Real and imaginary permittivity measured by thermal noise dielectric spectroscopy

Abstract

This paper demonstrates that both real and imaginary parts of dielectric permittivity in a kHz frequency range can be determined from the thermal noise voltage spectra. The proposed method, termed as thermal noise dielectric spectroscopy, relies on the set of calibration measurements of gauge resistors and capacitors. This method has a great potential for investigations of strongly nonlinear dielectric materials whenever the initial permittivity is of interest because the thermal noise method probes the permittivity by an almost zero electric field. Here, we tested this method by measuring dielectric spectra of 100 nm thin film of paraelectric SrTiO3 in a thermal noise setup in which the film is effectively probed by voltages of the order of nanovolts. For the sake of comparison, the permittivity of the same SrTiO3 thin film has been also measured using the standard impedance analyzer with the probing AC voltage of 10 mV. Agreement between methods is remarkable for both real and imaginary parts of the permittivity. Results strongly suggest that the proposed technique is broadly applicable for investigation of the frequency and temperature dependence of the complex permittivity of nanoscale dielectric materials.