Highly reliable epitaxial YBaCuO thin-films using pressure-controlled magnetron sputtering method

The authors systematically investigated the effects of discharge gas pressure on in situ YBaCuO thin-film formation by RF magnetron sputtering and ensured the reliability of the epitaxial YBaCuO films by pressure control. The film (100-nm thick and no protection) showed no sign of degradation in its T_c value for ~3000 h. Under the controlled discharge gas pressure, the in situ epitaxial YBaCuO film had a T_c of 87 K. The c-axis lattice constants and the critical temperatures came very close to the bulk values as the pressure was rising to 1 torr. The plasma emission spectra showed a reduction in the Ar spectrum intensities relative to the oxygen component with increasing pressure. This observation suggests that the reduced mean free path of the gas atoms is responsible for the improved film crystallinity and superconductivity