STRUCTURE PROPERTY RELATIONSHIPS IN FERROELECTRIC THIN-FILMS FOR FREQUENCY AGILE MICROWAVE ELECTRONICS/

Ferroelectric thin films, deposited by pulsed laser deposition (PLD), are currently being used to develop a new class of tunable microwave c ircuits based on the electric field dependence of the dielectric const ant. Single phase, (100) oriented Ba0.5Sr0.5TiO3 (BST) films have been deposited onto (100) LaAlO3, SrTiO3, and MgO substrates. Interdigitat ed capacitors patterned on top of the ferroelectric film have been use d to measure the dielectric constant and dissipation factor of these f ilms as a function of DC bias and temperature at 1 MHz and as a functi on of DC bias and frequency (1 to 20 GHz) at room temperature. The die lectric properties of the ferroelectric film is sensitive to both the deposition and post processing conditions. Optical imaging of the ferr oelectric films using confocal scanning optical microscopy (CSOM) show s reproducible polarization fluctuations over sub-micrometer length sc ales for BST films deposited onto SrTiO3 which are not observed for fi lms deposited onto MgO. Dielectric loss in the ferroelectric film is r educed through a combination of post deposition processing and donor/a cceptor doping of the films. The lowest dielectric loss measured has b een tan delta = 0.01 - 0.005.