Tunable TTB strontium and tantalum based thin films: Influence of the deposition parameters on the structural and dielectric properties

Structural and dielectric properties of thin films produced by reactive radiofrequency sputtering of a (Sr2Ta2O7)(100-x) (La2Ti2O7)(x) target with x = 1.65 were studied. The chemical composition characterization shows Sr/Ta ratios ranging between 0.49 and 0.56, thus pointing out the deposition of strontium deficient films, belonging to the tetragonal tungsten bronze family. The highest permittivities and tunabilities, associated with the lowest dielectric losses, are obtained when films are pure and fully textured. This is achieved for a 900 nmthick film deposited at T-s = 850 degrees C: epsilon' = 116, tan delta = 0.007 and tunability T = 14.5% at 340 kV/cm and 100 kHz.