Study of Microwave Dielectric Properties of Perovskite Thin Films by Near-Field Microscopy

Abstract

Perovskite thin film materials possess good dielectric properties, which vary with applied voltage, and have thus been thoroughly investigated for applications as thin film tunable microwave devices. However, the tunability of the thin film materials derived from the frequency response of the thin film devices suffers from ambiguity in extracting the true dielectric response of the thin film materials in microwave frequency regime. To circumvent such a difficulty, we investigated the dielectric properties of perovskite thin films by using a novel scanning evanescent microwave microscopy (SEMM). To extract the dielectric parameters from original microwave frequency response signal of SEMM probe, we perform a 3-dimensional (3D) finite element simulation to model the frequency behavior of the SEMM microwave probe. Dielectric images of the thin films with submicron resolution can be obtained by using such a near-field technique, which correlates very well with the morphology of the films examined by atomic force microscopy. Moreover, the dielectric images of dielectric thin films were compared to those of ferroelectric thin films in order to discuss the related dielectric mechanism of the materials.

Uncertainties in the permittivity of thin films extracted from measurements with near field microwave microscopy calibrated by an image charge model

“…Degradation of the dielectric properties of barium strontium titanate (BST) ferroelectric films due to argon ion milling during patterning was shown in [5], together with a demonstration of the recovery of the properties after annealing. The lateral resolution of measurements of dielectric properties was shown to be of the order of tenths of a micron in [40], where sub-micron sized particulates within a ferroelectric film were imaged. A method for extracting the uniaxial anisotropy of the relative permittivity and loss tangent of BST ferroelectric films was described in [41].…”