MIGUEL Maria De La Paz
congresos y reuniones científicas
Experimental determination of the Point Spread Function in depth profiling by Confocal Raman microscopy
Otro; -CAMP 2011-Inter-Continental Advanced Materials for Photonics Summer/Winter School; 2011
Experimental determination of the Point Spread Function in depth profiling by Confocal Raman microscopy   Confocal Raman microscopy is a very useful tool to study polymer films, particularly those transparent, in order to characterize chemical nature, distribution of components, physical and structural properties or interphases evolution, as a function of depth. Transparent materials are usually probed in depth with the classic metallurgical objectives by virtue of the minimal sample preparation required. However, it is well known that Confocal Raman measurements are optically distorted by a combination of laser refraction at the sample entrance, diffraction and the presence of the confocal aperture. The challenge of properly interpreting experimental data subjected to the above mentioned distortions has driven the development of mathematical models to estimate the point spread function (PSF), i.e. how broad is the instrumental response as a function of focusing depth. It has been possible through the study of model systems with known response, for example, films of known thickness in contact with a substrate through a planar interface, to validate the measured response by comparison with that predicted, on the base of the calculated PSF. However, no attempts have been made to measure and characterize directly the PSF in Confocal Raman, as a function of focusing depth and for a given set of operative conditions. This is useful not only to compare the results obtained with model predictions, in order to improve those models, but also to help in the optimization of instrumental design. In this work we present the design of an experiment that allows direct determination of PSF as a function of depth in Confocal Raman microscopy. It is based on depth slicing a thin molded polystyrene wedged-shape film fixed on the surface of a silicon wafer pasted on a slide, and determining the Si response buried at different depths. The point spread function experimentally determined under different conditions will be compared with results predicted by theoretical models.