Epitaxial suppression of the metal-insulator transition in CrN

Both single- and polycrystalline CrN layers are grown by reactive sputtering on MgO and quartz substrates, respectively. Temperature-dependent x-ray diffraction indicates a phase transition near 280 K to a low-temperature orthorhombic phase for polycrystalline CrN, while epitaxial constraints cause single-crystal CrN(001) and CrN(111) to remain in the cubic high-temperature phase. Electronic transport measurements indicate variable-range-hopping for the cubic phase below \ensuremath{\sim}120 K, a discontinuity at the phase transition for the polycrystalline layers, strongly and weakly disordered metallic conduction for the orthorhombic phase if deposited at 600 and 800 \ifmmode^\circ\else\textdegree\fi{}C, respectively, and a disorder-induced metal-insulator transition in the cubic phase.