Changes in the electric resistivity of CrN subsequent to oxygen dissolution

Single-phase epitaxial chromium oxynitride thin films containing 11 to 45 mol% oxygen were successfully synthesized on MgO(100) substrates by pulsed laser deposition at 773K while controlling the ambient oxygen partial pressure. The film compositions were subsequently analyzed by Rutherford backscattering spectroscopy and electron energy-loss spectroscopy, while crystal phases were identified by X-ray diffractometry using the Bragg-Brentano and glancing incidence configurations and by in-plane phi scanning. The microstructures were observed by transmission electron microscopy. The electrical resistance of the films was determined by either the two-or four-probe method. The Cr(N, O) thin film having 11 mol% oxygen exhibited a metallic temperature dependence. In contrast, the films containing oxygen of 13 mol% or higher showed a semiconducting (or insulating) temperature dependence. This resistivity change is believed to result from enhanced electron correlation brought about by increases in oxygen content, sufficient to transform the Cr(N, O) thin film into a Mott insulator. (C) 2016 The Japan Society of Applied Physics