Among the many available real-time characterization methods, ellipsometry stands out with the combination of high sensitivity and high speed as well as nondestructive, spectroscopic, and complex modeling capabilities. The thicknesses of thin films such as the complex dielectric function can be determined simultaneously with precisions down to sub-nanometer and 10–4, respectively. Consequently, the first applications of high- and low-temperature real-time ellipsometry have been related to the monitoring of layer growth and the determination of optical properties of metals, semiconductors, and superconductors, dating back to the late 1960s. Ellipsometry has been ever since a steady alternative of nonpolarimetric spectroscopies in applications where quantitative information (e.g., thickness, crystallinity, porosity, band gap, absorption) is to be determined in complex layered structures. In this article the main applications and fields of research are reviewed.

The effect of laser irradiation in the energy range from 20 mW to 200 mW was investigated in 109 nm thick Fe51Rh49 film deposited on an MgO (100) substrate. The initial, A1 structure with fully paramagnetic magnetic ordering was achieved after irradiating the samples with 120 keV Ne+ ions with a fluence of 1 × 1016 ion/cm2, as it was confirmed by conversion-electron Mössbauer spectroscopy. At higher powers physical damage of the layer was observed, while in the lowest power case, magnetic force microscopy revealed a well-defined magnetic structure reflecting the laser irradiation pattern. The presented results have the potential to be employed for laser ablation or allows the fabrication of arbitrary ferromagnetic pattern within a homogeneous paramagnetic FeRh thin films.

Spectroscopic ellipsometry is a sensitive and optical model-supported quantitative tool to monitor interfaces. In this work, solid-liquid interfaces are studied using the Kretschmann-Raether configuration for biosensing applications. The interface layers support two purposes simultaneously: (i) chemical suitability for the adsorption of molecules to be detected and (ii) the optical enhancement of the signal to increase the sensitivity. Ellipsometry is not only used as a sensor but also as a quantitative measurement tool to study and understand the interface phenomena, and to develop the sensing layers for the largest possible optical sensitivity. Plasmonic and structured layers are of primary importance in terms of optical sensitivity. Layers structured both in lateral and vertical directions have been studied. Optical models based on both the transfer matrix and the finite element method were developed and used for the structural analysis where the material and geometrical derivatives are used in the inverse fitting process of the model data to the measurement. Structures utilizing plasmonic, diffraction, multilayer field enhancement, and other methods were analyzed as possible candidates for the improvement of the optical performance of the cell. Combinatorial and periodic plasmonic surface structures were developed to enhance the sensitivity of in-situ ellipsometry at solid-liquid interfaces utilizing the Kretschmann-Raether (KR) geometry. Ag x Al 1−x layers with variable compositions and Au layers with changing periods and critical dimensions were investigated to improve the performance of sensors based on the KR arrangement.