E-Book Overview
The investigation of the interfacial phase transitions in fluid systems with short-range intermetallic interactions are of great interest. The phenomena were studied in two systems exhibiting a liquid-liquid miscibility gap: at the fluid/wall interface in fluid KxKCl1-x and at the fluid/vacuum interface of the Ga1 xBix alloys. To characterize the interfacial changes of the ultra thin films (composition, thickness and their evolution with time) the spectroscopic ellipsometry was performed over a wide spectral range. Whereas in the experiments on KxKCl1-x an existing ellipsometer could be used, a completely new UHV-apparatus including the in-situ phase modulation ellipsometer had to be developed for Ga1 xBix alloys. For the KxKCl1-x system new results on complete wetting at solid-liquid coexistence as well as in the homogenous liquid phase (prewetting) are presented. The spectra show the typical F center absorption which indicates that the film is a salt-rich phase. The thickness strongly increases approaching the monotectic from 30 to 440 nm, which is in agreement with the tetra point wetting scenario. For this interpretation a quantitative description of the excess Gibbs energy has been developed. For the Ga1 xBix system the results on complete wetting, surface freezing and oscillatory interfacial instabilities are presented. The high-precision spectra have been recorded approaching the liquid-liquid miscibility. These spectra have been modeled using a Ga-Bi effective medium approximation for the substrate covered by a film of liquid Bi. The measurements give evidence of tetra point wetting in the Ga-Bi system. First ellipsometric study of the surface freezing in Ga-Bi has been performed. Within the miscibility gap a very interesting effect of surface and bulk oscillatory instability was observed. The details of this process at present are not well understood, but a qualitative description is given.
E-Book Content
Stanislav Dogel
Spectroscopic Ellipsometry of Interfacial Phase Transitions in Fluid Metallic Systems: Kx(KCl)1-x and Ga1-xBix
ISBN 3-937300-08-2
universitätsverlag karlsruhe
Dissertation, Universität Karlsruhe (TH), 2004
Impressum Universitätsverlag Karlsruhe c/o Universitätsbibliothek Straße am Forum 2 D-76131 Karlsruhe www.uvka.de Alle Rechte vorbehalten Universitätsverlag Karlsruhe 2004
ISBN 3-937300-08-2
Content: Zusammenfassung /Abstract..……………………………………………………………...
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1. Introduction……………………………………………………………………………...
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2. Interfacial phenomena…………………………………………………………………..
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2.1 Classification of wetting transitions, surface freezing and interfacial instabilities…………………………………………………………………….
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2.2 Theoretical concepts of the effective interfacial potential…………………….
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2.3 Long and short-range interactions - thickness of wetting layer……………….
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2.4 Overview of experimental and theoretical results on K-KCl and Ga-Bi surface transition studies………………………………………………………
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3. Characterization of surfaces and interfaces by spectroscopic ellipsometry ……….…..
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3.1 Interaction of light with matter………………………………………………..
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• Dielectric function and complex index of refraction………………….…
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• Drude and Lorentz-oscillator models……………………………………
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3.2 Spectroscopic ellipsometry……………………………………………………
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• Basic definitions and principal setup………………………………….…
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• Rotating analyser ellipsometer (RA)……………………………………
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• Phase modulation ellipsometry………………………………………….
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3.3 Simple models of the optical interfacial characteristics………………………
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• 2 phase model……………………………………………………………
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• 3