Structural and Raman characterization of nanogranular BaTiO3-NiFe2O4 thin films deposited by laser ablation on Si/Pt substrates

Abstract

Thin films composed by (BaTiO3)(1-x)-(NiFe2O4)(x) with different nickel ferrite concentrations (x) have been deposited by pulsed laser ablation on platinum covered Si(001) substrates. The films structure was studied by X-ray diffraction and Raman spectroscopy. It was found that the NiFe2O4 phase unit cell was expanded along the growth direction of the films, with a lattice parameter that increased with increasing NiFe2O4 concentration. The opposite behavior was observed on the BaTiO3 phase, with an expansion of its unit cell that lowered with increasing x. The presence of the strain in the films induced a redshift of the Raman peaks of NiFe2O4 that decreased with increasing NiFe2O4 concentration. Cation disorder in the nickel ferrite was observed for lower x, where the nanograins are more isolated and subjected to more strain, which was progressively decreased for higher NiFe2O4 content in the films. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim