Measurements of Nonlinear Polarization Dynamics in the Tens of Gigahertz.

Frequency-dependent linear-permittivity measurements are commonplace in the literature, providing key insights into the structure of dielectric materials. These measurements describe a material's dynamic response to a small applied electric field. However, nonlinear dielectric materials are widely used for their responses to large applied fields, including switching in ferroelectric materials, and field tuning of the permittivity in paraelectric materials.

Targeted chemical pressure yields tuneable millimetre-wave dielectric.

Epitaxial strain can unlock enhanced properties in oxide materials, but restricts substrate choice and maximum film thickness, above which lattice relaxation and property degradation occur. Here we employ a chemical alternative to epitaxial strain by providing targeted chemical pressure, distinct from random doping, to induce a ferroelectric instability with the strategic introduction of barium into today's best millimetre-wave tuneable dielectric, the epitaxially strained 50-nm-thick n = 6 (SrTiO)SrO Ruddlesden-Popper dielectric grown on (110) DyScO. The defect mitigating nature of (SrTiO)SrO results in unprecedented low loss at frequencies up to 125 GHz.