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Ultra-thin silicate films on metal single crystals

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Yu,  Xin
Chemical Physics, Fritz Haber Institute, Max Planck Society;

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Yu, X. (2013). Ultra-thin silicate films on metal single crystals. PhD Thesis, Technische Universität, Berlin.


Cite as: https://hdl.handle.net/11858/00-001M-0000-0014-6153-1
Abstract
Silica (SiO2) is one of the most widely used and important materials in heterogeneous catalysis and other technological applications. A thin silicate film grown on metal single crystal is a suitable model system to study the electronic properties and surface chemistry of silica based materials at the atomic level using a variety of surface sensitive techniques. In this work, we studied the preparation and atomic structure of silica films on a Ru(0001) substrate. The results show that silica ca Silica (SiO2) is one of the most widely used and important materials in heterogeneous catalysis and other technological applications. A thin silicate film grown on metal single crystal is a suitable model system to study the electronic properties and surface chemistry of silica based materials at the atomic level using a variety of surface sensitive techniques. In this work, we studied the preparation and atomic structure of silica films on a Ru(0001) substrate. The results show that silica can be grown as either monolayer, which shares the structure virtually identical with SiO2.5/Mo(112), or a bilayer film. The bilayer silica film, which is weakly bound to the substrate, can be grown either as crystalline or amorphous (vitreous) depending on the preparation conditions. In addition, the film may contain interface oxygen, thus exhibiting “o-rich” and “o-poor” states. To understand the role of a metal support in the structure of the silica films, the growth of silica films on Pt(111) has been studied for comparison. The results show that the oxyfilicity (oxygen affinity to a metal) of the substrates plays a decisive role for film structure. The lattice mismatch between a film and a substrate may affect the film morphology, but to a lesser extent. The bilayer silica film on Ru(0001) has been employed as a template for preparation of metal-containing silica films, namely aluminosilicate and iron-silicate films. It is shown that the aluminosilicate films expose strongly acidic OH-species upon water adsorption. Iron-containing silica films show a close similarity to ideal nontronite (Fe-rich smectites). These films represent well-suited model systems for studying surface chemistry of zeolites and clay minerals at the atomic level