4 November 1994 Surface contamination of bare substrates: mapping of absorption and influence on depostited thin films
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Proceedings Volume 2253, Optical Interference Coatings; (1994) https://doi.org/10.1117/12.192177
Event: 1994 International Symposium on Optical Interference Coatings, 1994, Grenoble, France
Photothermal Deflection (PD) is used for mapping very small absorption losses (as low as 10-6). Measurements performed on bare substrates have shown the existence of highly non uniform absorption localized on the substrate surface. High absorption sites can be twenty times as absorbing as the mean value while we can find areas with very low absorption (approximately equals 10-6). Typically for fused silica substrates, the mean value of surface absorption is about 8 X 10-6. Comparisons between PD mapping, Nomarski microphotography and scattering mapping on the same area show that PD can give specific information about substrate-surface contamination. We have studied on different sets of substrates the influence of polishing and cleaning. We conclude that very smooth surfaces have a lower mean value of absorption then conventionally polished ones. For films deposited on fused silica substrates, we have observed precise correlation between absorption mappings on the same area of the bare then coated substrate.
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Mireille Commandre, Pierre J. Roche, Jean-Pierre Borgogno, and Gerard Albrand "Surface contamination of bare substrates: mapping of absorption and influence on depostited thin films", Proc. SPIE 2253, Optical Interference Coatings, (4 November 1994); doi: 10.1117/12.192177; https://doi.org/10.1117/12.192177

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