Epitaxial YBa2Cu3O7-delta/SrTiO3 heterostructures grown on LaAlO3 substrate by pulsed laser deposition for voltage tunable microwave filter applications

The performance of microwave devices containing electrically tunable layers of strontium titanate has been evaluated for samples produced by pulsed la ser ablation over a range of deposition temperatures on (001) LaAlO3 substr ate. At zero bias the samples which exhibited the highest agility also exhi bited the highest loss. It has been observed that the SrTiO3 lattice parame ter is the relevant parameter in determining both the frequency agility of the sample and its dielectric loss. Furthermore, it was seen that whilst th e SrTiO3 lattice parameter is dependent on deposition temperature, it has a maximum, and that samples grown at higher/lower temperatures around this m aximum exhibit similar electrical properties for similar lattice parameter. A sample was then processed by a high temperature annealing of the SrTiO3 layer prior to YBCO deposition and it was found that dielectric loss is red uced over the whole range of agility without deterioration of the frequency agility.