An easy sol-gel route for deposition of oriented Ln_2Ti_2O_7 (Ln = La, Nd) films on SrTiO_3 substrates

摘要

The effect of the orientation of SrTiO_3 (STO) substrates, (100) or (110), on the growth of La_2Ti_2O_7 (LTO) and Nd_2Ti_2O_7 (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 (110)-oriented STO substrate, the films are preferentially (001) oriented while for (100)-oriented STO substrates, the orientation is mainly (012). 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 Ln_2Ti_2O_7 (Ln = rare earth) compounds. In these latter, a slight disorientation of the (012) 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.