The interface between a ferroelectric Fe3O4 thin film and a semiconducting 0.05-wt. % Nb:SrTiO3 substrate was investigated by ferroelectric, pyroelectric, capacitance, transport, and nonlinear dielectric microscopy measurements. Ferroelectric polarization measurements showed that the magnetite films are ferroelectric with an onset temperature that coincides with the Verwey transition at 120-K and that the ferroelectric domains can be reversed by applying an electric field, but only if the films are grown on nondoped SrTiO3 substrates. Pyroelectric measurements and scanning nonlinear dielectric microscopy showed that a polar state is also present in Pd/Fe3O4/Nb:SrTiO3 heterostructures but the polarization could not be switched by applying an electric field. It is shown that the inability to switch the polarity of magnetite films grown on semiconducting Nb:SrTiO3 substrates is caused by the presence of a Schottky barrier that forms at low temperature at the Fe3O4/Nb:SrTiO3 interface. Systematic capacitance measurements were used to extract the film and interface layer capacitances and construct a quantitatively accurate equivalent circuit model for the Fe3O4/Nb:SrTiO3 heterostructures.
ASJC Scopus subject areas
- Physics and Astronomy(all)