Composite tapes of the superconductor Bi2Sr2CaCu2O8 on silver were irradiated with energetic light ions (0.8 GeV protons), creating extended splayed tracks ∼7 nm in diameter via fission of Bi nuclei. Magnetic hysteresis indicates large enhancements of persistent currents J, especially at high fields and temperatures, and substantial expansion of the irreversible regime. The technique may be suitable for large scale applications due to the long range (∼half meter) of fast protons.
Field emission data from aligned graphitic nanofibers have been obtained. The aligned nanofibers are 50–100 nm in diameter and 6–10 μm in length, with a density of 109–1010/cm2. The fibers were grown on polycrystalline nickel substrate by plasma-assisted hot filament chemical vapor deposition using a gas mixture of nitrogen and acetylene. The onset of emission current in microampere level was detected at about 1.8 V/μm with an emission area of 1 mm2. The Fowler–Nordheim model was used to analyze the data obtained. The field emission current required for flat panel display can be easily achieved at 2.5 V/μm.
Y-Ba-Cu-O thin films have been grown on silicon at a substrate temperature of 400 °C by plasma-assisted laser deposition technique. These films were superconducting in an as-deposited state. Films deposited directly on silicon and films with a MgO buffer layer differed in their superconducting properties. Films with a MgO layer showed higher critical temperatures (70 K) and higher critical currents (3×103 A/cm2 at 31 K) than films deposited directly on Si. Depth profiling by Auger and x-ray photoelectron spectroscopy has been employed to study the diffusion and structural variation near the interface.
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