Investigation on the optical and structural properties of spin coated CeO 2-TiO 2 thin films

Abstract

Equimolar CeO 2-TiO 2 multi layer (3-7) thin films were prepared by spin coating technique in different spin speed (1500-4000 rpm), by using sol-gel route. The dependence of deposition conditions on the optical and structural properties of the films was investigated. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were employed to analyze the structural properties of the films. Optical constants (refractive index, absorption coefficient, energy band gap, etc.) were determined in the 200-1100 nm wavelength range by transmission spectrophotometry. It was found that with increasing spinning rate from 1500 rpm to 4000 rpm the thickness of the films decrease from 440 nm to 229 nm while the refractive index and the absorption coefficient at 550 nm wavelength increase from 1.80 to 2.16, and 599.83 cm -1 to 1174.60 cm -1 respectively. The thickness, refractive index, and absorption coefficient of the films at 550 nm wavelength increase from 235 nm to 548 nm, 1.85 to 2.00, and 553.90 cm -1 to 1347.00 cm -1 respectively with increasing the number of coating layers from 3 to 7. The optical band gap has a value of 3.19 eV for indirect transition and is independent of spin speed and number of layers. © 2006 WILEY-VCH Verlag GmbH & Co. KGaA.