Epitaxial YBa2Cu3O7-δ/SrTiO3 heterostructures grown by pulsed laser deposition for voltage agile microwave filter applications

The performance of tunable microwave devices based on heteroepitaxial YBa2Cu3Ox/SrTiO3 films on (001) LaAlO3 substrate has been evaluated. It has been ascertained that 'out-of-plane' SrTiO3 lattice parameter is the relevant factor in determining both the agility and dielectric loss of the SrTiO3 layers. After high temperature annealing (1100 C, 1 atm O2), only SrTiO3 layers deposited under low oxygen pressure (∝10-5 Torr) show an appreciable reduction of the dielectric losses whilst maintaining high agility. Annealed samples exhibit voltage independent losses of ∝5.10-3 simultaneously with 55% dielectric agility at 6 GHz and 77 K. (orig.)