Fabrication of carrier controlled Y 1− xCa xBa 2Cu 3O 7− δ films on SrTiO 3( [formula omitted]) substrate by pulsed laser deposition

Abstract

Ca-doped ( x=0, 0.1, 0.2, and 0.3) Y 1− x Ca x Ba 2Cu 3O 7− δ films were fabricated on SrTiO 3 (1 0 0) substrate by pulsed laser deposition technique. The optimal deposition temperature and oxygen partial pressure were found to be 780°C and 400 mTorr, respectively. The films prepared in this manner exhibit excellent crystallinity and smooth surface morphology. The superconducting transition temperature ( T c) is found to decrease with increasing Ca content. The c-axis length was found to be insensitive with dopant concentration. We fabricated a series of samples by annealing at reduced oxygen pressures in order to study the dependence of carrier concentration on the oxygen deficiency, δ. The Ca content of those samples were 30% which is the solid solubility limit of Ca-doped YBa 2Cu 3O 7− δ . The increase of T c with increasing δ was attributed to the effect of overdoping. Although the films were overdoped, majority of the carriers supplied by Ca were found to be compensated by the creation of oxygen vacancies.