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 (2Pr) and coercive voltage (Vc) were 7 μC/cm2 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: ε⁎⁡(ω)=ε∞+εs−ε∞1+(iωτ)n+iσε0ω. The occurrence of an anomaly in n, σ, τ, and εS − ε∞ parameters near Vc indicates a coupling between the charge carriers and ferroelectricity.