Examples of microanalytical investigations show, that differences in the chemical and physical interactions between the substrates and adjacent material can occur, which can induce structural and compositional changes of the surface and whithin subsurface layers during the pretreatment of the substrates before coating. In particular, pretreatment can influence the properties and the optical properties of the optical surfaces on glass. Moreover, the deposition techniques also contribute to changes of the properties at the same time. Microanalysis can reveal chemical reactions also, by which different crystal-line or non-crystalline interfacial and subsurface layers are formed during processing at elevated temperatures, and which produce different surface properties depending on the processing parameters. This can be exemplified when analytical electron microscopy is applied together with in-depth profiling in combination, which provide the large spatial resolution required for these investigations. The lateral resolution of the analytical electron microscopy allows studying the formation of defects with dimensions smaller than 1 pm. The comparison of the various microanalysis results with the respective product properties and their dependence on the fabrication parameters provides data for process control and for obtaining a high degree of reproducibility of optical properties, which otherwise cannot be obtained. Concepts must be developed because of economy selecting the most adequate analysis methods for obtaining the required data.
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