Depth Profiling Analysis using Resonant Raman Spectroscopy

J. J. LEANI; H. J. SÁNCHEZ; R.D. PÉREZ; C. A. PÉREZ

Campinas

Conferencia; IXCOM21; 2011

Total Reflection of X-rays is a largely proved spectroscopic technique that allows the study of materialsurfaces. As the refractive index is less than unity, X-rays incident on a material are, theoretically,totally reflected if the glancing angle is less than a critical angle derived from the Snell´s law. Makinguse of this relation, different depths of a sample could be studied by means of the correct election ofthe incident radiation angle [1].Resonant Raman scattering is an inelastic scattering process which presents fundamental differencescompared to other scattering interactions. This phenomenon becomes dominant when atoms areirradiated with incident energy lower and close to an absorption edge. Recently, a spectroscopictechnique in formation based in this process showed to be useful to distinguish surrounded chemicalenvironments [2,3].For the first time, both total reflection and resonant Raman scattering techniques are used combined inorder to discriminate oxidation states in nano-layers of materials. Samples of pure Cu and Fe oxidizedin water and salty water respectively, were studied in the LNLS of Brazil [4] scanning the incidentradiation angle around the critical angle with incident energy lower and close to the K absorption edgeof both elements.The RRS spectra were analyzed with specific programs for fitting the experimental data to theoreticalexpressions. Then, residuals were determined in the low energy side of the RRS peaks. These residualswere treated with FFT smoothing methods taking into account the instrument functions of thedetecting system. The residuals show an oscillation pattern that change smoothly with the incidentangle, i.e. with the depth, allowing a depth study of the oxidation state with nano-metric resolution.A RRS chemical environment technique in total reflection geometry will offer an opportunity to studyhow the oxidation state change with the depth in different kind of samples in which a completecharacterization is impossible to achieve by other methods, such as conventional absorptiontechniques.