Growth and Structure of Ultrathin Iron Silicate and\nIron Germanate Films

The growth and structure\nof two-dimensional iron silicate and iron\ngermanate films on Ru(0001) are studied. We investigate in detail\nthe temperature-dependent film formation of ultrathin layers of iron\nsilicate and iron germanate. These two-dimensional films can be seen\nas model systems for more complex catalytically active structures,\nsuch as zeolites, which can be used as selective catalysts or molecular\nsieves. The experimental methods of XPS, LEED, LEEM, LEEM-IV, and\nXPEEM are applied for correlated chemical and physical characterization\nin situ and in real time, and DFT is applied for theoretical consideration.\nWe show that both systems can be considered as two-layered systems,\nwith a monolayer of iron oxide at the Ru interface and a monolayer\nof silica or germania on top, respectively. The Fe-Fe distance in\nthe iron oxide layer is influenced by the Si-O-Si or Ge-O-Ge bond\nlength, in agreement with those of unstrained silicates or germanates.\nMoreover, iron silicate can be prepared using different preparation\nmethods. The actual loading of Fe atoms is three per unit cell for\nFeGeO<sub>x</sub> and only two for FeSiO<sub>x</sub>.