Regensburg 2019 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 6: Water on Surfaces

O 6.5: Vortrag

Montag, 1. April 2019, 11:45–12:00, H16

Towards Reality: Interaction of Magnetite Fe₃O₄(001) with Liquid and Ambient Pressure Water — •francesca mirabella, florian kraushofer, matthias müllner, jian xu, jiri pavelec, jan balajka, michael schmid, ulrike diebold, and gareth parkinson — Technische Universität Wien, Vienna, Austria

Water interaction with iron oxides plays an important role in different fields. The structure of the solid-liquid interface often defines the performance of a material in its applications. As a first step, we studied the stability of a UHV-prepared Fe3O4(001)-(√2×√2)R45^∘ surface upon interaction with water vapor as well as liquid. We used a new experimental setup that allows to bring a UHV-prepared surface in direct contact with ultrapure liquid water (and vapor) without exposure to air. The effect of water on the surface was then studied with low energy electron diffraction (LEED), X-ray photoemission spectroscopy (XPS) and scanning tunneling microscopy (STM). XPS data show that the surface is hydroxylated upon short exposure (seconds) to ultra-pure liquid H2O. After longer exposure (minutes-hour), STM shows new features, namely rows growing on top of the pristine surface. The growth of these rows is accompanied by a stronger hydroxylation of the surface (XPS) and lifting of the (√2×√2)R45^∘ reconstruction (LEED). XPS data, several control experiments, and reproducibility in two different UHV chambers let us exclude any contamination. The formation of these rows seems to be restricted to the surface layer. We interpret them as iron-(oxy)-hydroxide species formed by excess iron diffusing out from subsurface layers in a kinetically-limited process.