Study of epitaxial YBa₂Cu₃O_x films

Abstract

In this report we present a systematic study of epitaxial YBa2Cu3Ox films laser ablated on Y-cut LiNbO3 substrates. X-ray diffraction pattern indicates that the c-axis is perpendicular to the substrate plane and the (110) direction of the film is parallel to the [11.0] of the substrate with two domains with the (110 as a mirror plane. Resistivity of the film shows a typical metallic behaviour in the normal state with a sharp transition at 92K. The effects of oxygen deficiency on the resistivity are also studied. Oxygen content is controlled by annealing the sample either in low oxygen pressure or in vacuum and estimated from the c-axis lattice parameter determined by X-ray diffraction. As oxygen is depleted gradually, the film resistivity shows metallic, semiconducting, and eventually insulating behaviors. Superconducting percolation phenomenon is observed for the semiconducting sample at low temperatures.