Epitaxial Thin-Film Deposition and Dielectric Properties of the Perovskite Oxynitride BaTaO₂N

Pulsed-laser deposition was employed to grow epitaxial thin films of the oxynitride perovskite BaTaO 2 N on a conducting SrRuO 3 buffer layer deposited on a 100-cut SrTiO 3 single-crystal substrate. Phase purity and epitaxy were optimized at a substrate temperature of 760 °C in a mixed gas atmosphere of 100 mTorr N 2 /O 2 (∼20:1). The dielectric permittivity, κ, of the BaTaO 2 N film was large, exhibiting a slight frequency dependence ranging from about 200 to 240 over the frequency range 1−100 kHz. Furthermore, over the temperature range 4−300 K the permittivity showed minimal variation as a function of temperature. The temperature coefficient of the dielectric constant, τ κ, is estimated to be in the range of −50 to −100 ppm/K. The coexistence of high dielectric permittivity and weak temperature dependence is an unusual combination in a single-phase material.