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Cabanel, Régis. "Elaboration, caractérisation et propriétés électroniques de couches minces de nitrure de niobium et d'oxyde de niobium." Grenoble 2 : ANRT, 1986. http://catalogue.bnf.fr/ark:/12148/cb37596198b.
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Cabanel, Régis. "Elaboration, caractérisation et propriétés électroniques de couches minces de nitrure de niobium et d'oxyde de niobium." Grenoble INPG, 1986. http://www.theses.fr/1986INPG0051.
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Etude, entre 1 et 300 k, de la conductivite de couches minces granulaires. Mise en evidence d'une supraconductivite dans des films avec coefficient de temperature negatif. Mesures de reflexion optique dans le visible; la correlation avec les mesures de conductivite electrique
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Mbaye, Kouly. "Contribution à l'étude des propriétés en hautes fréquences de couches minces supraconductrices de nitrure de niobium." Paris 11, 1988. http://www.theses.fr/1988PA112061.
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Préparation. Caractérisation des échantillons en déterminant la composition par analyses Ager et émission photoélectronique RX. Détermination de la profondeur de pénétration des ondes ainsi que de la résistance de surface. On a pu classer NbN dans les supraconducteurs à couplage fort
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Linde, Alexander. "Preparation of cubic NbN via reactive diffusion and combustion synthesis in nitrogen gas." Montpellier 2, 2009. http://www.theses.fr/2009MON20149.
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Durant cette thèse, nous avons préparé par diffusion d'azote dans le niobium et par combustion auto-propagée sous atmosphère d'azote des poudres de nitrure de niobium de type δ-NbNx cubique avec des pourcentages atomiques x azote/niobium différents. Les paramètres de maille a de ces poudres ont été déterminés par diffraction des RX. Leurs températures de transition supraconductrice Tc ont été déterminées par des mesures de magnétisme. La détermination des valeurs exactes de x, a et Tc a permis de mettre en évidence un maximum pour le paramètre de maille et pour la température de transition pour une valeur de x = 0. 98 précisément. Une étude réalisée sur des particules de niobium de taille 100 µm a mis également en évidence la formation successive des phases α-Nb(N), β-Nb2N1±y, γ-Nb4N3±y, δ-NbN1±y ce qui est en total accord avec le diagramme de phases Nb-N référencé dans la littérature. Des expériences à basses pressions (P(N2) = 0. 12–10. 0 MPa) ont été réalisées pour étudier des modes différents de combustion par filtration avec “front concave” et “front plan”. Nous avons montré qu'un front concave se produisait dans un domaine de pression 0. 12−1. 0 MPa alors que dans le domaine 1−10 MPa, le front de combustion était plan, laissant donc présager d'une combustion stable. Dans les expériences à hautes pressions (P(N2) = 48−230 MPa) des conditions expérimentales bien spécifiques ont été choisies afin de limiter les pertes de chaleur. Pour les synthèses, les échantillons ont été entourés par une couche d'isolant de nitrure de bore poreux afin de réduire les pertes de chaleur pour obtenir ainsi une augmentation du coefficient “x” (jusqu'à 1. 015)This PhD thesis was aimed at obtaining of δ-NbNx powders with various nitrogen/niobium ratio x (both below and above the unity) via reactive diffusion and SHS in nitrogen gas. Lattice parameter a of cubic niobium nitride powders was determined by means of XRD. Their critical temperatures Tc were determined using magnetic measurements. Simultaneous high-accuracy measurements of the x, a and Tc values allowed us to unambiguously reveal the maxima in the a(x) and Tc(x) curves which was found to happen at x = 0. 98. The mechanism of phase formations in the diffusion product with a particle size of about 100 m was investigated. According to EPMA data, it was found to proceed in the following order: Nb → α-Nb(N) → β-Nb2N1±y → γ-Nb4N3±y → δ-NbN1±y that is in agreement with the recent phase diagram. SHS experiments at lower pressures (P(N2) = 0. 12–10. 0 MPa) were aimed at investigation of different combustion modes such as “surface” and “layer-by-layer” modes experimentally and theoretically. Combustion with a concave front (“surface” mode) was found to occur within the pressure range 0. 12–1. 0 MPa while that with a planar front (“layer-by-layer” mode), in the range 1–10 MPa. SHS experiments at high pressures (P(N2) = 48–230 MPa) were mostly oriented on the investigation of influence of different heat conditions. It was shown that upon filtration combustion infiltration of nitrogen gas into the sample body is not the only parameter which limits the extent of nitriding of Nb powder. Gas permeable heat insulation is recommended in order to decrease heat loss from the sample into environment and thus to provide more favorable conditions for the achievement of higher extent of nitriding. Using heat insulation high extent of conversion (x = 1. 015) was obtained at lower pressures than in previous studies
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Mbaye, Kouly. "Contribution à l'étude des propriétés en hautes fréquences de couches minces supraconductrices de nitrure de niobium." Grenoble 2 : ANRT, 1988. http://catalogue.bnf.fr/ark:/12148/cb376161845.
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Jacquemin, Manoël. "Structure et propriétés supraconductrices de films de nitrure de niobium épitaxiés par CVD à haute température." Thesis, Université Grenoble Alpes (ComUE), 2019. http://www.theses.fr/2019GREAI054/document.
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Les études concernent le développement de dispositifs supraconducteurs de détection de photon unique. Le nitrure niobium (NbN) est un matériau adapté à l’élaboration de fils supraconducteurs de la cible du détecteur. Ces travaux ouvrent des perspectives sur l’élaboration de films de nitrure de niobium épitaxié sur saphir par la méthode de dépôt chimique en phase vapeur (CVD). L’élaboration des films minces (5-100 nm) est effectuée à haute température (1000°C à 1300°C) à partir de chlorure de niobium et d'ammoniaque dilués dans l'hydrogène (H2-NH3-NbCl5). Les substrats sont du saphir monocristallin (Al2O3) orienté (0002), du nitrure d'aluminium (AlN) orienté (0002) et de 'oxyde de magnésium (MgO) orienté (100).L'étude des relations d’épitaxie au cours de la croissance du nitrure de niobium sur le substrat de saphir a tout d'abord été effectuée. L’observation des microstructures et des orientations cristallines des différents films élaborés a permis de mettre en évidence les relations existant entre l'état de surface du substrat et le mode de croissance du NbN. Les perspectives d'utilisation de substrats monocristallins de type MgO et AlN sont présentées en conclusion.L’étude du procédé de croissance et les relations existant entre les conditions d'élaboration et la "qualité" des films minces a permis de dégager les fenêtres expérimentales conduisant à une croissance épitaxiale. L’énergie d’activation des réactions de croissance et les conditions de sursaturation propices à la croissance épitaxiale ont été calculées.L'étude des relations entre les propriétés structurales et les caractéristiques supraconductrices des films a permis de relier la température de transition supraconductrice à la densité de défauts atomiques, aux défauts microstructuraux, à l’épaisseur des films élaborés et à leur état de contrainte. Il existe une relation linéaire entre l’espace interréticulaire des plans parallèles au substrat et la température de transition supraconductrice.Enfin, l'étude de la durabilité des films ultraminces (5 – 8 nm) de nitrure de niobium a été menée. Dans cette étude les propriétés électriques et supraconductrices de films élaborés à 1000°C et 1200°C sur des substrats de saphir et de couches épitaxiales d'AlN ont été analysées sur une durée de six mois. Les propriétés des films évoluent surtout au cours du premier mois. Le dépôt effectué à haute température permet de limiter la dégradation rapide des films et de conserver leurs propriétés supraconductricesThe studies concern the development of superconducting devices for single photon detection. Niobium nitride (NbN) is a material suitable for the production of superconducting wires for the detector target. This work is opening up perspectives on the development of epitaxial niobium nitride films on sapphire by the chemical vapor deposition (CVD) method. The production of thin films (5-100 nm) is carried out at high temperature (1000°C to 1300°C) from niobium chloride and ammonia diluted in hydrogen (H2-NH3-NbCl5). The substrate is oriented single crystalline sapphire (Al2O3) (0002), aluminum nitride (AlN) (0002) or magnesium oxide (MgO) (100).The study of epitaxial relationships during the growth of niobium nitride on the sapphire substrate was first performed. Observation of the microstructures and crystalline orientations of the various films processed made it possible to highlight the relationships between the surface state of the substrate and the growth mode of NbN. The potential for using single crystal substrates such as MgO and AlN is discussed in the conclusion.The study of the growth process and the relationships between the working conditions and the "quality" of thin films made it possible to identify the experimental windows leading to epitaxial growth. The activation energy of the growth reactions and the supersaturation conditions favorable to epitaxial growth were calculated.The study of the interactions between the structural properties and superconducting properties of films has allowed the superconducting transition temperature to be linked to the density of atomic defects, microstructural defects, the thickness of the films and their stress state. There is a linear relationship between the interplanar space of planes parallel to the substrate and the superconducting transition temperature.Finally, the durability of ultra-thin films (5 - 8 nm) of niobium nitride was studied. The electrical and superconducting properties of films processed at 1000°C and 1200°C on sapphire substrates and epitaxial layers of AlN were analyzed over a period of six months. The properties of films change most notably during the first month. High temperature deposition limits the rapid degradation of the films and preserves their superconducting properties
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Goupy, Johannes. "Optimisation de détecteurs pour l'astronomie du rayonnement X : développement de jonctions supraconductrices pour l'isolation thermique dans les interconnexions." Phd thesis, Université de Grenoble, 2012. http://tel.archives-ouvertes.fr/tel-00877895.
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L'avenir des nouvelles caméras embarquées pour l'astrophysique spatiale semble passer par unaccroissement du nombre de pixels et un fonctionnement à très basse température (en dessous de 0,1 K).Avec cette évolution, le nombre important de fils en sortie du détecteur refroidi représente souvent lacharge thermique prédominante sur la source froide (cryostat).Dans ce contexte, l'isolation thermique entre les différents circuits de détection est un point crucial pources caméras. Une brique technologique innovante a été développée pour apporter une solution présentantune excellente conduction électrique couplée à une grande isolation thermique. Cette innovation,protégée par un brevet, permet de résoudre cet apparent paradoxe. La solution proposée consiste enl'empilement d'un grand nombre de couches minces de matériaux supraconducteurs dans lesinterconnexions.La résistance thermique à chaque interface est dépendante des propriétés élastiques des matériaux,de la qualité des interfaces et de la température à laquelle le système fonctionne. A très basse température,le modèle AMM, couplé aux mesures des caractéristiques des matériaux composants la multicouche,permettent une estimation théorique de la résistance thermique pour une interface. Les mesures effectuéesavec les liaisons supraconductrices à forte résistivité thermique concordent avec les estimationsthéoriques. Nous avons ainsi pu mesurer des résistances thermiques de l'ordre de 3,3.105 K/W à 200 mKpour une multicouche composée d'une succession (62 interfaces) de couches minces de nitrure de titaneet de niobium sur une surface de 16 mm2. Dans les conditions d'utilisation prévues pour une camérarayons X de 4000 pixels microcalorimétriques, l'utilisation de cette brique technologique devrait assurerune charge thermique sur la source froide (à 50 mK) très inférieure au μW pour plus de 8000 pointsde contact. Ce dispositif pourra être utilisé à l'avenir dans nombre de projets cryogéniques, lorsqu'une excellenteisolation thermique associée à une excellente conduction électrique sera recherchée.
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Setzu, Romano. "Etude et réalisation de jonctions Josephson en nitrure de niobium à barrière semi-métallique en TaxN ; application aux circuits logiques micro-ondes à impulsions quantiques RSFQ." Phd thesis, Université Joseph Fourier (Grenoble), 2007. http://tel.archives-ouvertes.fr/tel-00194521.
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Cette thèse a permis le développement et l'optimisation de jonctions Josephson SNS (Supraconducteur–métal Normal–Supraconducteur) à électrodes NbN et barrière TaxN de haute résistivité. On a montré une bonne reproductibilité des propriétés des couches TaxN en fonction des paramètres du dépôt. Les tricouches NbN/TaxN/NbN présentent la température critique élevée attendue (16K). Les jonctions présentent une dépendance claire du produit RnIc (courant Josephson x résistance normale, indicateur de la fréquence Josephson maximale) en fonction de la pression d'azote dans le dépôt. On a ainsi obtenu sur des collections de jonctions des produits RnIc très élevés, jusqu'à 3,74mV à 4,2K pour des densités de courant critique Jc voisines de 15kA/cm2. Les jonctions présentent les comportements Josephson attendus, (diffraction de Fraunhofer et marches de Shapiro) jusqu'à 14K. La dépendance du Jc des jonctions en fonction de la température a été interpolée en utilisant le modèle des jonctions SNS longues dans la limite sale, donnant une longueur de cohérence du métal normal autour de 3,8nm à 4,2K. Nous avons enfin étudié un procédé de fabrication multiniveaux adapté aux circuits RSFQ (Rapid Single Flux Quantum), comprenant un plan de masse commun et des résistances de polarisation. Pour conclure, nous avons montré la supériorité de performances des jonctions NbN/TaxN/NbN sur les jonctions actuelles en niobium et leur intérêt pour réaliser des circuits numériques RSFQ compacts. En effet ces jonctions s'affranchissent des résistances d'amortissement des jonctions Nb, et peuvent fonctionner jusqu'à des fréquences d'horloge supérieures à 150 GHz et jusqu'à 10K (contre 50 GHz en Nb à 4,2K).
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Larrey, Vincent. "Etude et realisation de jonctions sis a base de nitrure de niobium et d'une barriere tunnel adaptee permettant la montee aux frequences thz des instruments heterodynes." Paris 6, 1998. http://www.theses.fr/1998PA066542.
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Pour preparer les futures missions sur satellites en radioastronomie, les melangeurs utilisant des jonctions josephson supraconducteur / isolant / supraconducteur (sis) de type nbn/mgo/nbn ou nbn/a1n/nbn presentent un grand interet dans l'optique de la montee en frequence des instruments heterodynes. Ce memoire presente l'etude, la fabrication et la qualification de dispositifs a base de jonctions sis en nitrure de niobium. Ce travail comprend une partie de caracterisation electrique et structurale de films minces nbn obtenus par pulverisation cathodique reactive et qui aboutit a la determination de conditions optimales de depot. La fabrication de jonctions josephson nbn/mgo/nbn de petite surface (1 m 2) et de fortes densites de courant (>10 ka. Cm 2) est ensuite etudiee de facon a obtenir une technologie fiable et une bonne reproductibilite des parametres geometriques et electriques. Associe a la caracterisation i(v), un procede de traitement thermique permet le controle des densites de courant critique et l'amelioration de la qualite des dispositifs. La premiere qualification a 300 ghz de notre technologie donne une temperature de bruit de recepteur de 726 k ; mais au dela de ce resultat, la qualite des caracteristiques electriques de nos films nbn et des courbes i(v) statiques sont prometteuses pour des applications a des frequences proches du thz.
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Baubert, Jean Benoît Martin. "Superconducting hot electron bolometers on thin membranes for SHAHIRA." Paris 6, 2005. http://www.theses.fr/2005PA066617.
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Daulle, Armelle. "Conception, réalisation et caractérisation de capteurs de puissance micro-onde." Université Joseph Fourier (Grenoble), 1999. http://www.theses.fr/1999GRE10167.
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Le travail presente dans ce memoire se compose de deux etudes realisees conjointement et de facon complementaire. La premiere concerne la conception et la caracterisation de deux capteurs de puissance micro-onde dont le fonctionnement est base sur la conversion de l'energie haute frequence en chaleur. L'un, destine a des mesures rapides de signaux de telecommunications, met a profit la grande sensibilite thermometrique des couches minces de nitrure de niobium. La mesure de la puissance se fait selon un principe de compensation. Un temps de reponse de 2 s, tres competitif vis a vis des capteurs a diodes, a ete obtenu dans la gamme de puissance + 10 dbm ; +28 dbm et a des frequences de l'ordre du gigahertz. L'autre, destine a des mesures de puissances moyennes, utilise un element sensible realise en couche mince metallique taperisee. Son principe de fonctionnement n'a, a notre connaissance, jamais ete experimente pour la mesure de puissance micro-onde dans les structures planaires. Ces capteurs ont pour point commun le couplage electromagnetique/thermique, qui peut generer non-linearites, points chauds, regimes transitoires rapides et derives thermiques lentes. Dans le but de detecter ces phenomenes simultanes mais d'echelles tres differentes, nous avons developpe un outil de modelisation numerique par ondelettes, utilisant la methode de galerkin en deux dimensions. La seconde partie de ce memoire est consacree a la description des differentes versions de notre algorithme et de sa mise en uvre numerique. Developpe, teste et mis au point sur un cas fictif d'electromagnetisme, le programme a ensuite ete adapte a la resolution de deux problemes thermiques relatifs a nos capteurs.
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Lyne, Michael Peter. "High resolution spectroscopy of aminoborane and niobium nitride." Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/26442.
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The infrared spectrum of aminoborane (NH₂BH₂) was recorded by a Fourier transform interferometer and the 1550-1750 cm⁻¹ region of the spectrum was rotationally analyzed by a new search/match algorithm based on ground state combination differences. Sub-bands from four separate vibrational bands were discovered in this region. The interaction scheme was deduced to be a three-way anharmonic resonance between the V₃, V₇ + VB, and 2v₆ levels with the fourth level, V₆ + V₁₂ induced by a Coriolis mechanism with the members of the triad. The first order anharmonic constants were approximated by a least squares fit of the triad intensities: W₃₇₈ = 8.4±0.1 cm⁻¹, W₃₆₆ = 15.8±0.4 cm⁻¹ with W₇₈₆₆ held fixed at zero. Perturbations from unseen interloper levels plus the fully correlated nature of the pure vibrational anharmonic interaction prevented a successful fit of the rotational structure of this system. Both the search/match and the intensity least squares algorithms were developed for this work.
Four sub-bands in the red-orange region of the laser induced fluorescence spectrum of niobium nitride (NbN) were rotationally analyzed. Analysis of three sub-bands of the ³ϕ₂ - ³Δ₁ system allowed the vibrational spacings of each electronic state to be determined: ΔG½ = 986.351 cm⁻¹, ΔG1½ = 977.855 cm⁻¹ for the ³ϕ₂ state and ΔG1½, =. 1033.739cm⁻¹ for the ³Δ₁, state. The previously unassigned ³Π₁-³Δ₂ (0-0) sub-band was discovered 970 cm⁻¹ below its expected position of 18025 cm⁻¹. The electronic state assignment of this transition was confirmed by -wavelength resolved fluorescence measurements made with a diode array detector mounted on a spectrometer. A description of how the diode array detector was interfaced into the experiment is given.Science, Faculty of
Chemistry, Department of
Graduate
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Huang, Gejian. "High resolution spectroscopy of niobium nitride and vanadium oxide." Thesis, University of British Columbia, 1988. http://hdl.handle.net/2429/27961.
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This thesis reports the spectroscopic studies of two gaseous molecules, niobium nitride (NbN) and vanadium oxide (VO). The ³∏ — ³∆ electronic transition of NbN was recorded by laser-induced fluorescence at Doppler-limited resolution as well as at sub-Doppler resolution. Two almost identical branch features are observed in the ³∏₀ — ³∆₁ sub-band because the A-doubling in the ³∏₀ sub-state is large and almost J-independent. The ³∏₁ — ³∆₂ transition is shifted 600 cm⁻¹ to the red of its central first-order position as a result of very large second-order spin-orbit interaction effects. The shift is believed to be caused principally by the coupling of the ³∏₁ component with the ¹∏ state from the same electron configuration, with a smaller contribution from coupling of the ³∆₂ component
of the ground state with the low-lying ¹∆ state. The ³∏ and ¹∏ states are unusual in that their zero-order energies are calculated to be within 100 cm⁻¹, based on the newly observed ¹∏₁ - ³∆₂ (1,0) transition; this means that they form a very fine example of a "super-multiplet", where the spin-orbit effects within and between the states of a particular
electron configuration are larger than their separations. The spin-orbit interactions are so extensive that the fine structure can only be fitted using effective rotational and hyperfine Hamiltonians for the individual sub-states, as in case (c) coupling. From the determined hyperfine constants h and C⍳ for the three ³∏(v — 0) components, the Fermi contact constant b was found to be negative, which is consistent with the configuration πδ. Rotational analysis gave the ³∏ and ³∆ bond lengths as 1.6705 Å and 1.6622 Å, respectively.
The near-infrared electronic system of VO has been recorded in emission at Doppler-limited resolution with the 1-m FT spectrometer at Kitt Peak National Observatory. The spectrum in the 4000-14000 cm⁻¹ region consists of numerous transitions with most of them extensively analyzed. Two isolated sub-bands at 7200 cm⁻¹ have been assigned as the two spin components of a ²∏ — ²∆ transition and rotationally analyzed. The rotational constant for the lower state is found to be larger than that for the σδ² X ⁴∑⁻ ground state, indicating that the ²∆ state arises from the electron configuration σ²δ. The configuration assignment was confirmed by the derived spin-orbit coupling constant for the ²∆ state. Similar reasoning applied to the ²∏ upper state suggests that it may arise from the configuration σ²π, though the preliminary study of the hyperfine structure argues against this assignment.Science, Faculty of
Chemistry, Department of
Graduate
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Schwartz, Viviane. "Preparation and Reactivity of Niobium-Containing Hydrotreating Catalysts." Diss., Virginia Tech, 2000. http://hdl.handle.net/10919/26368.
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A series of niobium-containing nitride and carbides were prepared by a temperature-programmed synthesis method. The catalysts synthesized comprised a monometallic niobium oxynitride and a new bimetallic oxycarbide supported system, Nb-Mo-O-C/Al₂O₃ (Mo/Nb = 1.2; 1.6; 2.0).
In the case of the niobium oxynitride, the progress of formation was analyzed by interrupting the synthesis at various stages. The effect of the heating rate on product properties was also investigated. The solid intermediates and the final niobium oxynitride were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), elemental analysis (CHNS), and gas adsorption techniques. The solid state transformation occurred directly from Nb₂O₅ to NbNxOy without any suboxide intermediates.
The bimetallic supported oxycarbide materials were also characterized by X-ray diffraction (XRD), gas adsorption techniques, X-ray photoelectron spectroscopy (XPS), and near-edge X-ray absorption fine structure (NEXAFS). It was found that the electronic properties of the oxycarbide were modified by the interaction with the Al₂O₃ support, and that most of the oxygen atoms were associated with the niobium rather than the molybdenum atom. All of the niobium-containing catalysts were tested in a three-phase trickle-bed reactor for the simultaneous hydrodenitrogenation (HDN) of quinoline and hydrodesulfurization (HDS) of dibenzothiophene. The niobium oxynitride presented low HDS activity and moderate HDN activity, whereas the supported bimetallic oxycarbide was found to be highly active for both, HDN and HDS, demonstrating higher activities than the commercial sulfided Ni-Mo/Al₂O₃ when compared on the basis of active sites.
In addition to these studies a comprehensive investigation of the HDN reaction mechanism was carried out over bulk unsupported Mo₂C, NbC, NbMo₂-O-C, and compared with the mechanism over a sulfide catalyst, MoS₂/SiO₂. For this purpose, a comparison of the HDN rate of a series of isomeric amines was performed, and the reaction occurred mainly through a β-elimination mechanism for all catalysts. Temperature programmed desorption of ethylamine was used to investigate the acid properties of the catalytic surfaces, and a good agreement between the specific rate of reaction and the number of Brønsted acid-sites was obtained. Infrared spectroscopy showed that the amines interacted with acidic centers to form adsorbed quartenary ammonium species. The deamination reaction over the carbide and sulfide catalysts probably occurs by a concerted push-pull mechanism involving basic sulfur species and Brønsted-acidic centers. In order to obtain more insight into the mechanism a study of the pyridine HDN network was carried out.All of the catalysts showed the same activity trend: the reactivity of n-pentylamine was high, while those of piperidine and pyridine were relatively low. The carbide catalysts showed higher selectivity towards HDN products than the sulfide catalyst at the same conversion levels. The higher selectivity was related to the higher ratio (r = k₂/k₁) between the rate constants of the two consecutive reactions, hydrogenation of pyridine (k₁) and ring opening of piperidine (k₂). The order of activity of the carbides and sulfide differed considerably depending on the substrate. However, for the pyridine reaction network the similarity in product distribution suggested that a similar surface composition, a carbosulfide, was attained during the reaction.Ph. D.
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Dane, Andrew E. (Andrew Edward). "Reactive DC magnetron sputtering of ultrathin superconducting niobium nitride films." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/97257.
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Thesis: S.M. in Electrical Engineering, Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2015.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references.
DC reactive magnetron sputtering was used to deposit few-nanometer-thick films of niobium nitride for fabrication of superconducting devices. Over 1000 samples were deposited on a variety of substrates, under various chamber conditions. Sheet resistance, thickness and superconducting critical temperature were measured for a large number of samples. Film Tc was improved by changing the way the samples were heated during the deposition, by ex situ rapid thermal processing, and in some cases by the addition of an RF bias to the substrate holder during the sputter deposition. These improvements to the deposition of NbN have enabled the production of superconducting nanowire single photon detectors whose quantum efficiency saturates and was the starting point for work on the superconductor-insulator transition.
by Andrew E. Dane.
S.M. in Electrical Engineering
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Baunemann, Arne. "Precursor chemistry of tantalum and niobium nitride for MOCVD and ALD applications." [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=982633009.
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Archer, Lucy Elizabeth. "Optical properties of ultra-thin niobium nitride films for single photon detectors." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/112044.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Physics, 2017.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 75-78).
In this thesis I made a study of the properties of reactively sputtered ultra-thin films of niobium nitride (NbN) and niobium titanium nitride (NbTiN). Using Variable Angle Spectral Ellipsometry (VASE), I found that the optical properties of NbN films appear to have a critical thickness above which the optical parameters stabilize. I also found that the deposition process has better stability over time for thicker films than for thinner ones; that is, when films are deposited weeks apart, the thinner films show more variation in thickness and optical properties than do the thicker films. The data also suggest that the crystallinity of the substrate upon which the NbN is deposited has a significant effect on the optical parameters. The set of films deposited for the optical study was also tested against a universal scaling law for thin film superconductors, which seems to support the existence of the critical thickness, below which the properties change significantly and do not conform to the power law scaling that holds for thicker films. Finally, I explored recipes for depositing NbTiN with our sputtering system, in the hope of creating films that have better properties than NbN to be used in device manufacturing. I was able to create films with the same properties as our current NbN films with minimal optimization, and further work in this area should result in NbTiN films that are better than our NbN films.
by Lucy Elizabeth Archer.
S.M.
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Lichtenwalner, Daniel Jenner. "The ion-beam reactive sputtering process for deposition of niobium nitride thin films." Thesis, Massachusetts Institute of Technology, 1990. http://hdl.handle.net/1721.1/42466.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1990.Vita.
Includes bibliographical references (leaves 284-290).
by Daniel Jenner Lichtenwalner.
Ph.D.
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Acevedo, Reyes Daniel Epicier Thierry Perez Michel. "Evolution de l'état de précipitation au cours de l'austénitisation d'aciers microalliés au vanadium et au niobium." Villeurbanne : Doc'INSA, 2007. http://docinsa.insa-lyon.fr/these/pont.php?id=acevedo_reyes.
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Acevedo, Reyes Daniel. "Evolution de l'état de précipitation au cours de l'austénitisation d'aciers microalliés au vanadium et au niobium." Lyon, INSA, 2007. http://theses.insa-lyon.fr/publication/2007ISAL0008/these.pdf.
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Les carbonitrures de vanadium et de niobium permettent de contrôler la taille de grain lors des traitements en phase austénitique. Une optimisation du traitement thermique nécessite de connaître l’évolution de l’état de précipitation, mais peu de données sont disponibles à présent sur le sujet. Cette étude porte sur le suivi des cinétiques de réversion des carbures de vanadium et de niobium dans l’austénite, sur deux alliages modèles de haute pureté FeCV et FeCVNb, et sur une nuance industrielle destinée à la fabrication d’aciers à ressorts. L’étude expérimentale combine plusieurs techniques expérimentales : la structure et la composition chimique des précipités sont déterminées par microscopie électronique en transmission et techniques associées (analyse EDX, imagerie HAADF), la distribution de taille des particules est mesurée par microscopie électronique à balayage (grâce à un détecteur d'électrons transmis), et la fraction volumique des précipités est suivie par dosage chimique des éléments précipités. Dans le but de prédire l’évolution de l’état de précipitation au cours du traitement d’austénitisation, un modèle de précipitation-réversion est développé. Ce modèle permet de décrire (i) l’existence d’un précipité binaire en prenant en compte l’écart à la stœchiométrie, (ii) la coexistence de deux précipités binaires indépendants, (iii) l’évolution d’une seule famille de précipités ternaires mixtes à composition chimique variable (VxNb1-xC). Ces différentes approches ont été validées sur les alliages modèles, puis appliquées aux cas de la nuance industrielleGrain size control during heat treatments in austenite can be ensured by vanadium and niobium carbonitrides. However, the evolution of the precipitation state must be known to optimise the austenisation treatment, and no quantitative characterisation of this kind is available nowadays. This study deals with the dissolution kinetics of vanadium and niobium carbonitrides in austenite, for two high purity model alloys FeCV and FeCVNb, and a commercial alloy designed for springs fabrication. The characterisation combines several experimental techniques : structure and chemical composition of precipitates are established by transmission electronic microscopy and related techniques (EDS analysis, HAADF), particle size distribution is measured by means of scanning electronic microscopy (using a STEM detector), and volume fraction of precipitates is estimated by dosing the precipitated phases after an electrolytic dissolution of the matrix. In order to predict the evolution of the precipitation state during an austenitisation treatment, a precipitation-dissolution model has been developed. The modelling approach used in this work allows the description of (i) a non stoichiometric binary precipitate, the coexistence of two independent binary precipitates, (iii) the evolution of a single family of homogeneous ternary precipitates with varying chemical composition (VxNb1-xC). These different approaches were calibrated and validated on model alloys, then applied to the industrial alloy
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Decams, Jean-Manuel. "Synthese et caracterisation de derives du niobium et du tantale avec des ligands azotes bidentes fonctionnalises : precurseurs potentiels de nitrures par cvd." Nice, 1999. http://www.theses.fr/1999NICE5376.
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Les procedes de chimie douce (mocvd, aacvd) exigent des precurseurs solubles et/ou volatils. Seuls des amidures homo et heteroleptiques de tantale et de niobium ont permis d'obtenir des films de tan et nbn par mocvd. Ils sont tous sensibles a l'hydrolyse et necessitent l'emploi de gaz vecteurs reactifs. L'utilisation de ligands rigides multidentes mono ou dianioniques capables de stabiliser des centres metalliques electrophiles nous a semble representer une alternative. Les benzamidinates et guanidinates (me 3si) 2nc(ncy) 2 2nbcl 2, p-tolylc(nsime 3) 2 2nbcl 2, p-tolylc(nsime 3) 2 2tacl 3, p-tolylc(nsime 3) 2 2tacl 2(net 2) 2 et (me 3si) 2nc(ncy) 2tacl 2(et 2n) 2 ont ete synthetises, caracterises et etudies par modelisation moleculaire. Nous avons montre que le mode de coordination, la structure ainsi que la stabilite thermique de ces ligands sont fonctions des interactions steriques des differents groupes portes par les atomes du cycle chelate. Tous ces complexes sont stables en solution et permettent d'atteindre des solutions sources suffisamment concentrees pour une utilisation dans des reacteurs a source liquide d'injection. Des reactions de metathese entre des phenylenediamidures ou naphtalenediamidures de lithium et differents halogenures de tantale et de niobium ont conduit a 4,5-me 2-o-c 6h 2(nsime 3) 2 2mcl avec m = ta, nb et 1,8-c 1 0h 6(nsime 3) 2tacl(net 2) 2. Ces complexes sont extremement solubles et stables dans tous les solvants organiques usuels. Le ligand 4,5-me 2-o-c 6h 2n(sime 3) 2 2 a permis d'obtenir 4,5-me 2-o-c 6h 2(nsi 2me 4 , 5cl 1 , 5)ntacl 3(dme) selon un mecanisme reactionnel original aboutissant a la formation de liaison si-cl (ligand) ainsi qu'un mode de coordination inhabituel du ligand. La plupart de ces complexes presentent egalement des proprietes physico-chimiques et structurales permettant d'envisager des applications dans divers systemes catalytiques comme la polymerisation d'olefines.
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Modarres, Tehrani Zoreh. "Etude électrochimique de la réactivité de complexes biscyclopentadiéniques du niobium vis à vis de fonctions organiques azotées (nitrile, hydroxylamine, amine, azo, nitroso et azoxy)." Dijon, 1997. http://www.theses.fr/1997DIJOS023.
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Ce mémoire est consacré à l'électrosynthèse, à la reactivite et à l'étude du comportement électrochimique de complexes organométalliques du niobium. La première partie de ce mémoire décrit le processus d'isomérisation du ligand nitrile pour des complexes du niobocène en fonction du degré d'oxydation du centre métallique. La seconde partie indique une nouvelle voie de synthèse de complexe imido du niobocène par action d'hydroxylamine aromatique sur le monochlorure de niobocène. La réduction monoélectronique de ces dérivés conduit à des complexes dimériques du niobium (IV) diamagnétiques. En présence de dioxyde de carbone ceux-ci évoluent vers la formation de dérivés carbonato du niobocène. La protonation du complexe imido conduit au complexe cationique amido dont la réduction électrochimique s'avère être catalytique. L'action d'amines aliphatiques sur les dihalogénures de niobocène conduit dans certaines conditions opératoires au complexe imido correspondant. La troisième partie de ce mémoire décrit l'étude de la réduction de dichlorure de niobocène vis à vis du groupe diazo (azobenzène et benzo(c)cinnoline). Si dans le premier cas on accède à des complexes du niobocène contenant le ligand azobenzène, en présence de benzo(c)cinnoline, on assiste à une élimination des deux ligands cyclopentadiényles avec formation d'un cluster a trois atomes de niobium. La dernière partie de ce travail traite de la réactivité de dichlorure de niobocène en présence de nitrobenzène et d'azoxybenzène. Dans le premier cas on démontre une propriété radicalaire non usuelle du complexe du niobium dont la réaction induit une modification du mode de coordination d'un des ligands cyclopentadiényles. Dans le deuxième cas le monochlorure de niobocène s'avère etre un agent de désoxygénation particulièrement efficace pour la transformation d'azoxybenzène en azobenzène.
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Carvalho, Renata Gomes. "Deposição e caracterização de filmes finos de NbAIN por magnetron sputtering reativo." Universidade Federal de Sergipe, 2016. https://ri.ufs.br/handle/riufs/3526.
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Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPqThe objective of this work was to study NbAlN thin films and the influence of variation in the concentration of aluminum in the crystal structure, mechanical properties and oxidation resistance of these coatings. The thin films were deposited by reactive magnetron sputtering and characterized by Grazing Incidence X-ray Diffraction (GIXRD), Energy Dispersive Spectroscopy (EDS), Rutherford Backscattering Spectrometry (RBS), nanohardness analysis and oxidation tests at high temperatures. It was first necessary to define the deposition parameters of NbN thin films with δ-NbN phase (fcc). From this, NbAlN thin films were deposited and present at concentration of 10, 20 and 42 at% Al. The NbAlN crystalline phase obtained was the δ-NbN, however it was observed a shift of the peaks in the patterns obtained GIXRD of regions for larger angles for these samples, indicating the formation of a solid solution. The higher oxidation resistance temperature was 700° C for the sample with 42 in at% Al. From the SEM analysis it was possible to observe the surface of the film after oxidation, all films showed defects, however the amount of such defects was lower in samples with higher aluminum concentrations. The average hardness values obtained for thin films NbAlN was 25 GPa.
O objetivo do presente trabalho foi estudar filmes finos de NbAlN e verificar a influência da variação da concentração de alumínio na estrutura cristalina, propriedades mecânicas e resistência à oxidação desses revestimentos. Os filmes finos foram depositados por magnetron sputtering reativo e caracterizados por Difração de Raios X em Ângulo Rasante (GIXRD), Espectroscopia de Energia dispersiva (EDS), Espectroscopia por Retroespalhamento Rutherford (RBS), análises de nanodureza e testes de oxidação a altas temperaturas. Primeiramente foi necessário definir os parâmetros de deposição de filmes finos de NbN com fase δ-NbN (cfc). A partir disso, filmes finos de NbAlN foram depositados e apresentaram concentração em at% de Al de 10, 20 e 42. A fase cristalina obtida para os filmes de NbAlN foi a δ-NbN, entretanto foi observado um deslocamento dos picos obtidos nos padrões de GIXRD para regiões de ângulos maiores para essas amostras, o que indica a formação de uma solução sólida. A maior temperatura de resistência à oxidação foi de 700°C para a amostra com 42 at% de Al. A partir das análises de MEV foi possível observar a superfície dos filmes após a oxidação, todos os filmes apresentaram defeitos, entretanto a quantidade desses defeitos foi menor nas amostras com maiores concentrações de alumínio. Os valores médios de dureza obtido para os filmes finos de NbAlN foi de 25 GPa.
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Alves, Luiz Antonio. "Propriedades óticas de filmes de nitreto de titânio com adição de nióbio depositados por triodo-magnetron sputtering." Universidade do Estado de Santa Catarina, 2014. http://tede.udesc.br/handle/handle/619.
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Titanium nitride (TiN) films with niobium (Nb) addition (TiN[Nb], 0,01 < Nb/Ti < 0,15) were obtained by sputter deposition in a triode magnetron sputtering system from a mosaic target of titanium with niobium inserts at the erosion zone. The effects of Nb/Ti in surface morphology were analyzed by atomic force and confocal microscopy measurements. The reflectivities of the films with niobium incorporation are in agreement with the Drude-Lorentz model. The constants obtained by the fitting show an increase in plasma frequency and relaxation time with increased Nb/Ti ratio, indicating an increase in the number of charge carriers. The color parameters according CIELab system show an increase in L*, a* and b* coordinates. The visual analysis indicates an increased red tone when compared with pure TiN film in agreement with the increased absolute values of a* coordinates.
Filmes de nitreto de titânio com adição de nióbio ((TiN[Nb], 0,01 < Nb/Ti < 0,15) foram depositados pelo processo de pulverização catódica utilizando um sistema Triodo Magnetron Sputtering. A pulverização catódica de Titânio e Nióbio foi feita a partir de um alvo de titânio com insertos de nióbio dispostos na região de erosão. Foram analisados os efeitos da razão Nb/Ti na morfologia superficial do filme através de microscopia de força atômica e confocal. As medidas de refletividade dos filmes de TiN[Nb] obedecem perfeitamente o modelo de Drude-Lorentz. As constantes obtidas pelo modelo de Drude-Lorentz mostram um aumento nos valores da frequência de plasma e tempo de relaxação com o aumento na razão Nb/Ti, indicando que a presença de nióbio aumenta o número de portadores de carga. Os parâmetros de cor segundo o sistema CIELab mostram um aumento nas coordenadas L*, a* e b*. A análise visual das amostras mostra uma tonalidade avermelhada, quando comparadas com o filme contendo somente TiN, em concordância com o aumento absoluto nas coordenadas a*.
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Norlin, Anna. "Investigation of electrochemical properties and performance of stimulation/sensing electrodes for pacemaker applications." Doctoral thesis, Stockholm, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-176.
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Jan, Jin-Shyong. "All niobium nitride Josephson vortex flow transistor." 1990. http://catalog.hathitrust.org/api/volumes/oclc/22806461.html.
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Thesis (Ph. D.)--University of Wisconsin--Madison, 1990.Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 211-219).
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Bedorf, Sven Holger [Verfasser]. "Development of ultrathin niobium nitride and niobium titanium nitride films for THz hot-electron bolometers / vorgelegt von Sven Holger Bedorf." 2005. http://d-nb.info/978280849/34.
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Li, Yen-Jun, and 李彥濬. "Phase and superconductivity studies of micro-sized niobium nitride." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/ar2242.
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碩士國立政治大學
應用物理研究所
106
Niobium nitride is a low compressibility and high hardness material. It has many phases structures, including cubic δ-NbN, ε-hexagonal, δ’-hexagonal and tetragonal. In this work, we investigate the appearance of superconductivity of each NbN phase. Pure cubic δ-NbN specimens were prepared by annealing 1400 oC from NbN powder of Alfa Aesar. The lattice constant of this specimen was determined to be 4.385 Å by powder X-ray diffraction (XRD) measurement. Superconductivity of Cubic δ-NbN phase was revealed at 13.4 K by the measurements of resistivity magnetic susceptibility and heat capacity of pressed powders. It is consistent with previous reports that Tc is a function of lattice constant. Zou et. al. reported that two superconducting temperatures of 17.1 K and 10.1 K appear in the powder of Goodfellow, they claimed 17.1 K is of cubic phase and 10.1 K is of ε-hexagonal phase. We also observed two Tc from the powder of Goodfellow, based on X-ray and magnetic data the Tc =17.1 K is defined from cubic phase, but the phase of Tc =10.1 K is hardly fitted to the ε-hexagonal phase. In order to check whether ε-hexagonal phase have superconductivity or not, a sub-micron particles of single crystal was selected from the powder of Goodfellow, the ε-hexagonal phase of the particle is revealed by the measurements of EBSD (Electron Back Scattering Diffraction). The resistivity measurement of the sub-micro crystal shows no superconductivity as temperature down to 2 K. We also measured the specific heat of cubic NbN from pressed powder of Alfa Aesar. The superconductivity transition temperature Tc =11 K was observed. The electronic part of specific heat, ΔC/γTc is equal to 0.83 which is lower than BCS value, 1.43, indicating an unusual superconductivity. The critical field of superconductivity Hc1 obtained from the magnetic field dependent magnetization is 185 Oe. The Hc2 obtained from magneto resistivity data is 19.22 T. A sub-micron size δ-cubic crystal successfully selected from Alfa Aesar powder was confirmed by EBSD, Tc=13 K and Hc2 =21.3 T were obtained from resistivity measurements, the results are in consistent with that obtained from χ(T) and R(T) of the pressed powder specimen.
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Lin, Shin Yu, and 林信宇. "Investigation on characteristics of niobium nitride and molybdenum nitride gates on hafnium oxide gate dielectrics." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/91108897930458042664.
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碩士國立聯合大學
材料科學工程學系碩士班
99
In this study, niobium nitride (NbNx) and molybdenum nitride (MoNx) thin films are deposited by magnetron sputtering on various thicknesses of HfO2 gate dielectrics (i.e., 2 nm, 4 nm, 6 nm, 8 nm, and 12 nm) to fabricate the metal/oxide/semiconductor capacitors. The incorporation of nitrogen into the NbNx and MoNx films is controlled by N2/(Ar+N2) flow ratios. The Nb/NbNx and Mo/MoNx gate stacks are deposited on HfO2, and followed by forming gas annealing (FGA) at 400oC for 30 min. The characteristics of Nb/NbNx and Mo/MoNx thin films deposited with various N2/(Ar+N2) flow ratios, before and after FGA, are examined. In addition, the effective work functions (Φm) of gate electrodes are also extracted from capacitance-voltage (C-V) curves to discuss the relation between material properties and the shift of Φm. The thicknesses and surface morphology of NbNx and MoNx films are determined by field emission scanning electron microscopy (FESEM). The crystal structure is identified by grazing incidence angle x-ray diffractometer (GIAXRD). The composition and chemical bonding of NbNx and MoNx films are tailored by X-ray photoelectron spectroscopy (XPS). For electrical properties, the resistivity is measured by four point probe, and C-V curves are obtained by using the LCR meter (Agilent E4980A) to extract the Φm. The SEM and GIAXRD results show that the morphology and crystal structure of NbNx and MoNx films exhibit a transition when the N2/(Ar+N2) flow ratio is more than 2%. The surface morphology changes from polyhedron to slab, and the phase changes from body-centered- cubic to face-centered- cubic structure. The NbNx structure is becoming nearly amorphous when the N2/(Ar+N2) flow ratio increases, whereas the MoNx structure shows increased crystallinity. Moreover, the resistivity of MoNx films, before and after FGA, is lower than that of NbNx films using the same deposition parameters. The results reveal that the Φm of NbNx films ranges from 3.83 eV to 4.17 eV, and that of MoNx films ranges from 4.58 eV to 5.23 eV. It suggests that the Φm can be modulated by the nitrogen content. Consequently, the NbNx and MoNx gate electrodes are promising for applications in n-channel and p-channel metal-oxide-semiconductor field-effect transistors, respectively.
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Zhuang, Yan. "Linear and nonlinear characteristics of niobium nitride hot-electron bolometer devices." 2002. https://scholarworks.umass.edu/dissertations/AAI3068608.
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The superconducting HEB device is so far the most promising low noise mixer in the THz frequency range. It out-performs other existing receiver systems because it has low noise temperature and sufficient bandwidth for applications in the FIR range such as astronomy, remote sensing and plasma diagnostics. This work investigates the linear and nonlinear characteristics of NbN Hot Electron Bolometer (HEB) devices. First of all, a thorough expression of the Johnson noise and the thermal fluctuation noise has been re-derived. Our circuit model is more preferable for the HEB devices than the traditional one being used for the semiconductor bolometer. Secondly, the equivalent noise temperature of our receiver system has been significantly improved: the noise temperature went from the original 5800K to a record of 500K for silicon substrate devices. We are also getting improved noise performance for the new MgO substrate devices. The simulation results agree with the measured data very well around the optimum operating point. Finally, the device in the unstable region can be stabilized by connecting a series resistor with higher resistance than the negative resistance of the device. Two frequencies are related to the oscillation waveforms of the voltage and the current of the device. The first one is the repetition frequency that is actually related to the external circuit. The second one is the relaxation frequency that is related to the intrinsic phenomena of the device itself. The domain wall velocity and the relaxation oscillation frequency have been calculated both theoretically and experimentally. The calculated results are within a satisfactory range compared with the measured data. Also, a thorough explanation of the device oscillation process has been presented.
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Chown, Lesley H. "The influence of continuous casting parameters on hot tensile behaviour in low carbon, niobium and boron steels." Thesis, 2009. http://hdl.handle.net/10539/6499.
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Abstract
This thesis studies the factors that govern transverse cracking during continuous casting
of low carbon, niobium microalloyed and boron microalloyed steels. Crack susceptibility
in the thick slab, billet and thin slab casting processes are compared by using typical
conditions in laboratory hot ductility tests.
There is limited published literature on hot ductility in aluminium-killed and siliconkilled
boron microalloyed steels and the proposed mechanisms of failure by transverse
cracking are contradictory. Few published papers specifically compare hot ductility
behaviour of any steels between thick slab, billet and thin slab continuous casting
processes. Thus, the basis of this research is to assess the influence of casting parameters
and compositional variations on hot ductility behaviour in low carbon steels, niobium
microalloyed steels, aluminium-killed boron microalloyed steels and silicon-killed, boron
microalloyed steels.
The typical temperature ranges, cooling rate and strain rate conditions of the continuous
casting processes were used in reheated and in situ melted hot tensile tests performed on
steel specimens. Solidification, transformation and precipitation temperatures were
calculated using solubility equations and modelled using the Thermo-CalcTM
thermodynamics program. Scanning electron microscopy and transmission electron
microscopy were used to determine the modes of failure in the tested specimens.
In the low carbon steels, hot ductility was improved by increasing the strain rate; by
calcium treatment, which minimises copper sulphide and iron sulphide formation; and by
maintaining a nickel to copper ratio of 1:1. It was shown that thin slab casting conditions
provided the best hot ductility results for the low carbon steels.
All the niobium steels showed poor ductility in the single-phase austenite temperature
region, indicating that intergranular precipitation of fine niobium carbonitrides was the
cause of the poor ductility. It was shown that the hot ductility was greatly improved by
calcium treatment, by decreasing the cooling rate and by increasing the strain rate. Slow
iv
thin slab and thick slab casting conditions provided the best hot ductility results for the
niobium steels.
Hot ductility was substantially improved in the aluminium-killed boron steels by
increasing the boron to nitrogen ratio from 0.19 to 0.75. The results showed that, at
cooling rates generally associated with thick slab, bloom and slow thin slab casting, a
boron to nitrogen ratio of ≥0.47 was sufficient to avoid a ductility trough altogether.
However, under conditions typically experienced in fast thin slab and billet casting, a
boron to nitrogen ratio of 0.75 was required to provide good hot ductility. The mechanism
of the ductility improvement with increasing boron to nitrogen ratio was found to be
enhanced precipitation of boron nitride, leading to a decrease in nitrogen available for
aluminium nitride precipitation.
In the silicon-killed boron steels, it was found that the boron to nitrogen ratio had the
overriding influence on hot ductility and hence on crack susceptibility. Excellent hot ductility
was found for boron to nitrogen ratios above 1. Additionally, analysis of industrial casting data
showed that the scrap percentage due to transverse cracking increased significantly at
manganese to sulphur ratios below fourteen. An exponential decay relationship between the
manganese to sulphur ratio and the average scrap percentage due to transverse cracking was
determined as a tool to predict scrap levels in the casting plant.
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Gerecht, Eyal. "Development of niobium nitride hot electron bolometric mixer for terahertz frequencies: The phonon-cooled version." 1998. https://scholarworks.umass.edu/dissertations/AAI9841871.
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NbN HEB mixers represent a promising approach for achieving receiver noise temperatures of a few times the quantum noise limit at frequencies above 1 THz. NbN HEB devices have been shown to have sufficient bandwidth for applications in astronomy, remote sensing, and plasma diagnostics in the FIR range. The NbN HEB is a phonon cooled bolometer in which the energy is transfered from the hot electrons to the substrate via inelastic collisions with phonons. The development of an NbN HEB mixer contained two steps: (1) implementing mixing in a comparatively large "direct-coupled" prototype device which required LO power of a few milliwatts, and (2) optimization of the first step by the development of an "antenna-coupled" (quasi-optically coupled) device with an LO power level of less than one $\mu W$. The LO power was coupled to the antenna via an extended hemispherical lens (1.3 mm in diameter). The design, fabrication, and measurement stages were performed by a collaborative effort between a Russian team from the Department of Physics at Moscow State Pedagogical University in Moscow, the Submillimeter Technology Laboratory at UMass/Lowell and the Department of Electrical and Computer Engineering at UMass/Amherst. Mixing at 2.5 THz was demonstrated for the first time using the direct-coupled device achieving an intrinsic conversion loss of 23 dB. Sufficient level of LO power coupling at four different frequencies was demonstrated with the antenna-coupled device. The antenna/lens configuration has performed as well as expected insuring coupling to LO power of less than one $\mu$W. A 3 dB conversion gain was demonstrated with the antenna-coupled device using a laser LO at 1.56 THz with an IF frequency of 500 KHz. A second laser was utilized as the rf source. Noise temperature for the NbN HEB mixer receiver of 5800 K has been demonstrated over the 1.25-1.75 GHz IF band. The mixer temperature was 2500 K and the total conversion loss was 27 dB. Further optimization of the receiver configuration and device fabrication as well as additional development in mixer modeling will gradually lead to lower noise temperatures.
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Baunemann, Arne [Verfasser]. "Precursor chemistry of tantalum and niobium nitride for MOCVD and ALD applications / vorgelegt von Arne Baunemann." 2006. http://d-nb.info/982633009/34.
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Yi-RuWu and 吳佾儒. "Wear performance of micro-drills with amorphous carbon nitride (a-C:N) coatings doped with hydrogen and niobium." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/8dafa3.
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Krishnan, R. "Investigations On The Properties Of TiN, NbN Thin Films And Multilayers By Reactive Pulsed Laser Deposition." Thesis, 2010. http://etd.iisc.ernet.in/handle/2005/2274.
Full textAbstract:
Two technologies, namely Laser Technology and Surface Modification Technology, have made rapid strides in the last few decades. The lasers have evolved from a simple laboratory curiosity to a matured industrial tool and its applications are limited only by imagination. Intense, coherent and monochromatic laser sources with power outputs ranging over several orders of magnitude have found innumerable applications in the realm of materials engineering. Reactive Pulsed Laser Deposition (PLD) is a powerful technique that utilises the power of a nanosecond pulsed laser for materials synthesis. Unlike conventional PLD, which require high density targets that are difficult to synthesize at a reasonable cost, the RPLD circumvents the need for one such ceramic target. This thesis presents a detailed and judicious use of this technique for synthesis of hard ceramic multilayer coatings using elemental metal targets.
Transition metal nitrides having rock salt structure are known to exhibit superior properties such as hardness and wear resistance and hence formed the basis for the development of first generation coatings. Further improvements through alloying of these binary compounds with metal or metalloid components lead to the development of second generation coatings. As the demand for functional materials increased, surface modification technology alias surface engineering, grew in leaps and bounds. As the large number of coating requirements for optimal performance could not be fulfilled by a single homogeneous material, third generation coatings, comprising multilayer coatings, were developed. It is this aspect of combining the advantages of RPLD process to synthesize ceramic multilayer coatings, provides the main motivation for the present research work.
In this thesis, a systematic study presented for synthesis of nanocrystalline and stoichiometric TiN and NbN thin films using RPLD through ablation of high purity titanium and niobium targets, in the presence of low pressure nitrogen gas. A novel Secondary Ion Mass Spectrometry (SIMS) based analysis was developed to effectively deduce the important process parameters in minimum trials to arrive at desired composition. The validity of this SIMS based method, for optimization of process parameters to get stoichiometric nitride films, was proved beyond any speculation by corroborative Proton Elastic Backscattering Spectrometric (PEBS) analysis. SIMS was also used to characterize the [NbN/TiN] multilayers. The feasibility of growing nanocrystalline multilayers with varying thicknesses has been demonstrated. Nanomechanical properties including hardness and adhesion strength of monolithic TiN and NbN films and multilayers were evaluated.
The thesis is organised into six chapters. The first chapter gives a brief account on the history and development of ‘surface engineering’. The second chapter provides a comprehensive description of the experimental facility developed in-house to pursue research on PLD grown ceramic thin films and multilayers. Thin film synthesis procedure for ex-situ SIMS and TEM analyses is described. Brief introduction is also presented on the characterization techniques used in this study to investigate the surface, interface and microstructural aspects of PLD grown films with underlying basic principles. The third and fourth chapter describes the synthesis and characterization of titanium nitride and niobium nitride thin films using RPLD technique, respectively. SIMS was used in depth profiling mode, for optimization of three important process parameters, viz., nitrogen gas pressure, substrate temperature and laser pulse energy, to get stoichiometric nitride films. Further, films were characterized using GIXRD, TEM, XPS and PEBS for their structure and composition. AFM measurements were made to elucidate the surface morphological features. PEBS was effectively used to estimate the nitrogen concentration in a quantitative manner and the results corroborate well with the SIMS measurements. Having succeeded in synthesizing stoichiometric TiN and NbN films, further studies on the nanomechanical properties of monolithic TiN and NbN films and their multilayers were carried out and these results form the contents of the fifth chapter. The findings of the work reported in this thesis are concluded in Chapter 6 and few possible suggestions were presented as future directions.
Both the monolithic TiN and NbN coatings showed a deposition pressure dependent hardness variation. The hardness of these monolithic films was found to be around 30 GPa, higher than the hardness values obtained by other conventional techniques. Keeping total thickness of the multilayers constant at 1 μm, [NbN/TiN] multilayers having bilayer periods ranging from 50 nm to 1000 nm, were synthesized. A systematic enhancement in hardness upto ~ 40 GPa was observed for [NbN/TiN]10 with the modulus of the multilayer remaining almost constant. The pileup observed around the indentation edge is indicative of toughening in multilayers. The tribological properties of multilayer films showed a better performance in terms of low coefficient of friction and regeneration of coating surfaces as revealed from the nanotribological studies. Overall, the multilayer coatings exhibited better performance in terms of hardness, toughness and adhesion with the substrate material.
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Yin-HsiangMao and 毛胤翔. "Titanium Addition of Niobium Nitride Single and Multilayer Coating on Wear Property, Corrosion Resistance and Applications on High Speed Drills after Acetylene Introduction." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/2vvdbb.
Full textAbstract:
碩士國立成功大學
機械工程學系
107
This study was composed of three stages. In first stage, NbNxA coatings were prepared by DC magnetron sputtering. In second stage, NbTi-NX and NbN/TiNxmin coatings were prepared using RF magnetron sputtering. In third stage, acetylene was introduced to prepare NbTi-NX-CH coating. Considering wear property and corrosion resistance, NbTi-N12-CH coating was the optimal parameter for preparation in this research. Applied the NbTi-N12-CH coating to a high-speed drill and tested it by drilling 2000, 4000, and 6000 holes. The results revealed that applying this coating to the drill could increase its drill life to 4000 holes, which is two times longer than that of an uncoated drill.