Grazing-Incidence Resonant Raman Scattering

H.J. SÁNCHEZ; JUAN JOSÉ LEANI; D. PEREZ; C.A. PEREZ

Osaka

Conferencia; 15th International Conference on Total Reflection X-Ray Fluorescence Analysis and Related Methods (TXRF2013); 2013

The Japan Society for Analytical Chemistry y Osaka University

Total reflection of x-rays is a photon effect that gives place to many spectrometric techniques allowing the study of material surfaces. Since the pioneer work of Parrat [1] in 1954 for surface studies of solids by the analysis of the reflected x-ray intensity, many works have been published showing the potentiality of this phenomenon combined with other techniques, as X-ray Florescence (XRF) in a variety of samples, Extended X-ray Absorption Fine Structure (EXAFS) and even Inelastic X-ray Scattering (IXS) at grazing incidence conditions was achieved at several studied energies. Generally, in order to obtained chemical environment information, these techniques probe edge structure characteristics by tuning the incident energy towards the edge. In the last few years, inelastic X-ray scattering experiments has become a powerful tool for investigating electronic excitations and electronic ground-state properties of many-electron systems. In particular, there is an increasing interest to employ this technique using incident monochromatic radiation at fixed energy, i.e. without the need of an incident energy scan, in combination with high-resolution systems to obtain local structure information, similar to the one obtained with X-ray Absorption Near Edge Structure (XANES) spectroscopy. Both x-ray total reflection and x-ray Raman scattering techniques were combined to discriminate chemical environments in depth profiling studies using an energy dispersive system. This allowed, for the first time, to resolve oxidation state on surface nano-layers with a low resolution system. Samples of pure Cu and Fe oxidized in tap water and salty water respectively were studied in the Brazilian synchrotron facility using monochromatic radiation and an EDS setup. The measurements were carried out in total reflection geometry with incident energy lower and close to the K absorption edge of both elements. The results allowed observing the presence of very thin oxide layers, usually not observable with conventional geometries of irradiation. They also permit the identification of the compound present in a particular depth of the sample with nanometric, or even sub-nanometric, resolution using a low-resolution system.