Use of optical methods to characterize thin silane films coated on aluminium

For corrosion and adhesion problems, the aluminium and its alloys are usually modified by different surface treatments. Silane coupling agents that are an alternative treatment for the chromate-containing pretreatment are being used more frequently in industry. This paper focuses on the study of a no-rinse system using the non-functional silane bis-1,2-(triethoxysilyl)ethane (BTSE). The objective of this work is to study the effect of curing BTSE films coated on aluminium substrates. Spectroscopic ellipsometry is used to determine the thickness and optical constants of the silane coatings as a function of the curing conditions. It is shown by infrared spectroscopic ellipsometry (IRSE) how the curing causes changes in the chemistry of silane films deposited on aluminium. Indeed, IRSE combines the advantages of the traditional Fourier transform infrared spectroscopy method (molecular information via knowledge of the infrared absorption bands) with those of spectroscopic ellipsometry (morphological information such as film thickness and optical information such as refractive index and extinction coefficient). Copyright (C) 2002 John Wiley Sons, Ltd.