Papers by Keyword: Doping

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Authors: E.N. Popova, Vladimir V. Popov, E.P. Romanov, S.V. Sudareva, E.A. Dergunova, A.E. Vorobyova, A.K. Shikov, S.M. Balaev
Abstract: Multifilamentary bronze-processed Nb3Sn-based composites have been studied by the methods of TEM and SEM. Ti as a doping element required for an enhancement of superconducting characteristics, especially in high magnetic fields, was inserted either in a bronze matrix, or in Nb filaments of a composite. It has been found that Ti diffuses into the growing Nb3Sn layer in both cases, and affects positively its structure and superconducting characteristics of a composite as a whole, especially in case of the doped matrix. When Ti is added to Nb filaments, it forms fine particles of intermetallic compounds with Sn in the nanocrystalline diffusion layer. When these particles are formed, grain boundaries of the diffusion Nb3Sn layer purify from segregations, and grains in the vicinity of these particles coarsen, which negatively affects the current-carrying capacity of a composite. That’s why an optimal amount of Ti in Nb should be chosen, when Ti mainly dissolves in the Nb3Sn phase increasing its superconducting properties and not deteriorating its grain structure.
Authors: A.V. Bolotnikov, Peter G. Muzykov, Anant K. Agarwal, Qing Chun Jon Zhang, Tangali S. Sudarshan
Abstract: In this work the analysis of thermal diffusion of boron carried out from vapor phase was performed. Two-branch diffusion associated with kick-out and substitution mechanisms was observed. The activation energy and prefactor were calculated from Arrhenius plot for each diffusion branch. It has been established that the surface layer of diffused boron mostly consists of shallow boron acceptors, while the tail of the diffusion profile has mostly deep level D centers.
Authors: Tetsuya Miyazawa, Takeshi Tawara, Hidekazu Tsuchida
Abstract: Epitaxial growth of 4H-SiC with intentional V or Ti doping was performed to obtain short minority carrier lifetimes, using VCl4 or TiCl4 as the doping sources. The doping efficiencies and quality of the epilayers were compared for H2+SiH4+C3H8 and H2+SiH4+C3H8+HCl gas systems. The addition of V or Ti in highly N-doped epilayer demonstrated very short minority carrier lifetimes of 20-30 ns at 250°C.
Authors: Omed Ghareb Abdullah, Sarkawt Abubakr Hussen
Abstract: Polymer composite of polyvinyl alcohol (PVA), Aluminum Iodide have been prepared by solution cast method for different doping concentrations. The absorption of pure and doped films have been investigated in the visible and ultraviolent wavelength regions. It was found that the optical absorption is due to direct and indirect transitions, and the optical energy gaps values shifted to lower energies on Aluminum Iodide doping concentration for all transitions, while the band edge width of the tail localized states increase with increasing Aluminum Iodide concentration. The band gap of all films shows to be decrease after thermal treatment. The optical constants refractive index n, extinction coefficient k, the complex dielectric constant have been also calculated. The dielectric constant increased in the composite samples as compared with the pure PVA sample prepared by the same method.
Authors: Harun Mindivan, H.I. Bakan, H. Çimenoğlu, E.S. Kayali
Authors: N. Boulares, K. Guergouri, Nouar Tabet, A. Lusson, F. Sibieude, Claude J.A. Monty
Abstract: ZnO oxide is a promising material for optoelectronics because of its wide and direct gap (Eg=3.4 eV). Pure and doped zinc oxide powders of various grain sizes have been synthesized by vaporisation-condensation method using a solar furnace. The initial powders contained from 0 to 5 In2O3 mol % . X-ray diffraction technique (XRD) has been used to measure the lattice parameter and the grain size as a function of the composition, the results show the appearance of the spinel phase Zn5In2O8 in the micopowders and the decrease of the grain size of nanopowders as the In concentration increases for all considered compositions. The photoluminescence spectra revealed the presence of two main transitions at 3.31 and 3.36 eV, a shift of the excitonic peaks towards the lower energies, a drastic reduction of the exciton bound to donor emission from the doped material and a large broadening of the excitonic emission in In doped nanopowder.
Authors: Yang Yang, Xiao Hui Wang, Long Tu Li
Abstract: Zinc-doped TiO2 nanotube arrays were fabricated by immersing TiO2 nanotube arrays in zinc-containing solution for hours. And subsequent heat-treatment was crucial for Zn2+ coming into the crystal lattice of TiO2 nanotubes. TEM analysis was used as main technique to investigate the structure of zinc-doped TiO2 nanotubes, and found that the Zn2+ ions only combine into the lattice of TiO2 nanotubes. This kind of doping can change the valence structure in the surface of TiO2 nanotube array. The obtained zinc-doped TiO2 nanotube arrays have potential application in photocatalysis.
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