采用化学溶液沉积法在Pt/Ti/SiO2/Si衬底上制备了厚度小于100nm的Bi3.25La0.75Ti3O12(BLT)铁电薄膜,测量了光子能量为2～4.5eV的紫外可见椭圆偏振光谱.根据经典的电介质光学色散关系和五相结构模型,拟合获得薄膜在透明区和吸收区的光学常数、表面粗糙度、薄膜与衬底界面层以及BLT薄膜的厚度.薄膜在透明区的折射率色散关系可以通过单电子Sellmeier模型成功地进行解释.最后,根据Tauc′s法则,得到Bi3.25La0.75Ti3O12薄膜的直接禁带宽度为3.96eV.

Bi 3.25La 0.75Ti 3O 12 (BLT) ferroelectric thin films (<100nm) were deposited on Pt/Ti/SiO 2/Si substrates using chemical solution methods. The ultraviolet-visible ellipsometric spectra of the BLT thin films have been investigated in the photon energy range of 2～4.5eV. Based on the classical optical functions of the dielectrics and five-phase structure model, the optical constants of the BLT thin films in the transparent and absorption region, the surface roughness, the thicknesses of the BLT thin films and the interface layer between the films and substrates were simultaneously obtained by the fitting. The dispersion of the refractive index in the transparent region fitted well to a single-term Sellmeier relation. Finally, a 3.96ev direct band gap of the Bi 3.25La 0.75Ti 3O 12 thin films was obtained employing Tauc's principle.