High frequency dielectric properties distribution of BiFeO3 thin film using near-field microwave microscopy

A near-field scanning microwave microscopy (NSMM) is. applied to investigate the local perpendicular dielectric information of single-phase multiferroic BiFeO3 thin film and single crystal LaAlO3 material. Our NSMM is composed of a vector network analyzer and a simple open-ended coaxial probe, which is quite different from the commercial probe with a lambda/4 coaxial resonator. The local permittivity is calculated quantitatively according to resonance frequency shift under the quasistatic microwave perturbation theory. We make use of the magnitude of reflection loss S-11 to construct an image reflecting the distribution of dielectric constant of a material. A homogeneous permittivity is observed in LaAlO3 material and the inhomogeneous permittivity epsilon=215-250 for BiFeO3 film is depicted from the change of feedback signal S-11 over an area of 100 x 100 mu m(2). (C) 2009 American Institute of Physics. [doi:10.1063/1.3258201]