The influence of lattice mismatch and film thickness on the growth of TiO 2 on LaAlO 3 and SrTiO 3 substrates

Abstract

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 TiO 2 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) LaAlO 3 and (0 0 1) SrTiO 3 substrates by pulsed laser deposition. For films on (0 0 1) LaAlO 3 the crystalline quality decreases as the film thickness increases. However, for films grown on (0 0 1) SrTiO 3, the film quality improves as the film thickness increases due to the lattice strain being relieved. We also show the epitaxial growth of TiO 2 on both SrTiO 3 (0 1 1) and (1 1 1) substrates. On (0 1 1) SrTiO 3, anatase grows (0 1 2) oriented with an in-plane orientation of [0 1 0] anatase ∥[1 0 0]SrTiO 3. On (1 1 1) SrTiO 3, single phase (1 0 0) oriented epitaxial rutile films are obtained, with an in-plane orientation of [0 0 1] rutile ∥ [01 1 ̄ ] SrTiO 3.