Raman scattering as a technique of measuring film thickness: interference effects in thin growing films

Simultaneous Raman-scattering and interferometric-thickness measurements have been made during the growth of sodium sulfate films on Pt/10%Rh substrates. For the experimental geometry, the s-polarized Raman-scattered radiation exhibits oscillations in intensity as a function of film thickness, while no intensity oscillations are observed for the p-polarized Raman scattering. The experimental results are modeled by assuming the interference of the multiple reflections of the incident laser beam and the interference of the multiple reflections of the Raman-scattered radiation. The model predicts extreme oscillations in the Raman signal/film thickness relationship for the s-polarized Raman collection and only small oscillations for the p-polarized Raman collection, in qualitative agreement with the experimental results.