Bismuth composition dependence of properties of Bi_xFeO₃ thin films

The Bi_xFeO₃ films (0.80≤x≤1.20) were prepared by sol-gel technique on Si substrates. Effects of x variation on microstructures and optical properties of the Bi_xFeO₃ films are reported. It is shown that in the films with both insufficient and excess bismuth dosage, impurity phases such as Bi₂Fe₄O₉ and iron oxide appeared. Raman spectra of the films were presented in the spectral range of 50~800 cm^-1. The refractive index (n) of the films decreases with increasing x at wavelength lower than 600 nm, the extinction coefficients (k) of all films were comparable. The bandgaps of the films changed from 2.65 eV to 2.76 eV.