Anisotropic properties of La8-xSrxCu8O20-δ epitaxial thin films (JP)

La8-xSrxCu8O20-δ thin films are epitaxially grown on SrTiO3 single-crystal substrates by rf magnetron sputtering. They exhibit anisotropic electrical and optical properties in directions from parallel to perpendicular to the c axis, but the degree of anisotropy is smaller than that found in the usual high-Tc superconductors. The resistivity in the [001] direction is metallic and that in the [100] direction exhibits a broad peak at about 180 K. The anisotropic behavior can be explained by assuming that this matter has a quasi-one-dimensional electronic structure. Furthermore, the Hall coefficients are negative and decrease rapidly with decreasing temperature. The plasma frequency ωp is about 1.3 eV and this value is near that of Ba(Pb,Bi)O3