Characterization of dielectric properties of oxide materials in frequency range from GHz to THz

We measured complex dielectric permittivity using THz time-domain spectroscopy (THz-TDS) to clarify the dielectric properties of oxide materials in a frequency range from GHz to THz. Piezoelectric and ferromagnetic oxide single crystals, such as quartz (SiO₂), zinc oxide (ZnO), Bi substituted rear-earth iron garnet (BiRIG), and LiTaO₃ (LT), were used. We obtained the complex dielectric permittivity of these materials in a frequency range from 100 GHz to 2 THz. The ɛ′ and ɛ″ obtained for SiO₂ were in agreement with previous reports. We observed dielectric relaxation in ZnO crystal from 100 GHz to 1 THz, which originated from n-type conductivity. In the BiRIG, the values of the dielectric permittivity increased as the frequency increased, and the values of the dielectric permittivity with the magnetic field were smaller than those without the magnetic field throughout the measured frequency range. In a comparison between congruent LiTaO₃ (CLT) and stoichiometric LiTaO₃ (SLT), the ɛ₃₃ of the CLT was very similar to that of the SLT, but a lot of difference was between the ɛ₁₁ of evident CLT and SLT within the measured frequency region. We determined that the point defects had profound effect on the dielectric performance of the LT.