Oxygen-vacancy-related relaxation and scaling behaviors of Bi0.9La0.1Fe0.98Mg0.02O3 (La,Mg-codoped BiFeO3) ferroelectric thin film

TL;DR

This study investigates oxygen-vacancy-related dielectric relaxation in La,Mg-codoped BiFeO3 thin films, revealing distinct hopping mechanisms, activation energies, and temperature-independent relaxation time distributions through impedance spectroscopy.

Contribution

It provides new insights into the relaxation mechanisms and scaling behaviors of oxygen vacancies and electrons in BLFM thin films, highlighting their different hopping processes and temperature effects.

Findings

Oxygen vacancies and electrons coexist and contribute to dielectric response.

Distinct activation energies for electrons below and above 110°C.

Relaxation time distribution for oxygen vacancies is temperature independent.

Abstract

Oxygen-vacancies-related dielectric relaxation and scaling behaviors of Bi0.9La0.1Fe0.98Mg0.02O3 (BLFM) thin film have been investigated by temperature-dependent impedance spectroscopy from 40 oC up to 200 oC. We found that hopping electrons and single-charged oxygen vacancies (VO.) coexist in the BLFM thin film and make contribution to dielectric response of grain and grain boundary respectively. The activation energy for VO. is shown to be 0.94 eV in the whole temperature range investigated, whereas the distinct activation energies for electrons are 0.136 eV below 110oC and 0.239 eV above 110oC in association with hopping along the Fe2+- VO.-Fe3+ chain and hopping between Fe2+-Fe3+, respectively, indicating different hopping processes for electrons. Moreover, it has been found that hopping electrons is in form of long rang movement, while localized and long range movement of oxygen vacancies coexist in BLFM film. The Cole-Cole plots in modulus formalism show a poly-dispersive nature of relaxation for oxygen vacancies and a unique relaxation time for hopping electrons. The scaling behavior of modulus spectra further suggests that the distribution of relaxation times for oxygen vacancies is temperature independent.