Raman microscopy

Raman microscopy is a very specialized optical microscopy in which a conventional optical microscope is coupled to a Raman spectrometer or a Raman filter. The sample is illuminated with monochromatic light (a laser) and the Raman spectrum of the light scattered by the material is analyzed for different points of the sample.

Raman microscopy can resolve parts with different chemical composition in a sample, and, together with infrared microscopy, is sometimes referred as chemical imaging. It has been applied to the study of thin films, coatings, microelectronic integrated circuits, photonic devices, mineral inclusions, pigments in art works, identification of narcotics and plastic explosives, biological tissues, and others.

As in any optical microscopy, the spatial resolution of Raman microscopy in the far field is limited by the diffraction of light and is close to the micrometer (1/1000 mm). But the introduction of near field techniques like tip-enhanced Raman spectroscopy (TERS) can surpass this limitation and resolutions of tens of nanometers can be achieved.

• See, for example, G. Turrell and J. Corset, eds., Raman Microscopy. Developments and Applications (Academic Press, London, 1996).

Examples

The following figures illustrate the application of Raman microscopy to chemical imaging in materials science. The data were obtained at the Raman Microscopy Lab of the Materials Science Institute of Madrid, CSIC, in collaboration with other groups.