Realization of an atomic sieve: Silica on Mo(1 1 2)
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- 作者：Stefan Ulrich ; Niklas Nilius ; Hans-Joachim Freund ; Umberto Martinez ; Livia Giordano ; Gianfranco Pacchioni
- 关键词：Adsorption ; Oxide surfaces ; Scanning tunneling microscopy ; Density functional theory
- 刊名：Surface Science
- 出版年：2009
- 出版时间：15 April 2009
- 年：2009
- 卷：603
- 期：8
- 页码：1145-1149
- 全文大小：1541 K
文摘
The adsorption of Pd, Ag and Au atoms on a porous silica film on Mo(1 1 2) is investigated by scanning tunneling microscopy and density functional theory. While Pd atoms are able to penetrate the holes in the silica top-layer with virtually no barrier, Ag atoms experience an intermediate barrier value and Au atoms are completely unable to pass the oxide surface. The penetration probability does not correlate with the effective size of the atoms, but depends on their electronic structure. Whereas Pd with an unoccupied valence s-orbital has a low penetration barrier, Ag and Au atoms with occupied s-states experience a substantial repulsion with the filled oxide states, leading to a higher barrier for penetration. In the case of Ag, the barrier height can be temporally lowered by promoting the Ag 5s-electron into the support. The Mo-supported silica film can thus be considered as a primitive form of an atomic sieve whose selectivity is controlled by the electronic structure of the adatoms.