Optical band gap of BiFeO3 grown by molecular-beam epitaxy

BiFeO(3) thin films have been deposited on (001) SrTiO(3) substrates by adsorption-controlled reactive molecular-beam epitaxy. For a given bismuth overpressure and oxygen activity, single-phase BiFeO(3) films can be grown over a range of deposition temperatures in accordance with thermodynamic calculations. Four-circle x-ray diffraction reveals phase-pure, epitaxial films with omega rocking curve full width at half maximum values as narrow as 29 arc sec (0.008 degrees). Multiple-angle spectroscopic ellipsometry reveals a direct optical band gap at 2.74 eV for stoichiometric as well as 5% bismuth-deficient single-phase BiFeO(3) films. (C) 2008 American Institute of Physics.