Characterisation of sol-gel thin films by spectroscopic ellipsometry

Abstract

The refractive index and porosity of silicate based sol-gel thin films prepared from tetraethoxysilane and methyltriethoxysilane were characterised using spectroscopic ellipsometry. With the hypothesis of considering the thin films as one mixture of matrix materials with pores for ellipsometric data analysis, linear calculation and effective medium approximation (EMA) models were employed in ellipsometric data analysis. The analysis ambiguity with EMA model was effectively reduced by incorporating the intensity of reflectance of thin films in the data analysis. Results show that data analysis using EMA model with Cauchy equation can significantly improve the accuracy in the determination of the film porosity and refractive index. This approach greatly enhances the applicability of ellipsometry in analysis of porous thin films. © 2006 IOP Publishing Ltd.