Optical band gap of barium titanate nanoparticles prepared by RF-plasma chemical vapor deposition

The size dependence of the band gap for barium titanate nanoparticles prepared by RF-plasma chemical vapor deposition was investigated by measuring the diffuse reflectance spectra. The band gap of the indirect transition gradually increased, as the particle sizes decreased to less than 11.5 nm. Consequently, the band gap for particles of 6.7 nm in size was measured to be 3.47 eV, which was approximately 0.25 eV larger than that of BaTiO3 bulk. This phenomenon was discussed on the basis of quantum confinement model.