Tang Weihua

Optical and electrical characterization of (BiFeO 3 ) 25 /(La 0.7 Sr 0.3 MnO 3 ) 25 multilayered thin films

(001) oriented(BiFeO 3 ) 25 /(La 0.7 Sr 0.3 MnO 3 ) 25 multilayered thin films are fabricated on (001)SrTiO 3 substrate by rf-magnetron sputtering. UV-vis absorption spectrum analysis in a photon energy range of 1.2-6.4 eV is carried out, and the result shows that in a range of 1.3-2.1 eV the absorption is enhanced compared with that on SrTiO 3 substrate. And the optical band gap of BiFeO 3 is around 2.7 eV, which is in accordance with other reportsed results very well. Furthermore, the current-voltage curves are measured in a temperature range of 100-300 K, and the analyses according to several dielectric conduction models exhibite that the space-charge-limited conduction is dominated in the fabricated (BiFeO 3 ) 25 /(La 0.7 Sr 0.3 MnO 3 ) 25 multilayered thin films.

Possible high Al substitution in the Tl-Ba-Ca-Cu-O superconducting system

The Al substitution in the Tl-Ba-Ca-Cu-O superconducting system was studied. Up to 70% of Tl can be substituted by Al, without significant reduction of Tc. X-ray diffraction indicates partial Al substitution does not alter the crystal structure of the 2223 phase. Excessive Al formed Al-Cu alloy and unidentified phases, which gradually destroyed the superconductivity.