Electron-beam evaporated bismuth ferrite (BiFeO₃) thin films and characterization

The BiFeO₃ (BFO) thin films made by the electron beam evaporator are systematically investigated. As the most difficult part of this work, the preparation process is repeated until the optimal deposition power and elemental composition of BFO are obtained. With the help of X-ray diffraction and Raman spectroscopy, we specify precisely that the sample annealed at the temperature of 650 °C is the purest BFO phase with rhombohedral R3c structure. The Scanning Electron Microscopy images provide the surface morphology and cross-sectional thickness of each sample for the further performance analysis. With the aim of understanding the changes in the chemical bond structure of BFO samples at the different annealing temperatures, we applied X-ray photoelectron spectroscopy and the result indicates that the absorption of oxygen is increasing with the raising of the annealing temperature. Finally, we measured the magnetic property and resistivity of BFO samples to explore their applications. The saturation magnetization measurement shows the correlation between the magnetization of BFO and microstructures such as phase structure, grain size. Meanwhile, the electronic resistivity explains the close relationship between the resistivity and surface morphology. (paper)