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Leakage current of Pt/(Ba0.7Sr0.3)TiO3 (BST)/YBa2Cu3O7-δ capacitors on a (001) SrTiO3 substrate was studied. By modeling a low-dielectric constant layer, a so-called dead layer, between the Pt/BST interface as a parasitic capacitor in series with the bulk layer capacitor, the leakage current of Pt/BST interface was well analyzed based on the modified Schottky emission equation. Furthermore, a two-step schematic energy band diagram is proposed to explain the carrier transport through the Pt/BST interface. [ABSTRACT FROM AUTHOR]

Complex conductivity of FeSe0.5Te0.5 superconducting films has been investigated using backward-wave-oscillator spectroscopy in the terahertz frequency range. The normal state conductivity corresponds well to the lowfrequency limit of a Drude metal. In the superconducting state, the real part of the complex conductivity is not completely suppressed, indicating the existence of a strongly anisotropic gap. Weak features in the conductivity are consistent with the superconducting gap value close to 12 cm-1(1.5 meV). The experimental results are discussed within the framework of a two-gap model based on the s± symmetry of the order parameter. [ABSTRACT FROM AUTHOR]