Optical properties of BiFeO₃ and Bi_0.9La _0.1 FeO₃ films on silicon substrates

BiFeO₃ (BFO) and Bi_0.9La_0.1FeO₃ (BLFO) thin films were deposited on Si (100) wafer by sol-gel technique. The microstructure and surface morphology of the films were characterized using X-ray diffraction and atomic force microscope. After annealing at 600°C, all the films were well-crystallized, and the diffraction peaks corresponded to BFO standard pattern quite well. The optical properties of BFO and BLFO film were studied by spectroscopic ellipsometry in the wavelength range 420 to1700 nm. Compared with the BFO film, the BLFO film has lower refraction index and higher extinction coefficient in the wavelength range 600 to 1700 nm. The absorption coefficient of the BLFO film is greater than 1700cm^-1 in total measured wavelength region. The results suggest that the potential role of La dopant improved the optical properties of BFO thin film and the BLFO film is a promising material for photovoltaic devices.