Orientation control of KNbO3 film grown on glass substrates by Ca2Nb3O10− nanosheets seed layer

ABSTRACT KNbO3 films have been deposited by pulsed laser deposition on glass substrates covered by Ca2Nb3O10− nanosheets used as seed layer, for the purpose of promoting (001) preferential orientation. Nanosheets have been prepared by the exfoliation process of HCa2Nb3O10 phase that is obtained by cation exchange of the Dion-Jacobson KCa2Nb3O10 phase in an acidic solution. Electron diffraction in transmission electron microscopy performed on KCa2Nb3O10 and HCa2Nb3O10 powders, and on Ca2Nb3O10− nanosheets revealed formation of local superstructures that are not detected by X-ray diffraction due to the weakness of superstructure reflection intensities. Nanosheets were deposited on substrates using the Langmuir-Blodgett method. A smooth covering of the surface was shown by atomic force microscopy. 200 nm thick KNbO3 films have been grown by pulsed laser deposition on Ca2Nb3O10−-NS/glass and on (001)SrTiO3 substrates for comparison. Substrates covered with nanosheets induced highly textured (001)-oriented thin film, which possesses a similar microstructure as epitaxial film on single crystalline strontium titanate substrate.