
272 Semiconductor Device-Based Sensors for Gas, Chemical, and Biomedical Applications
© 2011 by Taylor & Francis Group, LLC
multiple species and pinpoint a specic species as well because the extinction coefcient is wave-
length dependent.
Raman scattering shifts the wavelength of the scattered photon. The wavelength shift is deter-
mined by the vibrational or rotational energy of a molecule. Thus, Raman spectroscopy can be
used for material analysis and chemical sensing. Raman spectroscopy is especially powerful for
obtaining vibrational spectra in an aqueous medium because water shows very weak Raman
scattering but strong IR abso ...