Fourier Transform Infra-red (FTIR) Spectroscopy provides information on molecular vibrations, and allows chemical fingerprinting of sample species. It is widely used for analysis of both organic and inorganic materials including contaminants. Spectra can be obtained in either transmission or reflectance, and small-area analysis is possible. Materials may be identified by comparison with library reference spectra, or spectra can be interpreted based on the presence of IR absorption bands characteristic of the functional groups present. Thin films can be quantitatively analysed or compared.