Quantitative chemical composition of thin films with infrared spectroscopic ellipsometry: application to hydrated oxide films on aluminium

Abstract

A method to quantify the composition of thin films using infrared spectroscopic ellipsometry (IRSE), supplemented by visible spectroscopic ellipsometry (VISSE), is proposed. Because ellipsometry measures the thickness and optical constants of a surface layer simultaneously, the absorption coefficient of the film as a function of wavelength can be obtained. Using values of the absorption coefficients for the pure components of the film, the percentages (mol.% or wt.%) of each component in the film can be calculated. The method is demonstrated in a study of the hydration of oxide films on electropolished aluminium and the anodically formed barrier oxide film. The IRSE technique shows that hydration of the films by immersion in boiling water results in the conversion of aluminium oxide to pseudoboehmite.

The characterization of the interfacial interaction between polymeric methylene diphenyl diisocyanate and aluminum: a ToF‐SIMS and XPS study

“…When the aluminum substrate is taken out from the boiling deionized water, the aluminum surface has high surface‐free energy and, hence, the adventitious hydrocarbon is adsorbed on the surface. By hydration, the aluminum surface becomes porous as a result of a formation of pseudoboehmite,6, 14–15 and,, hence, more surface area leads to the reduction of the adventitious carbon concentration compared with the degreased substrate. Since OC (BE = 532.0–532.1 eV) and OC (BE = 533.2–533.6 eV) components can also be observed in the O1s peaks, the cross reference of C1s and O1s peak fits allow to quantify aluminum oxide (O 2− ) and hydroxide (OH − ) components of O1s.…”

Study of the effect of different aluminium surface pretreatments on the deposition of thin non‐functional silane coatings

“…The second peak, showing the most important changes as a function of the storage and pretreatment conditions, is due to pseudoboehmite (AlOOH). 12 As expected, an alkaline pretreatment enhances the dissolution of the oxide layer and allows the precipitation of hydroxyl groups at the remaining oxide according to the model described by Vedder and Vermilyea. 13 Another support for the presence of pseudoboehmite is the asymmetric peak at around 3500 cm 1 .…”

“…13 Another support for the presence of pseudoboehmite is the asymmetric peak at around 3500 cm 1 . Indeed, this peak can be deconvoluted into two components: one for the OH stretching of water (near 3500 cm 1 ) and one for the OH stretching of AlOOH (near 3300 cm 1 according to Van Gils et al 12 ). However, the peak at about 1100 cm 1 is relatively broad meaning that other absorptions may be present.…”

In situ ellipsometric and electrochemical characterisation of oxide formed on aluminium in acetate buffer

“…2. The refractive indices were based on literature values [1,5]. ψ mod and ∆ mod were computed by the equations of Azzam and Bashara [6] for polarised light reflected from a layered structure of different materials of uniform thickness positioned on each other.…”

“…Most of the available work in this subject is based on ex-situ spectroscopic techniques [1][2][3]. The surfaces characterised ex situ may be quite different from the actual surface during reactions between the organic molecules and the oxide covered aluminium surface in a solution.…”