Optimization of Grazing Angle ATR for the Analysis of Monolayers on Silicon
Interest in the analysis of monomolecular layers on silicon has grown signifi cantly with the development efforts for molecular electronic devices.1,2 The need now exists to probe layers a few nanometers in thickness reliably and reproducibly. Traditional FT-IR sampling techniques such as transmission or ATR typically measure samples or coatings on samples where the thickness is 3 orders of magnitude greater. Grazing angle refl ection techniques have been used successfully to measure monomolecular layers on refl ective substrates.3 However, in the case where silicon is the substrate, the refl ection spectrum contains the signature of the base material in addition to the monolayer and resolving the distinctive features of the surface fi lm becomes diffi cult. As early as 1966, Harrick saw the need for the analysis of thin fi lms on another substrate by ATR and provided detailed theoretical description of the phenomena.
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