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تسجيل مستخدم جديدSynthesis and Properties of c-axis Oriented Epitaxial MgB2 Thin Films
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S. D. Bu
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We report the growth and properties of epitaxial MgB2 thin films on (0001) Al2O3 substrates. The MgB2 thin films were prepared by depositing boron films via RF magnetron sputtering, followed by a post-deposition anneal at 850C in magnesium vapor. X-ray diffraction and cross-sectional TEM reveal that the epitaxial MgB2 films are oriented with their c-axis normal to the (0001) Al2O3 substrate and a 30 degree rotation in the ab-plane with respect to the substrate. The critical temperature was found to be 35 K and the anisotropy ratio, Hc2(parallel to the film) / Hc2(pendicular to the film), about 3 at 25K. The critical current densities at 4.2 K and 20 K (at 1 T perpendicular magnetic field) are 5x10E6 A/cm2 and 1x10E6 A/cm2, respectively. The controlled growth of epitaxial MgB2 thin films opens a new avenue in both understanding superconductivity in MgB2 and technological applications.
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The anisotropy of MgB2 is still under debate: its value, strongly dependent on the sample and on the measuring method, ranges between 1.2 and 13. In this work we present our results on a MgB2 c-oriented superconducting thin film. To evaluate the anis
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We have studied structural and superconducting properties of MgB2 thin films doped with carbon during the hybrid physical-chemical vapor deposition process. A carbon-containing metalorganic precursor bis(cyclopentadienyl)magnesium was added to the ca
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Temperature dependent optical conductivities and DC resistivity of c-axis oriented superconducting (Tc = 39.6 K) MgB2 films (~ 450 nm) have been measured. The normal state ab-plane optical conductivities can be described by the Drude model with a tem
perature independent Drude plasma frequency of omega_{p,D}=13,600 +/- 100 cm-1 or 1.68 +/- 0.01 eV. The normal state resistivity is fitted by the Bloch-Gruneisen formula with an electron-phonon coupling constant lambda_{tr} = 0.13 +/- 0.02. The optical conductivity spectra below T_c of these films suggest that MgB2 is a multi-gap superconductor.
We report on the transport, magnetization, and scanning tunneling spectroscopy measurements on c-axis oriented thin films of MgB2 irradiated with high energy heavy ions of uranium and gold. We find a slight shift in the irreversibility and upper crit
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We have studied the effect of deposition rate and layer thickness on the properties of epitaxial MgB2 thin films grown by hybrid physical-chemical vapor deposition on 4H-SiC substrates. The MgB2 film deposition rate depends linearly on the concentrat
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