Impedance spectroscopy of ferroelectrics: The domain wall pinning element

Abstract

We introduce an equivalent-circuit element based on the theory of interface pinning in random systems to analyze the contribution of domain wall motion below the coercive field to the impedance of a ferroelectric, as a function of amplitude [Formula: see text] and frequency [Formula: see text] of an applied ac electric field. We demonstrate our model on a bulk [Formula: see text] (PZT) reference sample and then investigate capacitor stacks, containing ferroelectric [Formula: see text]–[Formula: see text] (BCZT) thin films, epitaxially grown by pulsed laser deposition on Nb-doped [Formula: see text] single crystal substrates and covered with Au electrodes. Impedance spectra from [Formula: see text] Hz to 1 MHz were collected at different [Formula: see text]. Deconvolution of the spectra is achieved by fitting the measured impedance with an equivalent-circuit model of the capacitor stacks, and we extract for [Formula: see text] kV/cm, a frequency-dependent permittivity of [Formula: see text] for the BCZT films from the obtained fit parameters. From an extended Rayleigh analysis, we obtain a coupling strength of 0.187 cm/kV between dielectric nonlinearity and dielectric dispersion in the BCZT films and identify different domain-wall-motion regimes. Finally, we construct a schematic diagram of the different domain-wall-motion regimes and discuss the corresponding domain-wall dynamics. Our approach can be utilized to replace purely phenomenological constant phase elements (CPEs) in modeling the impedance response of ferroelectrics and extracting material properties.

Domain Wall Movement in Undoped Ferroelectric HfO2: A Rayleigh Analysis

“…30 An addition of frequency dispersion to the Rayleigh element due to the pinning of DW 31 was later provided by Becker et al and applied to epitaxial and polycrystalline ferroelectric 0.5(Ba 0.7 Ca 0.3 )TiO 3 −0.5Ba-(Zr 0.2 Ti 0.8 )O 3 (BCZT) films. 16,17 This study shows an RF-sputtering process for undoped ferroelectric HfO 2 on superconducting NbN electrodes. 32 Such a junction might be an attractive way to develop lowtemperature, low-power superconducting electronics.…”

“…64 Nevertheless studies by Becker et al have shown a reduction in the coupling factor of frequency dispersion and field dependence for epitaxial ferroelectric BCZT compared to polycrystalline BCZT films. 16,17 This may be explained by the interplay between domain size and grain size of the polycrystalline films. If the grains are smaller than the domains, the film is less responsive to an external electrical field than a system with large grains and small domains.…”

“…However, it must be mentioned that there is still no definite understanding of the movement of DW in the coupled pinning regime. 16,59 If the field is increased beyond E PS = 0.8 MV/cm, partial switching of the ferroelectric domains takes place. 16,30 ■…”

“…16,59 If the field is increased beyond E PS = 0.8 MV/cm, partial switching of the ferroelectric domains takes place. 16,30 ■…”

Ferroelectricity and resistive switching in BaTiO$_3$ thin films with liquid electrolyte top contact for bioelectronic devices

“…In addition, we note that there is every reason to believe that also a continous change in resistance (memrisitve behavior) could be achieved in the EFS device by altering the ferroelectric domain structure with subcoercive voltage pulses [40]. The impedance response of memristive EFS devices in intermediated resistance states can be investigated by domain wall pinning element modeling [41], which may help to improve device performance. EFS memristors -acting as artificial synapses -with ultra-low switching voltages may be utilized in the future for direct coupling to a biological neuron, resulting in the formation of a two-terminal neuron-ferroelectric junction.…”