Dielectric characterization in a broad frequency and temperature range of SrBi2Nb2O9 thin films grown on Pt electrodes -: art. no. 114102

Ferroelectric and dielectric characteristics of two types of SrBi2Nb2O9 thin films grown by pulsed laser deposition on Pt electrodes were determined: a randomly oriented SrBi2Nb2O9 film (sample A), grown on a so-called polycrystalline Pt/Ti/SiO2/Si (Pt/Si) and an epitaxial SrBi2Nb2O9 film (sample B) grown on a (110)Pt electrode epitaxially grown on (110)SrTiO3. Some h00 texturation was suggested by the strong intensity of the 200 diffraction peak in sample A whereas the epitaxial sample B presents a strongly (116) preferential orientation as evidenced by x-ray diffraction and electron channeling patterns. Remanent polarization (P-r) determined from the hysteresis loops recorded on several electrodes on samples A and B was typically in the range of 5-8.5 mu C/cm(2) for both samples. The Curie temperature (T-C) determined from dielectric permittivity measurements versus temperature was 705 K, for both samples, which differ, in fact, in structural characteristics but not in composition. The Curie-Weiss temperature was found lower than T-C, suggesting that the transition is of first order. The evolution of dielectric permittivity and dissipation factor was recorded versus frequency at different temperatures. At room temperature and low frequency (100 Hz), epsilon(') is close to 150 on both films. When increasing the frequency up to 1 MHz, the epsilon(') value decreased down to 137 for sample A and 129 for sample B. This evolution corresponds to a weak dispersion effect in relation with the high crystallization quality of the ferroelectric films. At the same time, dissipation factor tg delta increased from 1.5% to 1.8% and from 3.3% to 5.5% for samples A and B, respectively, when increasing the frequency from 100 Hz to 1 MHz. Further measurements at higher frequency were performed on the epitaxial film. As expected, dielectric permittivity decreased to about 100 when increasing the frequency to 0.5 GHz at room temperature, whereas tg delta increased up to about 9%. Decreasing the temperature down to 110 K contributes to decrease epsilon(') from 150 at room temperature to 122 at 110 K at 1 kHz and from 100 to 87 at 0.5 GHz. Simultaneously, tg delta decreases from 8.7% to 5.6% at 0.5 GHz. (C) 2005 American Institute of Physics.