Röntgenstreuexperimente zur Aufklärung der Struktur von Flüssigkeiten und Quasiflüssigkeiten in Kontakt mit Festkörpern

• Applicant: Professor Dr. Helmut Dosch
• Subject Area: Experimental Condensed Matter Physics
• Term: from 1998 to 2005
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 5221630

It is expected that the local structure of a liquid in contact with a solid is crucially altered at the interface. Modern theories predict a layering perpendicular to the interface within a width given by the correlation length of the liquid. In addition to that an in-plane modulation of the liquid factor is expected by the periodic substrate potential of the solid. This results in a modification of the measured x-ray signals from the interface as compared to the signals from a pure bulk liquid. In order to provide the necessary interface sensitivity we have developed a new scattering geometry using high energy photons (E = 70keV). The idea is to create an evanescent wave field inside the liquid adjacent to the interface. Experimentally this can be achieved by using the effect of total internal reflection. The implanted evanescent wave is then scattered from solid-modulated liquid density fluctuations.Our experiments at the solid-liquid interface Si(001)-Pb(liq.) have shown that this method is indeed well suited for the investigation of deeply buried liquid interfaces. First measurements of the in-plane liquid structure factor at the interface display modifications in the measured structure factor compared to the bulk liquid structur factor, indicated by amplitude modulations of the various correlation maxima as a function of the in-plane orientation of the solid substrate. The future investigations will focus on the interfacial liquid structure factor as a function of various parameters as the temperature of the interface or the orientation and morphology of the solid surface.

• DFG Programme: Priority Programmes
• Subproject of: SPP 1052: Benetzung und Strukturbildung an Grenzflächen