Measurement of ionic polarization of SrTiO3 single crystal by far-infrared spectroscopic ellipsometry

Abstract

We developed a far-infrared spectroscopic ellipsometer for measuring the complex permittivity of high-permittivity materials in the terahertz (THz) region and demonstrated the dielectric function of SrTiO3 single crystal at 0.75–21 THz. The responses of the Slater, Last, and O6 displacive modes, which are all optical phonon modes of SrTiO3 at room temperature, were clearly observed. The complex permittivity measured by the ellipsometer agreed with the permittivity simulated by a damped harmonic oscillator model. The far-infrared spectroscopic ellipsometry is useful to analyze the phonon modes of high-permittivity materials, which enable us to understand the contribution of the ionic polarizations to the low-frequency permittivity.

Usage of P–V–L bond theory in studying the structural/property regulation of microwave dielectric ceramics: a review

“…Up to now, several theories have been developed to study the regulation between crystal structure and dielectric pro-perties. For example, THz time-domain spectroscopy and farinfrared reflectance spectroscopy can be used to analyse the intrinsic properties of the lattice vibration of material systems; [28][29][30][31] the Clausius-Mossotti equation predicts the macroscopic dielectric constant of an ionic crystal by using ionic polarizabilities; 32,33 bond-valence theory gives the actual valence state of ions in a crystal structure and provides the basis for the state of the ions. [34][35][36][37] These concepts help researchers gain better insights into the relationship between crystal structure and dielectric properties.…”

Terahertz ellipsometry study of the soft mode behavior in ultrathin SrTiO3 films

“…We show in the following that the combination of continuous wave Fourier-transform (FTIR) ellipsometry in the far infrared range [20][21][22] with time-domain terahertz (TD-THz) ellipsometry [19,[23][24][25][26] enables one to study the temperature evolution of the STO soft mode in thin (82 nm) and even ultrathin (8.5 nm) films and to obtain experimental quantities that can be directly interpreted in terms of the optical conductivity of the film.…”

Broadband Terahertz Spectroscopy of Phonon-Polariton Dispersion in Ferroelectrics

“…Therefore, the study of the 3T 1u modes is possible using infrared spectroscopy, including THz-TDS and hyper-Raman scattering. The lowest-frequency T 1u modes have been studied using far-IR spectroscopy [29] and THz-TDS [30][31][32].…”