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

Abstract

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 λ/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 S11 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 ε=215-250 for BiFeO3 film is depicted from the change of feedback signal S11 over an area of 100×100 μ m2. © 2009 American Institute of Physics.