Ellipsometry/RAS on liquid-solid-interfaces and in-situ optics in electrochemistry.
Sprache des Vortragstitels:
Xenes-4 & Epioptics-16 International School of Solid State Physics
Sprache des Tagungstitel:
All attempts to experimentally study the microscopic properties of electrochemical or electrocatalytic reactions struggle with a fundamental problem. Thin film and surface sensitive methods, like photoemission spectroscopy, are not applicable due to the presence of the liquid surrounding. Optical or polarization optical methods are one of the remaining alternatives. In a series of studies, we and other groups have shown that in-situ ellipsometry and the related reflectance anisotropy spectroscopy (RAS) can be used to obtain information about the chemical processes, the thermodynamics, and the microscopic structure down to the atomic level at solid-liquid interfaces.
However, the outcome of such methods is rather indirect and requires a closer look in the interaction of light with the material and the specific conditions at electrified solid-liquid interfaces. We will discuss the specifics using some metal and semiconductor examples. It turned out, that it is the electron charge accumulation or depletion in connection with electronic resonances at such interfaces, which is measured optically and provides a reasonable sensitivity to related surface or film modifications. Furthermore, it is noteworthy that, unlike surfaces prepared in vacuum, electrochemical systems are usually in complete thermodynamic equilibrium. The applied electrochemical potential is here a control parameter that can be used to switch between different equilibrium states back and forth.
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 S. Vazquez-Miranda, et al., J. Phys. Chem. C 124, 5204 (2020).
 M.-H. Chien, et al., J. Phys. Chem. C 122, 8984 (2018).
 1 C. Cobet, et al., J. Phys. Chem. C 122, 24309 (2018).
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Hauptvortrag / Eingeladener Vortrag auf einer Tagung