Atomic layer deposition of TiO2 from TiCl4 and ozone on single crystal alpha-Al2O3 substrates was investigated and the possibility to control the phase composition by the substrate orientation was demonstrated. Epitaxial growth of ruffle and high-pressure TiO2-II on alpha-Al2O3(0 0 0 1) and rutile on alpha-Al2O3(0 1 (1) over bar 2) were obtained at 400-600 degrees C. On alpha-Al2O3(0 0 0 1), the epitaxial relationships were determined to be [0 0 1](R) [2 (1) over bar (1) over bar 0](S) and [0 0 1](R) // [0 1 (1) over bar 0]S for rutile and sapphire, and [0 0 1](II) // [2 (1) over bar (1) over bar 0](s) and [0 (1) over bar 0](II) // [0 1 (1) over bar 0](S) for TiO2-II and sapphire. The TiO2-II concentration up to 50% was obtained in the films deposited at 425-500 degrees C. On alpha-Al2O3(0 1 (1) over bar 2), the epitaxial relationship of rutile was [0 1 0]R // [2 (1) over bar (1) over bar 0](S) and [0 0 1](R) // [0 1 (1) over bar 0]S. The densities of epitaxial films reached 42-4.3 g/cm(3) on substrates with both orientations but the epitaxial quality was markedly higher on alpha-Al2O3(0 0 0 1). (C) 2015 Elsevier B.V. All rights reserved.