Spectroscopic ellipsometry studies of YBa2Cu3O7-δ deposited on SrTiO3

The dielectric function ε=ε1−iε2 of the YBa2Cu3O7−δ high-Tc superconducting films grown on (100) SrTiO3 (c-axis oriented) and (110) SrTiO3 (ab-oriented) substrate was measured by spectroscopic polarization modulation ellipsometry (SPME) and changes in film orientation were studied by comparing films of various thicknesses. The films deposited on SrTiO3 (100) substrates demonstrated an isotropic ε1 that changed with film thickness. It is observed that the decrease in the metallic dielectric behavior associated with the increase in the thickness of the films grown on (100) SrTiO3 substrates is mainly due to a change in the orientation of the films. The films deposited on SrTiO3 (110) showed anisotropic dielectric behavior when the plane of polarization is parallel and perpendicular to the c-axis of the film. These studies show that for this high-temperature superconductor with anisotropic dielectric behavior, SPME is a highly sensitive technique capable of measuring small changes in the film orientation.