Influence of Substrate Bias on the Structural and Dielectric Properties of Magnetron-Sputtered Ba_xSr_1-xTiO₃ Thin Films

The application of a substrate bias during rf magnetron sputtering alters the crystalline structure, grain morphology, lattice strain and composition of Ba_xSr_1-xTiO₃ thin films. As a result, the dielectric properties of Pt/Ba_xSr_1-xTiO₃/Pt parallel-plate capacitors change significantly. With increasing substrate bias we observe a clear shift of the ferroelectric to paraelectric phase transition towards higher temperature, an increase of the dielectric permittivity and tunability at room temperature, and a deterioration of the dielectric loss. To a large extent these changes correlate to a gradual increase of the tensile in-plane film strain with substrate bias and an abrupt change in film composition.