Single-crystal growth of NaCl-structure Al-Cr-N thin films on MgO(0Â 0Â 1) by magnetron sputter epitaxy

Single-crystal NaCl-structure Al0.68Cr0.32N thin films were deposited onto MgO(0 0 1) substrates. The films exhibit cube-on-cube epitaxial growth with an initial pseudomorphic strained layer before complete relaxation into an isotropic lattice parameter of 4.119 Å as shown by symmetric high-resolution X-ray diffraction and asymmetric reciprocal space maps. The relaxation proceeds via a threading dislocation network as revealed by transmission electron microscopy. Films of 900 nm thickness have a hardness of 32.4 ± 0.5 GPa, an elastic modulus of 460.8 ± 5 GPa, and a room-temperature resistivity of 2.7 × 103 Ω cm as determined by nanoindentation and four-point probe measurements, respectively.