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Top1. Introduction
Ellipsometry is a well-known Non-Destructive Evaluation (NDE) optical method for determining film thickness and optical properties. It measures the change in the state of polarization of light reflected from films’ surface. Fast ellipsometry methods, single or multi-wavelengths, have been adopted for monitoring film growth in situ, allowing for the precise control of film deposition processes (Muller, 2005). With time, several parameters have been separately and largely investigated, such as in-situ measurements of materials complex permittivity using reflection ellipsometry (Sagnard, 2005), and arbitrary refractive index profile of composite thin films (Ho, 1990).
The advancement of spectroscopic ellipsometers has extended the analytical power of ellipsometry to complex multilayer coatings, where several optical parameters (refractive index, extinction coefficient, film thickness, roughness anisotropy, etc.) can be determined simultaneously. In the last two decades, new generations of ellipsometers came up with additional specifications and techniques, such as spectroscopic ellipsometry (Jung, 2008), methods of calibration (Asinovski, 2008), stroboscopic illumination technique (Han, 2006), and customization (Acurion, 2004). Even apertureless optical near-field scanning microscope system was created by combining a commercially available atomic force microscope and an Ellipsometer (Karageorgiev, 2001). Moreover, ellipsometry became suitable for optical sensing (Arwin, 2001) and film sensing applications (Sinibaldi, 2013).
A big leap ahead was stepped forward by developing new techniques of imaging ellipsometry (IE), e.g. combined microscopy and Thin Film Characterization (TFC), which overcomes the limits of classical ellipsometry, the spatial resolution. Besides the determination of film thickness and optical properties, one receives high contrast ellipsometric images from the surface with highest resolution. Small samples, structured materials or inhomogeneous surfaces, which are beyond the capabilities of other ellipsometric tools, are now visible with IE and this opens new doors to a better understanding of today’s advanced thin film and biological applications. However, the known IE are still complicated or limited in their performance. For example, the moving ellipsometry system based on Polarizer Compensator Surface Analyzer (PCSA) components, and enabling a null ellipsometry technique, is not strong enough to measure large surfaces.