THE DIELECTRIC RESPONSE AS A FUNCTION OF TEMPERATURE AND FILM THICKNESS OF FIBER-TEXTURED (BA,SR)TIO3 THIN-FILMS GROWN BY CHEMICAL-VAPOR-DEPOSITION

The temperature-and field-dependent permittivities of fiber-textured B a0.7Sr0.3TiO3 thin films grown by liquid-source metalorganic chemical vapor deposition were investigated as a function of film thickness. Th ese films display a nonlinear dielectric response under conditions rep resentative of those encountered in dynamic random access memories or other integrated capacitor applications. This behavior has the exact f orm expected fora classical nonlinear, nonhysteretic dielectric, as de scribed in terms of a power series expansion of the free energy in the polarization as in the Landau-Ginzburg-Devonshire approach. Curie-Wei ss-like behavior is exhibited above the bulk Curie point (similar to 3 00 K), although the ferroelectric phase transition appears frustrated. Small-signal capacitance measurements of films with different thickne sses (24-160 nm) indicate that only the first term in the power series expansion varies significantly with film thickness or temperature. Po ssible origins for this thickness dependence are discussed. (C) 1997 A merican Institute of Physics.