Crystal structure and microwave resistance of YBa2Cu3O7−δ films prepared by cross-beam pulsed-laser deposition

Abstract

High-Tc superconducting YBa2Cu3O7−δ (YBCO) films were prepared by a unique pulsed-laser deposition using crossed-laser-beam technique onto LaAlO3 substrates in order to develop a basic technology for microwave-device application. The pulsed-laser deposition set-up uses two Nd–YAG lasers with 1064 nm wavelength and 0.3 J/pulse power. The unique feature of this method is a possibility to get a plasma plume with a low level of ‘droplet’, which essentially improves the film-surface quality. Transmission-electron microscopy and x-ray data show that YBCO films deposited at substrate temperature (Ts) of 780 °C exhibit a minimal density of dislocations in the crystal. YBCO films deposited at Ts = 780 °C with a cooling rate of V = 3 K min−1 have the smallest surface resistance below the transition temperature.