Composition dependence of optical constants in ferroelectric Ba(Ti 1 − x,Ni x)O 3 thin films by optical transmittance technique

Abstract

Ba(Ti 1 − x ,Ni x )O 3 ferroelectric thin films with perovskite structure are prepared on fused quartz substrates by a sol–gel process. Optical transmittance measurements indicate that Ni-doping has an obvious effect on the energy band structure of BaTiO 3. It has been found that the refractive index n, extinction coefficient k, and band gap energy E g of the films are functions of the film composition. The E g of Ba(Ti 1 − x ,Ni x )O 3 decreases approximately linearly as the Ni content increases, which is attributed to the decline of conduction band energy level with increasing the Ni content. On the other hand, n and k both increase linearly with increasing the Ni content because of the increase of packing density. These results indicate that thin films might have potential applications in BaTiO 3-based thin-film optical devices.