Formation of Mobile Hydridic Defects in Zirconium Nitride Films with n-Type Semiconductor Properties

Abstract

The incorporation of mobile hydridic defects was demonstrated for low-crystalline zirconium nitride (Zr3N4−δ) films deposited by radio frequency reactive sputtering under a flow of nitrogen-rich reactive gases. Extended X-ray adsorption fine structure analysis confirmed that the local coordination environment around the Zr atoms was very close to that of the orthorhombic Eu3O4 phase. Pristine Zr3N4−δ films exhibited n-type semiconductor behavior due to the presence of nitrogen vacancy donors with a carrier concentration of 1.4 × 1020 cm–3 and an electron mobility of 2.2 × 10–3 cm2 V–1 s–1 at room temperature. Electrochemical and spectroscopic measurements confirmed that Zr3N4−δ was readily hydrogenated upon exposure to H2 gas at 300 °C to form hydridic defects via electron donation to hydrogen adatoms. Hence, the hydrogenated film exhibited H– ion/electron mixed conductor behavior in a H2 atmosphere. These findings open the possibility for exploring new hydride ion conductors based on thermodynamically stable transition metal nitrides.