FABRICATION AND CHARACTERIZATION OF BA1-XSR1-XTIO3 TUNABLE THIN-FILM CAPACITORS

Polycrystalline Ba1-xSrxTiO3(x=0.9) thin films have been successfully prepared from sintered stoichiometric ceramic targets by means of the 90 degrees off-axis r.f. sputtering technique at substrate temperature s from 500 to 600 degrees C. Films grown on lanthanum aluminate(100) a t 550 degrees C are predominantly c-axis oriented. Those deposited on sapphire(1 $($) over bar$$ 102) did not reveal any preferred growth or ientation. Dielectric measurements were performed using planar capacit or geometries. The dielectric constant of these films showed a broad f erroelectric-to-paraelectric transition at 50 to 70 K, depending on th e thickness of the films. The dielectric constant of these films also showed a small electric field dependence, changing by 5% at 77 K and a t a field strength of 20kVcm(-1). The results are compared with those obtained from bulk samples, and are interpreted in the framework of ph enomenological theory.