An easy sol–gel route for deposition of oriented Ln2Ti2O7 (Ln=La, Nd) films on SrTiO3 substrates

The effect of the orientation of SrTiO3 (STO) substrates, (1 0 0) or (1 1 0), on the growth of La2Ti2O7 (LTO) and Nd2Ti2O7 (NTO) thin films was investigated. The films were deposited via a sol–gel process coupled to the spin-coating technique. Depending on the substrate orientation, a similar effect was observed on the structural properties for both the LTO and NTO thin films. For (1 1 0)-oriented STO substrate, the films are preferentially (0 0 1) oriented while for (1 0 0)-oriented STO substrates, the orientation is mainly (0 1 2). Those matching appear to be in good agreement with the compatibility between the film/substrate crystal lattices, in relation with the existence of perovskite slabs in Ln2Ti2O7 (Ln=rare earth) compounds. In these latter, a slight disorientation of the (0 1 2) planes with respect to the surface of the substrate was measured. This tilting is even more marked in the case of NTO. The surface morphology was studied by atomic force microscopy.