An electrode-free method of characterizing the microwave dielectric properties of high-permittivity thin films

Abstract

A thin dielectric resonator consisting of a dielectric substrate and the thin film deposited upon it is shown to suffice for microwave characterization and dielectric parameter measurement of high-permittivity thin films without electrodes. The TE01δ resonance mode was excited and measured in thin (down to 0.1 mm) rectangular- or disk-shaped low-loss dielectric substrates (D∼10 mm) with permittivity ε′≥10 inserted into a cylindrical shielding cavity or rectangular waveguide. The in-plane dielectric permittivity and losses of alumina, DyScO3, SmScO3, and (LaAlO3)0.29(SrAl1/2Ta1/2O3)0.71 (LSAT) substrates were measured from 10 to 18 GHz. The substrate thickness optimal for characterization of the overlying thin film was determined as a function of the substrate permittivity. The high sensitivity and efficiency of the method, i.e., of a thin dielectric resonator to the dielectric parameters of an overlying film, was demonstrated by characterizing ultrathin strained EuTiO3 films. A 22 nm thick EuTiO3 film grown on a (100) LSAT substrate and strained in biaxial compression by 0.9% exhibited an increase in microwave permittivity at low temperatures consistent with it being an incipient ferroelectric; no strain-induced ferroelectric phase transition was seen. In contrast, a 100 nm thick EuTiO3 film grown on a (110) DyScO3 substrate and strained in biaxial tension by 1% showed two peaks as a function of temperature in microwave permittivity and loss. These peaks correspond to a strain-induced ferroelectric phase transition near 250 K and to domain wall motion.

Microwave dielectric measurement methods on the base of the composite dielectric resonator

“…Measurement of microwave properties of materials is a complex task and requires high-precision measuring equipment [1,2,3,4].…”

Spin-phonon coupling in epitaxialSr0.6Ba0.4MnO3thin films

“…If we take into account the very small thickness of the films (13 nm) with respect to that of the substrates (480 μm) and an uncertainty of the substrate thickness at the micrometer level together with a limited precision of the thin film parameters calculation procedure [15], one can understand that absolute values of the MW ε * μ * film parameters are only a rough estimation. Nevertheless, the thin dielectric resonator method provides very high sensitivity to the relative changes of the ε * μ * film parameters with temperature [15].…”

“…Nevertheless, the thin dielectric resonator method provides very high sensitivity to the relative changes of the ε * μ * film parameters with temperature [15]. Therefore we consider temperature changes of the real Re(ε * μ * ) and imaginary Im(ε * μ * ) parts of the film complex electromagnetic response as reliable characteristics and use them for indication of possible phase transitions of both magnetic and ferroelectric nature.…”

“…More details about evaluation of the two-layer optical system (substrate and semitransparent thin film) can be found elsewhere [12,14]. For MW characterization of the films, an electrodeless thin dielectric resonator method was used [15]. The TE 01δ resonance modes were excited in the substrates with and without film in the shielding cavity.…”

Unusual ferroelectric and magnetic phases in multiferroic 2H−BaMnO3 ceramics

“…For microwave dielectric measurements, the method of a composite dielectric resonator 37,38 was used. TE 01δ resonance modes were excited first in the base cylindrical dielectric resonator and then in the composite dielectric resonator, consisting of the base and the sample in the shielding cavity.…”