MU016- deposition methods of BiFeO3 thin films

Bismuth iron oxide (BiFeO3 or BFO) is a particularly interesting multiferroic perovskite with ferroelectric and antiferromagnetic transition temperatures significantly above room temperature. In this work, BiFeO3 films are synthesized by a chemical solution deposition (CSD) sol-gel process on platinized silicon substrates and by physical vapor deposition (PVD) through RF-sputtering on iridium-sapphire substrates. The crystallization behavior and phase assemblage of these films was examined by X-ray diffraction (XRD). Analysis of CSD-prepared films revealed that a 0.25 M solution with 5% excess bismuth annealed at 550 ??C in air produced polycrystalline films with the lowest occurrence of non-perovskite Bismuth iron oxide phases. For films made by PVD, the absence of oxygen during sputtering was found to enhance phase purity, and using a target with 7% excess bismuth allowed phase-pure films to be prepared at 600 ??C. Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) were used to investigate the microstructure of the BiFeO3 films. Porosity was found to be a significant problem in CSD-prepared films that were dried on a hotplate at 300 ??C before annealing. Lowering the temperature of this drying step or omitting it was found to decrease root-mean-square (rms) surface roughness. The microstructure of the sputtered films was found to be dense, uniform, and crack-free a surface roughness of to 16 nm for BiFeO3 sputtered at 600 ??C.