Charged defects and their effects on electrical behavior in Bi1−xLaxFeO3 thin films

Ferroelectric and dielectric characteristics of Bi1−xLaxFeO3 thin films deposited on SrRuO3 as bottom electrode have been investigated. In accordance with the Rayleigh model, it is in principle established that La doping in BiFeO3 effectively reduces the concentration of charged defects and dielectric loss, although there is a slight deviation at the high level of La doping (x=0.2). This departure is attributed to the reversible bending movement of pinned 180° domain walls, which contributes to the dielectric permittivity nonlinearly without inducing loss. In addition, the competition between domain wall pinning and depinning is determined to be the dominant fatigue mechanism, as shown by the enhanced fatigue endurance at the high La-doping level, test frequency, and electrical field.