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The surface electromagnetic wave (SEW) spectroscopy 1 with laser sources of the IR radiat on has demonstrated high sensitivity to the state of the surface. The measurements of SEW attenuation on the sample give the information about the sample conductivity, surface roughness and about the presence of oxide or adsorbate on the metal surface, especially If their absorption bands are in the spectral region where laser lines are available. High sensitivity of modern Fourier transform spectrometers allows to detect SEW excited by broadband source. We have used Fourier transform spectrometers FTS-20V (Digilab) and IFS-113 (Bruker) with liquid nitrogen cooled detectors (Hg-CD-Te). On the metal (Ag, Al, Au, Cu, V, Be) surface SEW were excited using aperture coupling. The experiment is schematically shown on the fig.1. IR radiation from interferometer was focused on the gap between the sample 3 surface and the screen 1 placed at the distance of the order of 100 μm. In such a way on the gap propagating along a metal SEW and bulk radiation above the metal are excited. SEW runs from the aperture coupler to the edge of the sample (this distance could be varied from 2 to 30 mm) and decouples into the bulk radiation on the edge. The second screen 2 above the edge cut the bulk radiation from the aperture coupler. If we change the distance between the screens it is possible to obtain SEW absorption coefficient at different frequences from the output intensity variation. Fig.2 shows SEW propagation length spectra for Au and Cu. For these metals and also for Ag 2 propagation length is proportional to the square of the wavelength as it is predicted by Drude model. For Al such dependence is valid in the oxide transperancy region, in the region 800-1000 cm -1 natural oxide film give absorption band shown on Oxide films are well recognizible also on Be and V. Thermal growth or oxide film was studied (rig.4).
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