Abstract
Multiferroics BiFeO3 (BFO), exhibiting simultaneously ferroelectricity (Tc~1100K) and anti-ferromagnetism (TN~640K), have attracted extensively attention for their coupled electric, magnetic, and structure order parameters in the same phase. The crystal structure, chemical configuration, nanoscale characterization, electric and magnetic properties were investigated is this study. The pure perovskite phase of BFO films were deposited by rf-magnetron sputtering at low processing temperature. The crystal structure of the BFO films was significantly influenced by the substrate and the bottom electrodes. The BFO film was grown with random orientation on Pt/TiOx/SiO2/Si (Pt), whereas highly (100)- and (111)-oriented ones were obtained on LaNiO3/Pt/TiOx/SiO2/Si (LNO) and BaPbO3/Pt/TiOx/SiO2/Si (BPO), respectively. The BFO-based films were hetero-epitaxially grown on the LaNiO3/LaFeO/MgO single crystal substrates.The chemical configuration of the films, which significantly depended on working pressure and temperature, was enhanced by well-controlled processing parameters. The orientation dependence in the crystal growth, electric properties and magnetic behavior of BFO films were examined. The film/electrode interface and chemical homogeneity of the films were characterized by the scanning transmission electron microscope high-angle annular dark-field imaging (STEM-HAADF). Nanoscale characterization of the BFO films was studied by scanning probe microscopy (SPM). With the partial substitution of lanthanum (La) ions for bismuth ions, the significant enhancement in the dielectric, ferroelectric and magnetic performance of BFO films was attributed to the improved crystallinity, smooth surface, and increased lattice volume.