Publications

2006

• Etude et mise au point de ferrites à basse température de frittage pour la réalisation de composants hyperfréquences intégrés.
  
  • Pinier Ludovic
  , 2006. Le but du travail entrepris ici est d'étudier et d'élaborer des matériaux magnétiques pour applications micro-ondes, notamment pour la réalisation de dispositifs de type circulateur. Mais parmi les applications nécessitant de tels matériaux, on peut également citer les déphaseurs. Si l'essentiel du travail ne porte pas sur l'amélioration des performances des composants en termes de pertes d'insertion et d'isolation, d'autres points apparaissent comme pouvant donner lieu à des évolutions notables. C'est pourquoi nous nous proposons ici d'orienter le travail plus sur les aspects de mise en œuvre du matériau. L'objectif poursuivi tout au long de cette thèse est double : à la fois scientifique et technologique. En effet, l'amélioration que nous nous proposons d'apporter par nos matériaux n'est pas anodine et si cela a des intérêts du point de vue des procédés technologiques, c'est aussi l'occasion d'une réflexion sur le matériau en lui-même, et les mécanismes chimiques qui lui confèrent ses propriétés particulières. D'autre part, la fabrication d'un composant comme le circulateur est un processus complexe. Ce dispositif est un assemblage délicat de différents matériaux qui, à l'heure actuelle, est difficilement automatisable. L'intervention humaine nécessaire à l'assemblage limite par conséquent la miniaturisation de ce composant.
• Couplage interplan dans Bi2Sr2CaCu2O8+∂ : effet du désordre et du champ magnétique
  
  • Spathis Panayotis
  , 2006. La résonance plasma Josephson a permis de détecter précisément l'évolution de la densité suprafluide hors plan dans le Bi2Sr2CaCu2O8+∂ sous-dopé en fonction du désordre cristallin. La comparaison avec plusieurs résultats de la littérature a permis de montrer que le transport des charges est réalisé par effet Josephson incohérent par opposition au cas optimalement dopé. Tandis que l'évolution des propriétés supraconductrices au sein des plans est bien interprétée dans le cadre de la théorie d'Abrikosov Gor'kov, le transport interplan des paires de Cooper est assuré par diffusion anisotrope dans la limite de Born sur les défauts présents entre les couches CuO2. Ce résultat est en accord avec la récente proposition qui relie les modulations spatiales du gap supraconducteur à la présence des défauts d'oxygène entre les plans. Concernant les propriétés de l'état mixte, la résonance plasma a pu montrer que le rajout d'une composante parallèle aux plans CuO2 du champ magnétique à un liquide de pancakes, permet d'induire des corrélations spatiales. Cet effet est dû à la réorganisation des courants supraconducteurs. Là encore, seule la résonance plasma Josephson permet de sonder l'état liquide des vortex en raison de sa grande fréquence par rapport aux mouvement de vortex.
• Micro-Raman studies on 50 keV electron irradiated silicate glass
  
  • Ollier N.
  • Gedeon O.
  Journal of Non-Crystalline Solids, Elsevier, 2006, 352 (50-51), pp.5337-5343. A potassium-lime-silicate glass was irradiated with a 50 keV electron beam. The impact of irradiation conditions on the glass structure (beam diameter, current, and irradiation time) was studied by Micro-Raman spectroscopy. For irradiation time less than the incubation time (around 360 s), structural evolutions are attributed to a glass densification. Irradiations longer than the incubation period led to a precipitation of supposed calcium enriched phase and formation of a more depolymerized silicate phase. A non-homogeneous irradiated glass structure was observed with the existence of an area (along the electron beam border) composed by a mixture of a concentrated Ca phase diluted into the amorphous silicate phase. (c) 2006 Elsevier B.V. All rights reserved. (10.1016/j.jnoncrysol.2006.08.026)
  DOI : 10.1016/j.jnoncrysol.2006.08.026
• Ab initio study of Γ − X intervalley scattering in GaAs under pressure
  
  • Sjakste Jelena
  • Tyuterev Valeriy
  • Vast Nathalie
  Physical Review B: Condensed Matter and Materials Physics (1998-2015), American Physical Society, 2006, 74 (23). (10.1103/PhysRevB.74.235216)
  DOI : 10.1103/PhysRevB.74.235216
• Modifications structurales et défauts ponctuels paramagnétiques induits par irradiation électronique externe de la hollandite Ba1.16Al2.32Ti5.68O16
  
  • Caurant D.
  • Aubin-Chevaldonnet Virginie
  • Gourier Didier
  • Charpentier Thibault
  • Esnouf Stéphane
  • Advocat T.
  , 2006. Des matrices BaxCsy (M,Ti)8O16 (x+y<2, M cation trivalent) de type hollandite, sont envisagées pour confiner spécifiquement le césium radioactif. Afin de simuler l'effet des rayonnements b, les modifications structurales et les défauts ponctuels paramagnétiques produits par irradiation électronique externe à température proche de l'ambiante d'une hollandite de composition simplifiée sans césium Ba1,16Al2,32Ti5,68O16 ont été étudiés par RPE et RMN. Des modifications ont été observées au niveau de l'environnement des cations Al3+ et Ti4+, résultant de la formation de lacunes d'oxygène et d'une augmentation du désordre dans les tunnels associée à des déplacements d'ions baryum. Des centres à électrons (Ti3+) et à trous électroniques (O2-) ont été observés. Ceux-ci sont relativement stables à température ambiante mais des recuits (traitements isochrones entre 50 et 800°C, traitements isothermes à 300°C) engendrent la formation d'autres défauts issus des défauts précédents correspondant à des ions Ti3+ de surface de type titanyl et des agrégats d'oxygène.
• Etude théorique des phases du titane
  
  • Trinite Virginie
  , 2006. L'objectif de cette thèse est d'aboutir à une meilleure compréhension du diagramme de phase du titane grâce à la théorie de la fonctionnelle de la densité. Ce diagramme comprend 3 phases: la phase alpha, la phase omega de haute pression et la phase beta de haute température. Ceci nécessite de pouvoir prédire les différences d'énergie entre phases avec une très grande précision, car ces écarts sont faibles, environ 50 meV. Or, les calculs ab initio prédisent la phase omega comme la phase la plus stable, en désaccord avec l'expérience. Ce problème existe aussi dans le dioxyde de titane et dans le zirconium. J'ai donc exploré les différentes approximations présentes afin de comprendre laquelle est en cause. Ceci m'a conduite à étudier l'influence des états de semi-coeur et de la fonctionnelle d'échange et corrélation, et à évaluer la contribution de l'énergie de point zéro. J'en ai conclu que c'est l'approximation de la fonctionnelle qui engendre une erreur significative. Une correction possible consiste à tenir compte de l'auto-interaction électronique. Cette correction appliquée aux états de semi-coeur améliore systématiquement les paramètres de maille, mais n'explique pas l'erreur sur la stabilité des phases. Bien que les fonctionnelles d'échanges et corrélation usuelles ne se soient pas révélées suffisamment précises pour décrire le diagrammes de phases du titane, elles sont satisfaisantes pour prédire des propriétés moins fines, comme les constantes élastiques. Toutefois, il est nécessaire que le volume d'équilibre prédit soit précis, car j'ai mis en évidence que ces propriétés dépendent fortement du volume
• Etude ab initio et simulation à l'Echelle atomique des transitions de phase du titane.
  
  • Trinite-Quequet Virginie
  , 2006. L'objectif de cette thèse est d'aboutir à une meilleure compréhension des propriétés des différentes phases du titane. L'étude du titane est im- portante du point de vue fondamental car la compréhension des éléments correspondant au remplissage de la couche 3d est encore loin d'être satis- faisante. Le titane est l'un des premiers éléments de transition. Il possède un nombre encore raisonnable d'électrons à modéliser, tout en présentant les difficultés liées à la modélisation de la couche 3d. Quand les problèmes de modélisation rencontrés ne sont pas spécifiquement liés au titane, mais représentent une tendance générale parmi les éléments de transition, nous étendons notre analyse à d'autres matériaux comme le dioxyde de titane, le cuivre ou le zirconium.
• Cation Complexation Properties of Hexakis(2- O -methyl-3,6-anhydro)-α-cyclodextrin: A 1 H NMR Study
  
  • Fauvelle Florence
  • Gadelle A.
  • Debouzy J.
  • Baudin C.
  • Perly B.
  Supramolecular Chemistry, Taylor & Francis: STM, Behavioural Science and Public Health Titles, 2006, 11 (3), pp.233-237. The affinity of hexakis(2-O-methyl-3,6-anhydro)-α-cyclodextrin (3,6-α-CDM) for Ba2+, Pb2+, Ca2+ and Sr2+ has been tested by 1H NMR. It was shown that 3,6-α-CDM forms strong complexes in water with Pb2+ and Ba2+. The comparison with the parent hexakis(3,6-anhydro)-α-cyclodextrin bearing hydroxyl groups instead of methoxy groups reveals that the O-CH3 substitution significantly improves the anhydro-cyclodextrin selectivity. (10.1080/10610270008049133)
  DOI : 10.1080/10610270008049133
• Structural evolutions of a borosilicate glass induced by heavy ions
  
  • Gaillard Marina
  • Peuget S.
  • Charpentier Thibault
  • Boizot Bruno
  • Ollier Nadège
  • Noël Py
  , 2006. High-level nuclear waste containment glass is subjected to irradiation-induced stresses whose consequences must be assessed to guarantee the material behavior over time. Alpha decay from the minor actinides confined in the glass structure is responsible for most of the atom displacements. Radiation studies of nuclear glasses have shown some slight evolutions of some macroscopic properties (density, mechanical properties). The understanding of the structural origin of these modifications is important for the modeling of the long term behavior of such materials. A powder of simplified borosilicate glass composition was irradiated by multi energies gold ions to simulate the effect of alpha decay. The irradiation conditions were defined to induce a constant nuclear interaction in the grains of diameter around 2µm. For these irradiations conditions, the hardness of the glass decreased by 35%. Structural characterizations of the pristine and irradiated powders were made by multinuclear (11B, 23Na, 27Al, 29Si) Magic Angle Spinning Nuclear magnetic Resonance (NMR) and RPE to try to identify the structural origins of the macroscopic modification observed. It is observed that the local environment of boron and sodium are highly influenced by the irradiation with an important increase of boron tri-coordinated and a significant modification of the sodium cations organization. The NMR silicon spectra show fewer evolutions but a slight shift is observed that may indicate a less polymerized silicate network
• New sulfonated pyrrole and pyrrole 3-carboxylic acid copolymers membranes via track-etched templates
  
  • Clochard M.-C.
  • Baudin C.
  • Betz N.
  • Le Moël A.
  • Bittencourt C. C.
  • Houssiau L.
  • Pireaux J.-J.
  • Caldemaison Daniel
  , 2006. New copolymers of polypyrrole and poly(3-carboxylic acid pyrrole) have been synthesized via diaphragmatic method using track-etched polycarbonate matrix. The carboxylic acid presence permits to introduce new functionalities such as sulfonate groups. The resulted copolymer membranes with tubules microstructure has been characterized by Scanning Electron Microscopy, X-ray Photoelectron Spectroscopy, Time-of-flight Secondary Ion mass Spectrometry and FTIR. By SEM it was observed that ion-track trajectories present characteristic of crossing. FTIR, XPS and ToF-SIMS proved the attachment of the Taurin molecule to the membrane. The thermal stability study shows that the polypyrrole copolymer membranes have an exceptional stability; decomposition was not observed up to 900°C.
• Dependence of the irradiation-induced growth kinetics of satellites on the nanoclusters dimension
  
  • Rizza G.
  • Ramjauny Y.
  • Gacoin T.
  • Henry S.
  , 2006, 257, pp.15-19. Irradiation with MeV gold ions of embedded Au nanoclusters in silica matrix results in the formation of a ring of satellites in its surrounding. We show that changing the initial nanoclusters size modifies both the size and the density of the satellites, and therefore alters their kinetic growth. Finally we discuss the limitation of the ion implantation technique to form a model system to study the satellites kinetic growth and we propose a new approach based on the chemical synthesis of metallic nanoparticles to obtain the proper configuration. (10.1016/j.nimb.2006.12.113)
  DOI : 10.1016/j.nimb.2006.12.113
• Predictive factors for thrombosis and major bleeding in an observational study in 181 patients with heparin-induced thrombocytopenia treated with lepirudin.
  
  • Tardy Bernard
  • Lecompte Thomas
  • Boelhen Françoise
  • Tardy-Poncet Brigitte
  • Elalamy Ismaïl
  • Morange Pierre-Emmanuel
  • Gruel Yves
  • Wolf Martine
  • Francois Dominique
  • Racadot Evelyne
  • Camarasa Philippe
  • Blouch Marie Thérèse
  • Nguyen Françoise
  • Doubine Sylvie
  • Dutrillaux Fabienne
  • Alhenc-Gelas Martine
  • Martin-Toutain Isabelle
  • Bauters Anne
  • Ffrench Patrick
  • de Maistre Emmanuel
  • Grunebaum Lélia
  • Mouton Christine
  • Huisse Marie G
  • Gouault-Heilmann Michèle
  • Lucke Veronique
  • Renseigné Non
  Blood, American Society of Hematology, 2006, 108 (5), pp.1492-6. The antithrombotic efficacy of lepirudin in patients with heparin-induced thrombocytopenia (HIT) is compromised by an increased risk for bleeding. A retrospective observational analysis in 181 patients (median age, 67 years) with confirmed HIT treated in routine practice with lepirudin was performed to identify predictive factors for thrombotic and bleeding complications. Lepirudin was administered at a mean (+/- SD) dose of 0.06 +/- 0.04 mg/kg/h (compared with a recommended initial dose of 0.15 mg/kg/h). Mean activated partial thromboplastin time was greater than 1.5 times baseline value in 99.4% of patients. Median treatment duration was 7.7 days. Until discharge from the hospital, 13.8% and 20.4% of patients experienced a thrombotic or a major bleeding event, respectively. On multivariate analysis, mean lepirudin dose was not a significant predictive factor for thrombosis. In contrast, mean lepirudin dose greater than 0.07 mg/kg/h, long duration of lepirudin treatment, and moderate to severe renal impairment were significant positive factors for major bleeding. Overall, these results suggest that the recommended dose of lepirudin in patients with HIT is too high; the use of reduced doses may be safer with regard to bleeding risk and does not compromise antithrombotic efficacy. (10.1182/blood-2006-02-001057)
  DOI : 10.1182/blood-2006-02-001057
• Phenomenological model of damage creation by high electronic excitations in pure metals
  
  • Dammak H.
  • Lesueur D.
  • Dunlop A.
  • Legrand P.
  • Morillo Joseph
  Radiation Effects and Defects in Solids, Taylor & Francis, 2006, 126 (1-4), pp.111-114. (10.1080/10420159308219689)
  DOI : 10.1080/10420159308219689
• Energetic cluster irradiation of InP
  
  • Dhamodaran S.
  • Pathak A.P.
  • Dunlop A.
  • Jaskierowicz G.
  • Della Negra S.
  , 2007, 256, pp.229-232. The track formation in semiconductors has been studied for over last ten years. The threshold electronic energy loss required to create tracks in semiconductors is relatively larger than in insulators. Among semiconductors, track formation in InP by monoatomic ion irradiation has been studied extensively. This work presents new results concerning the creation of tracks in a semiconductor, InP, irradiated at room temperature with energetic heavy cluster ions. Samples prepared for transmission electron microscopy (TEM) observations were irradiated with 23–40 MeV C60 ions at fluences of the order of 1010 ions cm−2. During the slowing-down of such projectiles in the targets, energy is mainly lost in electronic excitation and ionisation. It should be noted that the corresponding energy densities are one order of magnitude higher than those obtained using GeV monoatomic ions as projectiles, which leads to very strong structural modifications. Track diameters have been measured for three different ion energies and compared to previous results obtained with monoatomic ions. We also analyse our results using thermal spike model (TSM) proposed by Szenes for track formation and address its validity for such studies. The analysis highlights the doubt on the basic assumptions of the model and its applicability particularly for the case of cluster irradiations. (10.1016/j.nimb.2006.12.009)
  DOI : 10.1016/j.nimb.2006.12.009
• Polarization - dependent tunneling of light in gradient optics
  
  • Shvartsburg Alexander
  • Kuzmiak Vladimir
  • Petite Guillaume
  , 2006. Reflection-refraction properties of photonic barriers, formed by dielectric gradient nanofilms, for inclined incidence of both S- and P-polarized electromagnetic (EM) waves are examined by means of exactly solvable models. We present generalized Fresnel formulae, describing the influence of the non-local dispersion on reflectance and transmittance of single- and double-layer gradient photonic barriers for S- and P- waves and arbitrary angles of incidence. The non-local dispersion of such layers, arising due to a concave spatial profile of dielectric susceptibility across the plane film, is shown to result in a peculiar heterogeneity - induced optical anisotropy, providing the propagation of S(P) waves in tunneling (travelling) regimes. The results obtained indicate the possibility of narrow-band non-attenuated tunneling (complete transmittance) of oblique S- waves through such heterogeneous barriers, and the existence of spectral areas characterized by strong reflection of P-waves and deep contrast between transmitted S- and P-waves. The scalability of obtained exact analytical solutions of Maxwell equations into the different spectral ranges is discussed and the application potential of these phenomena for miniaturized polarizers and filters is demonstrated.
• Direct Evidence for Trivalent Titanium in Artificially Irradiated (electrons) Oxide Glasses
  
  • Ollier N.
  • Farges Francois
  • Boizot Bruno
  • Lombard Pierre
  • Marie Flank Anne
  • Lagarde P.
  , 2006, 882, pp.523-525. Ti-doped borosilicate and disilicate glasses were irradiated with high-energetic electrons in order to study Ti(IV) reduction processes. Reduction efficiency was actually confirmed by an important Ti(III) EPR signal around g=1.93 in irradiated samples. The Ti(III) amount increases with the irradiation dose. Moreover, the Ti(Ill) environment depends on the glass composition. Hence, the reduction process efficiency is strongly correlated to the Ti(IV) environment in the pristine glass. The Ti environment was analyzed by Ti K-edge XANES in order to understand the reduction mechanisms. Pre-edge analysis of non-irradiated samples indicates the presence of four, five and six coordinated tetravalent Ti sites in borosilicate glasses, whereas in disilicate the Ti(IV) coordination is a mixture between five-fold and six-fold. In irradiated samples, the Ti pre-edge shows a slight low-energy shift associated to an intensity decrease in disilicate glasses. Correlation between EPR and XANES experiments allows for interpretation of the pre-edge variation in terms of Ti(III) formation. Profiles (gin resolution) were also performed to measure the proportion of Ti(HI) on different points across the irradiated DS. No significant difference in XANE S spectra was observed suggesting that the production of Ti(III) is homogeneous in the volume. (10.1063/1.2644580)
  DOI : 10.1063/1.2644580
• Role of pair-breaking and phase fluctuations in c-axis tunneling in underdoped Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+\delta}$
  
  • van Der Beek Cornelis Jacominus
  • Spathis Panayotis
  • Colson Sylvain
  • Gierlowski Piotr
  • Gaifullin Marat
  • Matsuda Yuji
  • Kes Peter H.
  , 2007, 460-462, pp.876-877. The Josephson Plasma Resonance is used to study the c-axis supercurrent in the superconducting state of underdoped Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+\delta}$ with varying degrees of controlled point-like disorder, introduced by high-energy electron irradiation. As disorder is increased, the Josephson Plasma frequency decreases proportionally to the critical temperature. The temperature dependence of the plasma frequency does not depend on the irradiation dose, and is in quantitative agreement with a model for quantum fluctuations of the superconducting phase in the CuO$_{2}$ layers. (10.1016/j.physc.2007.03.122)
  DOI : 10.1016/j.physc.2007.03.122
• Screening of transverse ac fields and influence of supercurrent on NMR Knight shift in high-Tc crystals
  
  • Yang Feng
  • van Der Beek Cornelis Jacominus
  • Shibauchi Takasada
  • Matsuda Yuji
  • Dabrowski Bogdan
  , 2007, 460-462, pp.929-930. In the Nuclear Magnetic Resonance (NMR) configuration with perpendicular constant (dc) field and radiofrequency (rf) magnetic field, a strong screening supercurrent is generated by the rf field. In order to estimate this current which may influence Knight shift data, we performed a model experiment in the NMR configuration on a YBa2Cu4O8 single crystal. The differential magneto-optical imaging technique is used to determine the ac screening current distribution in the sample. We find that at T > 20 K, NMR experiments can be straightforwardly interpreted. At T < 20 K, the rf field is completely excluded. In this situation, NMR only probes the crystal edges; moreover, the Knight shift may be affected by the supercurrent flow. (10.1016/j.physc.2007.03.386)
  DOI : 10.1016/j.physc.2007.03.386
• Composite to tilted vortex lattice transition in Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+\delta}$ in oblique fields
  
  • Konczykowski Marcin
  • van Der Beek Cornelis Jacominus
  • Koshelev Alexei E.
  • Mosser Vincent
  • Dodgson Matthew
  • Kes Pieter H.
  Physical Review Letters, American Physical Society, 2006, 97, pp.237005. Precision measurements of the vortex phase diagram in single crystals of the layered superconductor Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+\delta}$ in oblique magnetic fields confirm the existence of a second phase transition, in addition to the usual first order vortex lattice melting line $H_{m}(T)$. The transition has a strong first order character, is accompanied by strong hysteresis, and intersects the melting line in a tricritical point ($H_{m}^{\perp}$, $H^{\parallel}_{cr}$). Its field dependence and the changing character of the melting line at the tricritical point strongly suggest that the ground state for magnetic fields closely aligned with the superconducting layers is a lattice of uniformly tilted vortex lines. (10.1103/PhysRevLett.97.237005)
  DOI : 10.1103/PhysRevLett.97.237005
• In situ observation of beta-ray induced UV optical absorption in a-SiO2: Radiation darkening and room temperature, recovery
  
  • Agnello Simona
  • Cannas Marco
  • Messina Fabrizio
  • Nuccio Laura
  • Boizot Bruno
  Journal of Non-Crystalline Solids, Elsevier, 2006, 355 (18-21), pp.1042-1045. We studied the optical absorption in the 3.0-6.2 eV range induced in bulk amorphous SiO2 by beta-ray irradiation up to similar to 1 MGy at room temperature. The induced absorption was measured in situ both during irradiation and in the post irradiation time. Our data evidence E', center as the main defect induced by irradiation and the partial decay of their absorption band at about 5.8 eV after irradiation. A quantitative analysis of the time evolution of the induced absorption shows that the transmission recovery observed after irradiation is compatible with the reaction of radiation-induced defects with H-related (H-2, H2O) species diffusing in the amorphous matrix (10.1016/j.jnoncrysol.2009.01.042)
  DOI : 10.1016/j.jnoncrysol.2009.01.042
• Ultra stable oscillators dedicated for space applications: oscillator and quartz material behaviors vs radiation
  
  • Cibiel Gilles
  • Boizot Bruno
  • Boy Jean-Jacques
  • Carlotti Jean-Francois
  • Cambon Olivier
  • Devautour-Vinot Sabine
  • Candelier Vincent
  • Lamboley Jacques
  • Guibert Pierre
  • Largeteau Alain
  • Inguimbert Christophe
  • Piccheda Delphine
  , 2006, pp.814-822. (10.1109/freq.2006.275494)
  DOI : 10.1109/freq.2006.275494
• Ultra stable oscillators dedicated for space applications. Oscillators and quartz materials behavior vs radiations
  
  • Ciebiel G.
  • Boizot B.
  • Boy J.J.
  • Carlotti J.F.
  • Cambon Olivier
  • Devautour-Vinot Sabine
  • Candelier V.
  • Guibert Philippe
  • Largeteau Alain
  • Inguimbert C.
  • Piccheda D.
  • Lamboley J.
  Proceeding of the 2006 IEEE International Frequency Control Symposium, 2006, pp.814. This paper presents the first results obtained in the R&D studied initiated by the CNES at the end of 2004. Numerous french experts have been gathered to determine and to tentatively understand the mechanism responsible for the radiation sensitivity of quartz resonators and to correlate the results of various analyses in order to reduce or to anneal their susceptibilities.
• Paramagnetic defects induced by electron irradiation in barium hollandite ceramics for caesium storage
  
  • Aubin-Chevaldonnet V.
  • Gourier D.
  • Caurant D.
  • Esnouf S.
  • Charpentier T.
  • Costantini J.-M.
  Journal of Physics: Condensed Matter, IOP Publishing [1989-....], 2006, 18, pp.4007-4027. (10.1088/0953-8984/18/16/009)
  DOI : 10.1088/0953-8984/18/16/009
• Effects of temperature and flux on oxygen bubble formation in Li borosilicate glass under electron beam irradiation
  
  • Ollier N.
  • Rizza Giancarlo
  • Boizot Bruno
  • Petite Guillaume
  Journal of Applied Physics, American Institute of Physics, 2006, 99 (7), pp.073511. Oxygen bubble formation and evolution under a 300 keV electron beam are analyzed in a Li borosilicate glass under different irradiation conditions: temperature, flux, and dose. Oxygen bubbles are observed to form in a delimited flux and temperature region with a threshold requirement. This region ranges between 100 and 300 degrees C for the temperatures and between 10(19) and 10(21) e m(-2) s(-1) for the electron fluxes. In situ transmission electron microscopy allows the bubble evolution kinetics to be described as a four-step process. An incubation step is followed by a growth phase of sigmoid type. For high values of temperature and/or flux the saturation growth and the subsequent dissolution of the bubbles are also observed. The bubble evolution kinetics can be explained by considering the production and diffusion mechanisms of the molecular oxygen O-2 as a function of the temperature and the electron flux. (10.1063/1.2189026)
  DOI : 10.1063/1.2189026
• Bi-directional porous alumina wire templates for nanowire field-effect transistors
  
  • L. Wade Travis
  • Hoffer Xavier
  • Dayen Jean-François
  • Dughaim Mohammed Al
  • Humel Fahad
  • Wegrowe Jean-Eric
  Materials Research Society Symposia Proceedings, 2006, 901E, pp.Rb07-02.1. Using readily available materials and equipment we are able to sculpture aluminium wires into cylindrical, bi-directional templates for the synthesis and contacting of nanowires as field-effect transistors. The nanowire template is made by partial anodization of the wire perpendicular to its axis as an isolating layer for a gate electrode, vapour deposition of a metal on this layer as a gate, cutting the wire perpendicular to its axis, and finally anodizing the newly exposed area parallel to the wire axis as a template for nanowires. This results in a nanowire template surrounded by a gate electrode that is isolated from the template by the first anodisation layer. The utility of this structure is demonstrated by a ZnO nanowire field-effect transistor. The ZnO was made by electrodeposition of Zn nanowires in the interior nanoporous template during which an anodic pulse was applied to form a layer of ZnO in the middle of the zinc nanowires. The IV and transfer plots indicate that the ZnO is p-type in depletion mode. This 3-D transistor is unique in that it can be totally fabricated in a beaker without the need for costly clean room and lithography facilities. The ease and low cost of this new approach to nanodevices will have the effect of liberating nanoscience for scientists of moderate means. As a result this will open nanoscience to new ideas and more inputs.