Abstract

The use of conventional transmission-absorption spectroscopy to study solid surfaces is limited to those cases where optically transparent samples can be prepared. When the solid is a metal or a metal oxide, this condition can only be satisfied by using very thin films in order to minimize absorption and scattering losses, which in turn leads to a lack of sensitivity because of the small amount of sample present in the beam path. Another technique should therefore be chosen, and internal reflection seems to offer several advantages. The metal or metal oxide film can be supported on an infrared-transparent solid, and the beam of radiation can propagate within it by a series of total internal reflections. An evanescent wave actually penetrates into the sample at each point of reflection, and therefore absorption of radiation can take place for a particular wavelength. As a result, the beam of radiation will emerge attenuated. In this way, the scattering problem is eliminated, and the possibility of multiple reflections leads to an increase in sensitivity.

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Opt. Mater. Express 5(9) 1898-1909 (2015)

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