Optical Characterization of Sr_(1-x)Ba_xBi_4Ti_4O_(15) Graded Thin Films

摘要

Sr_(1-x)Ba_xBi_4Ti_4O_(15) (SBBT) thin films with various Ba~(2+) contents (x = 0, 0.2, 0.4, 0.6, 0.8, 1.0) were prepared by Sol-Gel technique. Based on the precursors with different x values, SBBT graded thin films with gradients in composition were fabricated using a special heating treatment procedure below 800°C. The band edge absorption of SBBT graded thin films was between that of BBTi and SBTi films in the wavelength of 260 nm approx 350 nm. And the absorption peak position was about 469.2 nm and 611.8 nm, respectively. The average transmission ratio was about 76 percent, which was higher than that of mono-composition films. The optical band gap energy (Eg) of SBBT graded film was about 4.15 eV. Annealing conditions also have a great influence on the optical properties of the graded thin films. With the increase of annealing temperatures, the band edge absorption of SBBT graded thin film red-shifted and the optical band gap energy deceased monotonously.