Effect of La and Co-doping on microstructure and electrical properties of BiFeO3 thin films

Abstract

Adding both La3+ and Co3+ was used to tune the microstructure and electrical properties of BiFeO3 (BFO) thin films, and Bi1−x La x Fe0.90Co0.10O3 thin films were grown on the SrRuO3-buffered Pt-coated silicon substrates by a radio frequency sputtering. A polycrystalline structure with (110) orientation was shown in thin films, and their resistivity dramatically increases as the La3+ content increases. Their dielectric constant increases, and dielectric loss decreases with increasing La3+ content. In addition, their ferroelectric and fatigue properties were enhanced with rising La3+ content. The thin films with x = 0.03 have optimum electrical properties (e.g., remanent polarization 2P r ~ 175.6 μC/cm2, coercive field 2E c ~ 699.5 kV/mm, dielectric constant e r ~ 257 and tan δ ~ 0.038), together with a good fatigue behavior. The impendence analysis of the films was conducted to identify the defects type during conductivity, and both hopping electrons and single-charged oxygen vacancies are mainly responsible for the conduction of grain and grain boundaries regardless of La3+ content. As a result, the doping with both La3+ and Co3+ benefits the improvement in the electrical properties of BFO thin films.