Structure and optical properties of Ba_0.9Sr_0.1TiO₃ ferroelectric thin films prepared by chemical solution routes

Barium strontium titanate (Ba_0.9Sr_0.1TiO₃) ferroelectric thin films have been grown on Pt/Ti/SiO₂/Si substrates by a modified chemical solution route. X-ray diffraction and Raman spectroscopy measurements show that the films have an excellent crystallinity and crystallize in a tetragonal structure. Field-emission scanning electron microscopy and atomic force microscopy investigations show that the films have a columnar structure with large grains of 80-200 nm in diameter. For an electric field of 320 kV/cm, the remnant polarization and the coercive field are 7.8 μC/cm² and 56 kV/cm, respectively. The optical constants (n, k) of the Ba_0.9Sr_0.1TiO₃ thin films are obtained by spectroscopic ellipsometry in the spectral range between 0.3 and 1.7 μm, and the band-gap energy is determined to be approximately 3.6 eV.