Optical properties and band gap characterization of high dielectric constant oxides

Abstract The optical characterization of amorphous and crystalline HfO 2 , SrHfO 3 , BaZrO 3 , BaHfO 3 , BaHf 0 . 5 Ti 0 . 5 O 3 , SrTiO 3 , Sr 2 Ta 2 O 7 and Ta 3 Ti 2 O x high dielectric constant thin (15–50 nm) films was performed using a combination of spectroscopic ellipsometry and reflectometry in the photon-energy range 1.5–6.8 eV. The optical dielectric function, absorption coefficient, optical band gap energies E g , Urbach energy E u and 3D interband critical point energies were obtained from these studies. The E g as well as the E u of the dielectric materials are important for device performance. Indirect E g was obtained for all materials investigated. Lower E g tends to result in higher value of permittivity κ. The results obtained deliver the necessary information for the selection of alternative high-κ dielectrics with adequate E u , E g and κ values and additionally provide optical metrology for such films.