Enhanced dielectric properties of SrTiO3 epitaxial thin film for tunable microwave devices

The performance of tunable microwave devices based on heteroepitaxial YBa2Cu3Ox/SrTiO3 films on (001) LaAlO3 substrates has been evaluated. It was ascertained that “out-of-plane” SrTiO3 lattice parameter is the relevant factor in determining both device agility and dielectric loss. 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 while maintaining high agility. Annealed samples exhibit voltage independent losses of ∼5×10−3 simultaneously with 55% dielectric agility at 6 GHz and 77 K.