Band gap in epitaxial NaCl-structure CrN(001) layers

Abstract

B1-NaCl-structure CrN(001) layers were grown on MgO(001) at 600°C by ultrahigh vacuum reactive magnetron sputter deposition in pure N 2 discharges. X-ray diffraction analyses establish the epitaxial relationship as cube-on-cube, (001) CrN∥(001) MgO with [100] CrN∥[100] MgO, while temperature-dependent measurements show that the previously reported phase transition to the orthorhombic P nma structure is, due to epitaxial constraints, absent in our layers. The resistivity increases with decreasing temperature, from 0.028 cm at 400 K to 271 cm at 20 K, indicating semiconducting behavior with hopping conduction. Optical absorption is low (α<2×10 4cm -1) for photon energies below 0.7 eV and increases steeply at higher energies. In situ ultraviolet photoelectron spectra indicate that the density of states vanishes at the Fermi level. The overall results provide evidence for CrN exhibiting a Mott-Hubbard type band gap. © 2002 American Institute of Physics.