Impedance spectroscopy of bilayered bismuth ferrite thin films

Abstract

Bi0.90La0.10Fe0.85Zn0.15O 3/Bi0.90La0.10Fe0.95Zn 0.05O3 bilayers with different thickness ratios were deposited on Pt-coated silicon substrates by radio frequency sputtering. A polycrystalline structure with a random grain orientation is induced for all bilayers, owing to the introduction of the bottom Bi0.90La 0.10Fe0.95Zn0.05O3 layer with a random orientation. Impedance spectroscopy shows that oxygen vacancies dominate the dielectric relaxation and electrical conduction of these bilayers, and their dielectric relaxation process gradually endures a transition from a long-range relaxation, the coexistence of long-range and localized relaxation, to a localized relaxation with increasing thickness ratios of Bi 0.90La0.10Fe0.85Zn0.15O 3. Scaling behavior indicates that their dielectric relaxation and conduction mechanisms are independent of the measurement temperature. Different electrical conduction behavior in impedance determines the electrical properties of these bilayers. The bilayer with a higher thickness ratio of Bi 0.90La0.10Fe0.95Zn0.05O3 exhibits a higher remanent polarization owing to the involvement of a low defect concentration, as confirmed by the impedance spectroscopy and the dielectric behavior. © 2011 American Institute of Physics.