996 resultados para Electron-phonon


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In the above entitled paper (ibid., vol. 55, no. 11, pp. 3001-3011), two errors were noticed after the paper went to press. The errors are corrected here.

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The aim of this paper is to describe the growth and optimization of carbon nanotube (CNT) and CNT/Zinc Oxide nanostructures to produce novel electron sources. The emitters studied in this project are based on regular array of vertically aligned 5 μm height and 50 nm diameter CNTs with a pitch of 10 μm as described previously (1). Such a cathode design allows us to minimize electric field shielding effects and thus to help in optimizing the emitted current density. We have previously obtained a current density of 1 A/cm 2 from such arrays in DC mode, and over 12 A/cm2 in pulsed mode at RF frequencies. © 2010 IEEE.

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Thin films of nano-composite Y-Ba-Cu-O (YBCO) superconductors containing nano-sized, non-superconducting particles of Y2Ba 4CuMOx (M-2411 with M = Ag and Nb) have been prepared by the PLD technique. Electron backscatter diffraction (EBSD) has been used to analyze the crystallographic orientation of nano-particles embedded in the film microstructure. The superconducting YBa2Cu3O7 (Y-123) phase matrix is textured with a dominant (001) orientation for all samples, whereas the M-2411 phase exhibits a random orientation. Angular critical current measurements at various temperature (T) and applied magnetic field (B) have been performed on thin films containing different concentration of the M-2411 second phase. An increase in critical current density J c at T < 77 K and B < 6 T is observed for samples with low concentration of the second phase (2 mol % M-2411). Films containing 5 mol % Ag-2411 exhibit lower Jc than pure Y-123 thin films at all fields and temperatures. Samples with 5 mol % Nb-2411 show higher Jc(B) than phase pure Y-123 thin films for T < 77 K. © 2010 IOP Publishing Ltd.

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We characterized the electrical conductance of well-structured multi-walled carbon nanotubes (MWCNTs) which had post-treated by a rapid vacuum arc thermal annealing process and structure defects in these nanotubes are removed. We found that the after rapid vacuum arc annealing, the conductivity of well-structured MWCNTs can be improved by an order of magnitude. We also investigated the conductivity of MWCNTs bundle by the variation of temperatures. These results show that the conductance of annealed defect-free MWCNTs is sensitive to temperature imply the phonon scatting dominated the electron conductions. Compare to the well-structured MWCNTs, the defect scattering dominated the electron conduction in the as-grown control sample which has large amount of structure defects. A detail measurement of electron conduction from an individual well-structured MWCNT shows that the conductivity increases with temperatures which imply such MWCNTs exhibited semiconductor properties. We also produced back-gated field-effect transistors using these MWCNTs. It shows that the well-structured MWCNT can act as p-type semiconductor. © 2010 IEEE.

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The aim of this paper is to describe the growth and optimization of ballasted carbon nanotube (CNT) and CNT/Zinc Oxide nanostructures to produce novel electron sources for use in lighting and x-ray applications. © 2010 ITE and SID.