Measuring the permittivity tensor of anisotropic DyScO3 to 110 GHz

DyScO3 (DSO) serves as a substrate on which to grow epitaxial thin films with extraordinary materials physics. The film properties are determined by the biaxial in-plane strain due to DyScO3's slight lattice mismatch in comparison to common perovskite films. Hence, DyScO3 is an attractive substrate for materials studies, yet its highly anisotropic permittivity makes some measurements exceedingly difficult. For instance, there are limited metrologies to characterize its permittivity at millimeter-wave frequencies that are suitable for the small lateral dimensions that DyScO3 can be grown in. To overcome this characterization gap, we tested an on-wafer method based on coplanar waveguides to measure the full anisotropic permittivity tensor from 0.1 to 110 GHz. We characterized two orthogonal sets of coplanar waveguides fabricated on each of two substrates with (001) and (110) crystallographic orientations to resolve the full permittivity tensor. To validate our measurements, we compared our results to data from dc parallel plate capacitors and THz time-domain spectroscopy. Our methodology closes the characterization gap in the complex permittivity of DyScO3 and, more generally, enables quantitative characterization of anisotropic dielectrics.