Structural and optical properties of Bi₂VO_5.5 thin films deposited on silicon substrates

Ferroelectric Bi₂VO_5.5 (BVO) thin films have been successfully fabricated on p-type Si (100) substrates by sol-gel method. The microstructures and surface morphologies of BVO thin films were studied by X-ray diffraction and atomic force microscopy, respectively. Bi2VO5.5 thin films show c-preferred orientation, which indicates that the films match very well with the p-type Si substrate. Raman spectra measurements were carried out to study the lattice vibration modes of BVO thin films. Optical properties of the BVO were investigated due to their potential optical applications. And the optical properties of the BVO thin films have been studied by spectroscopic ellipsometric measurements in the wavelength from 400 nm to 1700 nm. The optical constant refractive index and extinction coefficient have been obtained. The resulting refractive index and extinction coefficient of BVO films show difference due to the different annealing process of the films, which implies the importance of the post annealing process. The increase of the refractive index could be understood by the higher density of the BVO films caused by the crystallization after annealing process. The Optical properties indicate that BVO films have potential applications in optical devices.