Abstract
Polycrystalline CrNx films on Si(100) and glass substrates and epitaxial CrNx films on MgO(100) substrates were fabricated by reactive sputtering with different nitrogen gas flow rates (fN(2)). With the increase of f(N2), a lattice phase transformation from metallic Cr2N to semiconducting CrN appears in both polycrystalline and epitaxial CrNx films. At f(N2) = 100 sccm, the low-temperature conductance mechanism is dominated by both Mott and Efros-Shklovskii variable-range hopping in either polycrystalline or epitaxial CrN films. In all of the polycrystalline and epitaxial films, only the polycrystalline CrNx films fabricated at f(N2) = 30 and 50 sccm exhibit a discontinuity in rho(T) curves at 260-280 K, indicating that both the N-vacancy concentration and grain boundaries play important roles in the metal-insulator transition. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4772682]