Dielectric relaxation and electrical conductivity of random oriented BiFeO3 thin films

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Abstract
08-149 Eudes Borges Araújo Araújo, E.B.(São Paulo State University); Masteghin, J.F.(São Paulo State University); Reis, S.P.(São Paulo State University); The BiFeO3 (BFO) is a multiferroic material known by a room-temperature magnetization, a high Curie temperature (TC = 1103 K) and by ferroelectric properties with a giant remanent polarization. Despite potential technological applications for this multiferroic, the practical applications of the BFO thin films are still limited due to their large leakage current at room temperature. Alternatives to solve this and other problems of BFO thin films have been stimulated investigations on this system. In the present work, we report studies on the structural and electrical properties of BiFeO3 thin films deposited on Pt/TiO2/SiO2/Si(100) substrates by chemical solution route. The studied films were crystallized in O2 atmosphere at 600°C for 30 min and had thicknesses ~ 430 nm. Atomic force microscopy images show a dense and uniform topography with grain sizes around 280 nm in average. AC conductivity and modulus properties of BFO film were characterized through real (e') and imaginary (e'') dielectric permittivity measurements. Frequency, temperature and dc electric field dependence of these properties were studied in the ranges of 100 Hz to 1 MHz, 300 to 480 K and 0 to 84 kV/cm, respectively. Modulus analyses at different temperatures and frequencies reveal a dielectric relaxation and conduction mechanism similar to other results in the literature for BFO films prepared by different techniques. Measurement as a function of dc electric field within the same frequency range revealed a similar dielectric relaxation like observed as a function of the temperature. Both dielectric relaxation and conduction mechanisms are discussed in terms of intrinsic defects and interfacial polarization. The electric field shows a similar temperature effect on the ac conductivity. The conduction mechanism in BFO film is discussed based on data from Arrhenius plot.
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