Optical characterization and microstructure of BaTiO ₃ thin films obtained by RF-magnetron sputtering

BaTiO ₃ thin films were deposited on Pt/Ti/SiO ₂ /Si by rf planar-magnetron sputtering. The films thickness increases with the decrease of both deposition pressure and sample-discharge centre distance. The films annealed at 900 °C, for 8 h, present direct band gap energy ranged between 3.57 and 3.59 eV. The dependence of the structure and microstructure (texture, degree of crystallinity), as well as of the optical characteristics on the deposition parameters, was analysed. Using spectroscopic ellipsometry (SE) measurements coupled with the Bruggeman Effective Medium Approximation (B-EMA), the layer structure and the surface roughness, were determined. The root mean square roughness values of the surface layer, estimated by atomic force microscopy (AFM) analyses, are ranged between 10 and 20 nm and were in good agreement with SE data. The obtained films have tetragonal unit cell and show densely packed, non-columnar morphology and hexagon-like crystallite shape.