Structural characterization of TiO2–Cr2O3 nanolaminates grown by atomic layer deposition

TiO2–Cr2O3 nanolaminates were atomic layer deposited on (0 1 2)-oriented sapphire and (1 0 0)-oriented silicon. The thickness of the alternating layers in the eight-layer laminates grown was close to 10 nm. The laminates were characterized by cross-sectional high-resolution transmission electron microscopy, high-resolution scanning electron microscopy, atomic force microscopy, reflection high-energy electron diffraction, and micro-Raman spectroscopy. A highly oriented growth of the laminate on sapphire and its growth with a very little preferred orientation on silicon were revealed. The laminate grown on sapphire had, along with better crystallinity, more exactly defined and more planar interphase boundaries. The amount of indefiniteness of the boundaries increased with the layer distance from the substrate. The crystalline phase of titania was rutile in the laminate grown on sapphire and anatase in the laminate grown on silicon, while the crystalline phase of chromia had eskolaite structure. In the laminate grown on sapphire, titania contained numerous twins; compressively strained chromia had in this case more perfect structure.