Spectroscopic ellipsometry study of 0.5BaZr_(0.2)Ti_(0.8)O_3-0.5Ba_(0.7)Ca_(0.3)TiO_3 ferroelectric thin films

摘要

0.5BaZr_(0.2)Ti_(0.8)O_3-0.5Ba_(0.7)Ca_(0.3)TiO_3 thin films have been deposited on Pt/Ti/SiO_2/Si substrates by a modified sol-gel technique. The samples are well-crystallized perovskite ferroelectrics at room temperature, with good surface topography. Optical properties of these films in the 280-850 nm wavelength range have been investigated by spectroscopic ellipsometry at room temperature. The measured ellipsometry parameters are well fitted by Tauc-Lorentz oscillator dispersion formula. As the wavelength increases, the refractive index and extinction coefficient rise in the beginning and then descend, with a peak at about 300 nm. The calculated absorption coefficient demonstrates that as-grown films have selective absorption, with a broad transparent range, and possess a big energy gap (4.18 eV).