Electrostrictive resonances in (Ba0.7Sr0.3)TiO3 thin films at microwave frequencies

The bias-voltage-dependent permittivity of (Ba0.7Sr0.3)TiO3 (BST) thin films with thicknesses ranging from 100 to 250 nm is investigated in the frequency range from 500 MHz to 40 GHz by impedance spectroscopy of integrated BST capacitors. The dielectric spectra of the films exhibit resonance phenomena in the 4-7 GHz range when a bias field is applied. It is shown that the main controlling parameter of the resonance frequency is the film thickness. Calculations based on the strong electrostrictive activity of the BST films underline the assumption that the emission of plane acoustic waves is the underlying mechanism for this behavior. (C) 2004 American Institute of Physics