The influence of lattice mismatch and film thickness on the growth of TiO2 on LaAlO3 and SrTiO3 substrates

Titanium dioxide, in both anatase and rutile phases, is of interest for many industrial applications and, when doped with cobalt, as a room temperature ferromagnet. Although the metastable anatase forms of TiO2 are difficult to produce in bulk, they can be grown in thin film form by the choice of an appropriate lattice-matched substrate. We present the thickness dependence of lattice strain and crystalline quality for thin films of (0 0 1) oriented anatase grown on (0 0 1) LaAlO3 and (0 0 1) SrTiO3 substrates by pulsed laser deposition. For films on (0 0 1) LaAlO3 the crystalline quality decreases as the film thickness increases. However, for films grown on (00 1) SrTiO3, the film quality improves as the film thickness increases due to the lattice strain being relieved. We also show the epitaxial growth of TiO2 on both SrTiO3 (0 1 1) and (I 11) substrates. On (0 1 1) SrTiO3, anatase grows (0 12) oriented with an in-plane orientation of [0 10] anatase parallel to[100]SrTiO3. On (I 1 1) SrTiO3, single phase (10 0) oriented epitaxial rutile films are obtained, with an in-plane orientation of [0 0 1] rutile parallel to[011] SrTiO3. (C) 2003 Elsevier Science B.V. All rights reserved.