Electric response as a function of applied voltage of Nb-doped Bi4Ti3O12 thin films

We have investigated the electrical properties of sol-gel deposited Nb-doped Bi4Ti3O12 (NBIT) ferroelectric thin films. The obtained values of remanent polarization (2P(r)) and coercive voltage (V-c) were 7 mu C/cm(2) and 2.5 V of NBIT thin film, respectively. From complex dielectric spectra, we observed the dielectric response consisting of two regions for measuring frequency; the low frequency region may be due to diffusion charge transport caused by impurities, while the dielectric relaxation mechanism of high frequency region seems to be the modified Debye type. A model was proposed to account for the observed phenomena, which fits very well to the dielectric dispersion relation: epsilon* (omega) = epsilon(infinity) + epsilon(s) - epsilon(infinity)/1 + (i omega tau)(n) + i sigma/epsilon(0)omega. The occurrence of in n, sigma, tau, and epsilon(S) - epsilon(infinity) parameters near V-c indicates a coupling between the charge caniers and ferroelectncity. (C) 2007 Elsevier B.V. All rights reserved.