Browsing by Author "Großkopf, Klaus"

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    Excimer laser processing of BK7 and BGG31 glasses
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1993) Nowak, Rainer; Metev, Simeon; Sepold, Gerd; Großkopf, Klaus
    Large-area excimer laser processing of BK7 and BGG31 glasses was investigated for laser etching and laser-assisted metallization. Laser etching experiments were performed at wavelengths of 193, 248 and 308 nm and energy densities up to 5 J/cm^2 in various inert and reactive gases. The investigations revealed a good applicability of ArF excimer lasers for nondestructive laser etching of glass. The laser etching behavior is characterized by a characteristic threshold energy density of the order of 1 J/cm^2. Below this threshold laser etching is achieved only in reactive gases and is typically of the order of 0.1 nm/pulse. Above this specific threshold energy density the etch rate rapidly increases and is practically independent of the gas nature but depends more strongly on the gas pressure. In this ablation region the etch rate is of the order of 0.1 µm/pulse. A qualitative thermal model describing laser etching of glass in the ablation region is discussed. Laser-assisted metallization of glass surfaces has been achieved upon excimer laser irradiation of thin organometallic films on the glass surface and post-processing by electroless plating. Metallic nickel deposits showed a good adhesion and structures of a size between several 10 µm and a few millimeters were produced
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    In-depth analysis of elements and properties of hydrated subsurface layers on optical surfaces of a SiO2-BaO-B2O3 glass with SIMS, IBSCA, RBS and NRA Part 1. Experimental procedures and results
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1987) Bach, Hans; Großkopf, Klaus; March, Peter; Rauch, Friedrich
    The formation of thin subsurface layers was studied which occurred during the chemical interaction of polished and cleaned optical surfaces with different slurries before and after covering them with λ/4-MgF2 coatings. By a suitable selection of the parameters for these chemical interactions a thickness of the subsurface layers was produced which allowed to meet the requirements of the various surface analysis methods. The thicknesses and the refractive indices of the subsurface layers could be calculated from the measured spectral reflectances. Slurries with a pH value < 9 were applied so that a leaching of glass components from the subsurface layers occurred. This was indicated by the refractive indices and was studied in detail by analyzing the in-depth distributions of the glass components. Distinct matrix effects could be disclosed from the in-depth profiles for SIMS and IBSCA by a comparison with the results of the quantitative analysis with RBS and NRA. These matrix effects were different within the subsurface layers from those observed for the bulk glass. The quantitative analysis of the hydrogen in-depth distributions by NRA allows for the first time to link differences in the matrix effects with a different hydrogen content within the subsurface layers.
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    In-depth analysis of elements and properties of hydrated subsurface layers on optical surfaces of a SiO2-BaO-B2O3 glass with SIMS, IBSCA, RBS and NRA Part 2. Discussion of results
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1987) Bach, Hans; Großkopf, Klaus; March, Peter; Rauch, Friedrich
    In the second part of this contribution it was derived from the comparison of the sputter yields with the specific energy losses within the bulk glass and within the various subsurface layers, that the differences in the matrix effects for SIMS and IBSCA between the bulk glass and the subsurface layers are caused by a decrease of the atomic densities and of the mean atomic bond energies within the subsurface layers as well. The knowledge of the matrix effects and their origin was most important for the interpretation of the SIMS and IBSCA in-depth profiles recorded for samples prepared with variations of the production parameters. E. g., various degrees of hydration and swelling could be distinguished by the influence of the different matrix effects on the in-depth profiles of the elements. The variations in the degrees of hydration of the subsurface layers could be ascribed to the influence of the thermal treatment before coating, to the interaction with slurries of different pH values and to the duration of storage before coating with λ/4-MgF2 layers. It is of importance for the fabrication of optical surfaces that the analysis results and the optical properties of the subsurface layers could be correlated with each other and with respective changes of the production parameters. The results illustrate that the properties of hydrated subsurface layers depend sensitively on a great variety of parameters which may be difficult to keep constant during processing. It is recommended, therefore, that such subsurface layers should be avoided whenever possible in optical fabrication to make it easier to attain the high reproducibility required for the optical properties.