  Electronic states of a correlated material can be effectively modified by
structural variations delivered from a single-crystal substrate. In this
letter, we show that the CrN films grown on MgO (001) substrates have a (001)
orientation, whereas the CrN films on {\alpha}-Al2O3 (0001) substrates are
oriented along (111) direction parallel to the surface normal. Transport
properties of CrN films are remarkably different depending on crystallographic
orientations. The critical thickness for the metal-insulator transition (MIT)
in CrN 111 films is significantly larger than that of CrN 001 films. In
contrast to CrN 001 films without apparent defects, scanning transmission
electron microscopy results reveal that CrN 111 films exhibit strain-induced
structural defects, e. g. the periodic horizontal twinning domains, resulting
in an increased electron scattering facilitating an insulating state.
Understanding the key parameters that determine the electronic properties of
ultrathin conductive layers is highly desirable for future technological
applications.
