Single and Double-Layer Antireflection Coatings on Silicon


Abstract: In this study, the effect of single and double-layer thin film coatings on the reflectance spectrum of silicon surfaces has been investigated. Thin film coatings have been prepared by vacuum evaporation of the materials with suitable refractive index. Reflectance measurements in the visible and near infrared have shown that the coated samples acquire antireflection properties. Thickness and wavelength dependence of the antireflection properties of SiO, CeO_2 and ZnS single-layer coatings with optical thickness of one quarter wavelength has been studied. In double-layer coatings, a thin film of SiO, CeO_2 and ZnS with optical thickness of quarter wavelength were used as inner layer while a thin film of MgF_2 with equal optical thickness was used as outer layer. It was shown that double-layer coatings can produce a significantly broader low reflectance region than does the single-layer coating. The results have been discussed by considering the zero reflectance conditions for the refractive index and the optical thickness of layers.


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