Tailoring of morphology and orientation of LaNiO3 films from polymeric precursors

The aim of this work was to prepare lanthanum nickel oxide (LaNiO3, LNO) thin films of different morphology and orientation. The precursor solutions were prepared by a chemical method from citric salts of lanthanum and nickel. Films were deposited using spin-on technique on Si (1 0 0) substrates. Tailoring of the films orientation and morphology has been attained through two thermal treatment processes with different heating devices: tubular furnace (process 1) and hot plate (process 2). Films were annealed at 600 and 700 °C, with heating rates: 20 °C/min (process 1) and 1 °C/min (process 2). Annealing times were from 30 min to 20 h. LNO films were characterized by AFM and X-ray diffraction analysis. Depending on the heating process applied, the obtained films showed very different structures, from completely amorphous to well crystallized and highly oriented. Films treated by process 1 were polycrystalline, had smaller oval grains and lower roughness parameters than films heated on a hot plate. Due to the low heating rate and heating from the substrate side, films obtained through process 2 were highly (1 1 0) oriented with elongated grains aligned along one direction.