Analysis of optical and related properties of tin oxide thin films determined by Drude-Lorentz model

作者：Kadi Mohamed; Smaali Assia; Outemzabet Ratiba^*

来源：Surface and Coatings Technology, 2012, 211: 45-49.

DOI：10.1016/j.surfcoat.2011.10.027

• Tin oxide
• Thin films
• Dispersion
• Refraction
• Extinction
• Doping

In this paper, optical parameters, such as refractive index n and extinction coefficient K, of tin oxide thin films determined by fitting the measured and simulated optical reflectance spectra, are presented and analysed. Among the various classical dispersion relations for the dielectric function, we use the Drude model combined with the Lorentzian oscillators to get a good fit of R in the measured spectral range. Results on related parameters such as high frequency dielectric constant, plasma frequency, relaxation lifetime, electron density, film thickness and band gap are discussed. Pure tin oxide films deposited at different temperature exhibit the same reflectance behaviour in the entire range while antimony doped films exhibit a deep minimum of reflectance in the visible domain and a maximum in the infrared domain. The results show also that the refractive index and extinction coefficient of antimony-doped SnO2 films increase with the increase of the Sb/Sn ratios. The dispersion of K of doped films is higher than that the undoped ones in a wide photon energy spectral range while the dispersion of n exhibit an opposite behaviour. The high frequency dielectric constant a. decreased with increasing percentages of Sb in SnO2 and the optical band gap Eg depend on the doping amount. The deposited films present a great reflection in the NIR wavelength region which may originate from the fact that these layers contain many carriers resulting in a large nonstochiometry in the chemical composition. The optically determined film thickness agrees with that obtained by ellipsometty.

• 出版日期2012-10-25