Dynamic tuning of dielectric permittivity in BaTiO<inf>3</inf> via electrical biasing

Dynamic tuning of optical properties is technologically important for the development of future integrated electronic and photonic devices. Here, we demonstrate the electrically tunable permittivity in optical frequency in epitaxial BaTiO3 (BTO) thin films using spectroscopic ellipsometer measurements under DC bias condition. The lattice tetragonal distortion and domain switching of biased BTO is evident based on the increased anisotropy in permittivity in-plane and out-of-plane. Specifically, out-of-plane permittivity, arising from the c-domains, shows a continuous decrease with the applied voltage, relative to the in-plane permittivity, arising from the a-domains. The dielectric constant can also be reversibly adjusted through electric-reset cycles.