Multiple reflections, interferometry

Optical techniques can be used to monitor optical thickness and dielectric constant parameters. This includes ellipsometry, multiple reflection interferometry (74), evanescent wave (75), and surface plasmon resonance spectroscopy techniques (43). Ellipsometry has been used widely and routinely to investigate film thickness of pol3mier brush films (76). For optical properties of films, it is important that the average film roughness and imiformity is specified. Often, sampling is localized by the spot size, such that it is necessary to probe and average different areas of a sample. 

Twin boundaries and low-angle grain boundaries can often be observed directly on intersection with the surface. Frequently, the small tilts associated with internal twinning (as in antiferroelectrics) may be observed by reflection microscopy or multiple-beam interferometry. The etch technique used to identify optical and electrical twins in quartz is of considerable practical importance in fabricating piezoelectric oscillator plates. ... 

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