BNG) are shifted to more high temperature comparing with rGO. Comparing the electrochemical data under three electrodes system, the Cyclic voltammetry (CV) capacitance of NG, BG, BNG and GO at 5 mV/s in 1M NaCl solution were 303, 262, 225 and 153 F/g, respectively. The specific capacitance of NG was higher than others. Therefore, (acid treated carbon nanohorns) acid-CNHox was synthesized and (N-doped carbon nanohorns) N-CNH was prepared by using same procedure with NG. The DTA curve displayed that the carbon decomposition temperature of acid-CNHox and N-CNH have same temperature. Comparing CV capacitance at 5 mV/s, acid-CNHox and N-CNH were 219 and 248 F/g, respectively. To further investigate NG and N-CNH, galvanostatic charge/discharge showed the specific capacitance of 128 and 95 F/g, respectively, at 0.8 A/g in 1M NaCl solution. The specific capacitance of NG and N-CNH were influenced by the surface area, nitrogen-containing and chemical structure (pyridinic-N, pyrrolic-N and quaternary-N moieties). Furthermore, after 5000 cycles, the capacitance retention of NG and N-CNH still retained 97.9% and 98.7% respectively.
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YohanYuwana and 蔡金榮. "Effects of Nitrogen Doping on the Capacitive Performance of Porous Carbons." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/41155447262457372624.
Full textAbstract:
碩士國立成功大學
化學工程學系
103
Effect of nitrogen doping on the capacitive performance of porous carbons were observed by ammonia doping during heat treatment at high temperature. The activated mesophase pitch and phenol formaldehyde carbons were mixed with carbon nanotube then were doped ammonia doping at 700 C for 30 min, 1 and 2 hours. The cell equipped with each nitrogen doping on porous carbons in 1 M Na2SO4 solution can reach a high capacitance value of 250 F g-1 at 0.05 A g-1 and retention 51 % at 100 A g-1. Nitrogen content on carbon surface can increase the polarity and hydrophobicity of carbon and facilitates the wettability between electrode and electrolyte. Wettability of inner-pore carbon surface, will make the electrolyte ions penetrate into inner pores easily and promote the utilization of charge storage. Moreover, because of nitrogen doping function as non-faradaic process or electrostatics as EDLC then N-Q and N-X which positively charges affect electron transfer through the carbon frameworks. As the result, the symmetric cells can deliver high energy of 22 kW kg-1 at low discharge rate with superior stability of 92% capacitance retention after 10,000 cycles of galvanostatic charge-discharge. Keywords: ammonia doping, activated porous carbons, nitrogen doping, EDLC, Na2SO4
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HUANG, HEI-YUAN, and 黃慧遠. "Effect of nitrogen doping on the photocatalytic properties of ZnO nanorods." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/e5n94k.
Full textAbstract:
碩士國立臺北科技大學
光電工程系
107
In this research, we used Metal-Organic Chemical Vapor deposition to grow ZnO nanorods. With Zn(C2H7O2)2 powder as the source, the Oxygen and Nitrogen were used to be the reaction gas and carrier gas. The ZnO nanorods were grown on Si (100) substrate. After the ZnO nanorods were grown, we annealed them in the Ammonia environment and nitrogen was doped with various concentrates into the nanorods in order to investigate the photocatalytic properties. The geometry of the nitrogen doped on nanorods were measured by scanning electron microscope (SEM). The electrical properties were measured by van der pauw and Hall effect measurement system. The crystallinity and crystal phase of the synthesized products were analyzed by X-ray diffraction and the optical properties were characterized by photoluminescence (PL) spectra. The photocatalytic activity of nitrogen doped ZnO nanorods were evaluated by measuring photocatalytic degradation of Methyl Orange in water under the illumination of UVA light. All the observed absorption spectra exhibit the maximum absorption at 465 nm by micro-spectrometer. Our results showed that the degradation rate increased as the carrier concentration of ZnO nanorods increased. When the ZnO nanorods were annealed in ammonia atmosphere of less than 100ml, the ZnO nanorods degradation rate increased as the concentration increased and band gap reduced. On the contrary, annealing under more than 100ml ammonia atmosphere reduced the concentration of the carrier, increased the energy gap, and further reduced the efficiency of degrading rate.
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"Enhancement of photocatalytic activity by doping nitrogen and boron into titanium dioxide." 2006. http://library.cuhk.edu.hk/record=b5892982.
Full textAbstract:
Leung Cheuk-wan.Thesis (M.Phil.)--Chinese University of Hong Kong, 2006.
Includes bibliographical references.
Abstracts in English and Chinese.
Abstract --- p.i
Abstract (Chinese) --- p.ii
Acknowledgement --- p.iii
Table of Contents --- p.v
Lists of Tables --- p.ix
Lists of Figures --- p.x
Chapter Chapter 1 --- Introduction --- p.1
Chapter 1.1 --- TiO2 Photocatalysis --- p.1
Chapter 1.1.1 --- Mechanisms of TiO2 Photocatalysis --- p.1
Chapter 1.2 --- Visible Light Photocatalyst --- p.4
Chapter 1.2.1 --- Preparation of Visible Light Ti02 Photocatalysts --- p.5
Chapter 1.2.1.1 --- Dye Sensitization --- p.5
Chapter 1.2.1.2 --- Metal Doping --- p.6
Chapter 1.2.1.3 --- Coupling of Semiconductors --- p.6
Chapter 1.2.1.4 --- Nonmetal Doping --- p.7
Chapter 1.3 --- Enhanced TiO2 Photocatalytic Activity under UV Light --- p.8
Chapter 1.3.1 --- Preparation of TiO2 Photocatalyst with Enhanced Activity in UV Light --- p.8
Chapter 1.3.1.1 --- Loading of Metal --- p.8
Chapter 1.3.1.2 --- Impurity Co-doping --- p.9
Chapter 1.3.1.3 --- Morphological Control --- p.10
Chapter 1.3.1.4 --- Increasing Surface Area --- p.10
Chapter 1.4 --- Summary --- p.11
Chapter 1.6 --- Aim of This Research and its Significance --- p.12
Chapter 1.7 --- References --- p.13
Chapter Chapter 2 --- Preparation of N-doped TiO2 with Enhanced Surface Area: A Detailed Characterization and Mechanism --- p.19
Chapter 2.1 --- Introduction --- p.19
Chapter 2.2 --- Experimental --- p.21
Chapter 2.2.1 --- Materials and Catalyst Preparation --- p.21
Chapter 2.2.2 --- Characterization --- p.21
Chapter 2.2.3 --- Photocatalytic Activity --- p.23
Chapter 2.3 --- Results and Discussion --- p.24
Chapter 2.3.1 --- XRD Analysis --- p.24
Chapter 2.3.2 --- UV-Vis Absorption Spectroscopy and Bandgap Energies --- p.27
Chapter 2.3.3 --- N2 Sorption Analysis --- p.29
Chapter 2.3.4 --- SEM Analysis --- p.33
Chapter 2.3.5 --- TEM Analysis --- p.35
Chapter 2.3.6 --- FT-IR Spectroscopy --- p.36
Chapter 2.3.7 --- Raman Spectroscopy --- p.39
Chapter 2.3.8 --- XPS Studies --- p.44
Chapter 2.3.9 --- PL Measurements --- p.49
Chapter 2.3.10 --- Photocatalytic Activity Measurements --- p.50
Chapter 2.3.11 --- Advantages of Using Urea as a N-doping Source --- p.54
Chapter 2.3.12 --- Mechanisms for N-doping --- p.56
Chapter 2.4 --- Conclusions --- p.58
Chapter 2.5 --- References --- p.59
Chapter Chapter 3 --- Preparation of Nanoporous Interstitial B-doped TiCO2 with Enhanced Photocatalytic Activity --- p.63
Chapter 3.1 --- Introduction --- p.63
Chapter 3.2 --- Experimental --- p.65
Chapter 3.2.1 --- Materials and Catalyst Preparation --- p.65
Chapter 3.2.2 --- Characterization --- p.66
Chapter 3.2.3 --- Photocatalytic Activity --- p.67
Chapter 3.3 --- Results and Discussion --- p.68
Chapter 3.3.1 --- XRD Analysis --- p.68
Chapter 3.3.2 --- UV-Vis Absorption Spectroscopy and Bandgap Energies --- p.71
Chapter 3.3.3 --- N2 Sorption Analysis --- p.73
Chapter 3.3.4 --- SEM and TEM --- p.76
Chapter 3.3.5 --- FT-IR Spectroscopy --- p.80
Chapter 3.3.6 --- Raman Spectroscopy --- p.82
Chapter 3.3.7 --- PL Measurements --- p.84
Chapter 3.3.8 --- XPS Studies --- p.85
Chapter 3.3.9 --- Photocatalytic Activity Measurements --- p.89
Chapter 3.3.10 --- State and Form of Boron in TiO2 Lattice and its Effects --- p.91
Chapter 3.4 --- Conclusions --- p.93
Chapter 3.5 --- References --- p.94
Chapter Chapter 4 --- Conclusions --- p.97
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Liou, Chang-Sin, and 劉長鑫. "Nonlinear band gap opening of graphene with boron and nitrogen co-doping." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/41553116726615115632.
Full textAbstract:
碩士淡江大學
物理學系碩士班
101
We report here a nonlinear band gap opening of graphene while varies the concentration of the co-doped B-N atoms. Measurements of X-ray absorption near edge structure (XANES) and X-ray emission spectra show an opening of band gap on graphene from 0 to 0.6 eV as the concentration of B-N dopant varying from 0 to 6%. Further increase on the doping level leads to a significant reduction on the band gap value. We demonstrate that such non-linear behavior is attributed to a change of the effect of B-N dopants on the electronic structure of grapheme. An locally redistributed π electronic state change by B-N dopant. The suggested physical picture is confirmed by the performed ab-initio calculation with considering the B-N structures obtained from experiments.
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He, Jhih-Syuan, and 何志軒. "Study of nitrogen-doping mesoporous activated carbon synthesized as supercapacitor electrode materials." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/15345492678302249579.
Full textAbstract:
碩士國立雲林科技大學
化學工程與材料工程系
104
In this study,ordered mesoporous carbons(OMC) synthesized by hard template method with sucrose and pyrrole as carbon source were fabricated as supercapacitor electrode.Various amounts of melamine were added to obtain different nitrogen content of nitrogen-doped OMC.The texture characteristics of the materials were determined by using nitrogen adsorption analysis. The morphology and surface functional groups were observed by X-ray photoelectron spectroscopy, transmission electron microscope and Fourier transform infrared spectroscopy.Electrochemical properties of the electrode materials were determined by using cyclic voltammetry (CV), galvanostatic charge/discharge measurement and electrochemical impedance. Experimental results show that nitrogen content will directly affect the specific capacitance of the ordered mesoporous carbon material. When 5-7 wt. % of nitrogen doped, the OMC material (0.1PM-OMC) has the highest specific capacitance. The specific capacitances of 355.1 F g-1 and 410 F g-1 were obtained at scan rate of 5 mV s-1 and current density of 0.5 A g-1, respectively.In addition, the carbon material provided a specific energy density of 71 W h kg-1 at a specific power density of 260 W kg-1, and maintained an energy density of 37 W kg-1 even at higher power density of 4783 W kg-1.
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Wiggins-Camacho, Jaclyn Dawn. "Effect of nitrogen doping on the electronic and catalytic properties of carbon nanotube electrode materials." Thesis, 2011. http://hdl.handle.net/2152/ETD-UT-2011-05-2669.
Full textAbstract:
This dissertation discusses the influence of nitrogen doping (N-doping) on the electronic and catalytic properties of carbon nanotubes (CNTs). These properties have been studied using a variety of techniques, in order to both qualitatively and quantitatively analyze the relationship between the nitrogen concentration and observed properties. Chapter 1 provides a general overview of CNTs and N-doping and details some of the previous research from our group. Chapter 2 discusses the assembly and characterization of free-standing electrode mats, which are used in order to understand the intrinsic physicochemical properties of the material without relying on the secondary influence of another conductive support. Raman microscopy, X-Ray photoelectron spectroscopy, scanning and scanning-tunneling electron microscopy, as well as electrochemical methods were all used to demonstrate the viability of the mat electrodes for further experiments. Chapter 3 addresses the examination of a range of nitrogen concentrations in order to better understand the effects of nitrogen concentration on the electrochemical and electrical properties such as the differential capacitance, density of states at the Fermi level (D(E[subscript F])), bulk conductivity and work function. These properties were studied using a variety of techniques, including UV-photoelectron spectroscopy, electrochemical impedance spectroscopy and conductive four point probe. Chapter 4 investigates the inherent catalysis of the nitrogen doped CNTs (N-CNTs) with respect to O2 reduction, and a complex mechanism is proposed. Electrochemical methods such as cyclic and linear sweep voltammetries as well as thermo-gravimetric analysis and gasometric analysis were all employed to determine heterogeneous decomposition rates as well as to detect intermediates of the O₂ reduction reaction. Chapter 5 discusses the electrocatalytic degradation of free cyanide (CN⁻) at the N-CNT mat electrodes. These results both provide further support for the mechanism discussed in Chapter 4, and present the opportunity for a potential application of N-CNTs for environmental purposes. Specifically, spectroscopic and electrochemical methods, in conjunction with theoretical models show both that the presence of CN⁻ does not inhibit O2 reduction, and that it can be effectively converted to cyanate (OCN⁻) at the N-CNT electrodes. Future work involving the assembly and characterization of transparent N-CNT films is discussed in Chapter 6.text
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Hsu, Cheng-Ju, and 徐正茹. "Doping of nitrogen and phosphorous into the graphite films by chemical solution method." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/b3qs35.
Full textAbstract:
碩士國立臺北科技大學
材料及資源工程系研究所
101
In the present study, we demonstrate the facile and green synthesis of nitrogen and phosphorus doped graphite films by using simple chemical solution method. We successfully doped nitrogen and phosphorus onto the graphite film by doping with ammonium hydroxide and phosphoric acid respectively. For a typical synthesis of composite, we used the silicon wafer as a substrate then it was oxidized to form silicon dioxide layer, and carbon thin film was deposited onto sample. Then it was immersed into the ammonium hydroxide and phosphoric acid solution followed by heated at 100℃ for various dwelling time. After the immersion the copper was deposited onto the obtained sample by using sputtering method; here copper is acting as a cap layer between the carbon layers for inhibiting the loss of doped material during the heat treatment process. Finally the product was annealed at 600℃, 700℃, 800℃ respectively, which leads to the formation of graphitic film. It should be noted that here we used copper as a control for the formation of graphite. The surface morphology of the composite was characterized by using optical microscope, which revealing that graphitic layers are formed as the combination of multiple graphene layers via Van der Waals interactions between individual graphite layers. Raman spectroscopy has been used to determine the properties of graphitic layers and the disorder of graphitic structure after graphitization. The synthesized composite films have been confirmed XRD. Further, the nitrogen and phosphorus doped graphite films have shown to improved sheet resistance and carrier concentration, implying the nitrogen and phosphorus leads to the enhanced and synergetic activity onto the graphitic film rather than intrinsic graphite. Finally, the versatile route of composite preparation could be a promising route for other composite materials preparation in near future.
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Yang, Wan-Ting, and 楊婉婷. "Fabrication and application of multi-layer graphene pn homojunction diode with nitrogen doping." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/92664k.
Full textAbstract:
碩士國立臺灣科技大學
光電工程研究所
105
Graphene is a two dimensional material with high surface area and high carrier mobility. Graphene is an attractive candidate for potential applications in optical and electrical devices due to these outstanding properties. Pristine graphene usually exhibits p-type behavior owing to the adsorption of oxygen and water vapor from the air. Therefore, modulating the grapheme electronic structure is an essential issue. Nitrogen doping is a facile approach used to tune the Fermi level above the Dirac point. Multi-layer graphene was synthesized in this study using chemical vapor deposition and then treated using nitrogen plasma. Under nitrogen plasma exposure the lateral graphene p-n junction was formed with the mask defining the doping regime. We investigated the device electrical characteristics using the half-wave rectifier. By modulating the nitrogen plasma power the current-voltage curve shows the Dirac point shifted from a positive value (+75 V) to a negative value (-55 V), indicating successful grapheme transformation into an n-type semiconductor. The nitrogen content increased from 1.4% to 2.8% with increased power. Pyrrolic-N content increased leading graphene FET to act as an n-type semiconductor. As shown from the Raman spectrum, the doping process induced defects. The graphene lateral homojunction exhibited diode properties. Good rectifier performance with very low distortion was identified by the oscilloscope. This device could be further applied in metal-oxide-semiconductor field-effect transistors and bipolar junction transistors.