Minimizing surface roughness and characterizations of superconducting YBa2Cu3O7δ(YBCO) for use as a bottom metallic-oxide electrode in Au/(Bi,La)4Ti3O12/YBCO thin film capacitors

A multilayer consisting of ferroelectric Bi3.25La0.75Ti3O12 (BLT) and superconducting YBa2Cu3O7-δ (YBCO) was fabricated by the pulsed laser deposition method. YBCO is known to be metallic at room temperature and can be a candidate for use as a base electrode in a metalferroelectric-metal capacitor. Efforts to scale down the surface roughness of YBCO films were done in advance by alterations of the partial oxygen pressures. An average surface roughness of 2 nm was obtained for 200-mTorr-deposited films, which were oriented in the (00l)-direction and had a critical temperature of 83 K. Ferroelectric BLT films deposited on YBCO were found to favorably grow in the (h00)-direction and revealed a remnant polarization of 0.5 μC/cm2 and a coercive field of 20 kV/cm.