Epitaxial Thin Films of the Oxynitride BaTaO$_2$N Grown by Pulsed-laser Deposition

Pulsed-laser deposition has been used to grow epitaxial thin films of the oxynitride BaTaO$_2$N on MgO substrates and SrTiO$_3 $ substrates with and without SrRuO$_3$ buffer layers. The thin films have a relatively high dielectric constant in the order of 200\,-\,250 from room temperature down to 4.2K with no significant frequency dependence. This special property, which has not been found before in other materials, potentially makes it a good candidate for many dielectric applications. We argue that a new mechanism is required to understand the dielectric properties of BaTaO$_2$N.