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 degrees C in a mixed gas atmosphere of 100 mTorr N(2)/O(2) (similar to 20:1). The dielectric permittivity, kappa, 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, tau(kappa), 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.