Deposition and characterization of low-loss epitaxial non-linear dielectric thin films for microwave devices

Oxide ferroelectric thin films for frequency-tunable microwave devices, in which the dielectric constant of the non-linear dielectric is varied by application of electric fields, have been deposited using PLD. We have fabricated single phase epitaxial Ba0.6Sr0.4TiO3 and KTaO3 thin film capacitors for applications at 300K and 77K, respectively. Single phase KTaO3 films were obtained only with excess potassium source in the target along with KTaO3 perovskite phase. The films have been characterized for structure and morphology by X-ray diffraction and AFM. The dielectric properties were measured in the low frequency range from 100 kHz to 10 MHz, using interdigitated capacitors. Low loss tangents (0.002 at 300K) were observed for highly oriented Ba0.6Sr0.4TiO3 films. The importance of low losses for various devices is discussed and the dielectric constants, loss tangents and tunability of these films are reported in this paper.