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Rev Sci Instrum ; 87(11): 113705, 2016 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-27910601


We have developed a new instrument combining a scanning probe microscope (SPM) and an X-ray scattering platform for ambient-pressure catalysis studies. The two instruments are integrated with a flow reactor and an ultra-high vacuum system that can be mounted easily on the diffractometer at a synchrotron end station. This makes it possible to perform SPM and X-ray scattering experiments in the same instrument under identical conditions that are relevant for catalysis.

Nat Commun ; 7: 10733, 2016 Feb 18.
Artigo em Inglês | MEDLINE | ID: mdl-26888311


Vapour deposition on polycrystalline films can lead to extremely high levels of compressive stress, exceeding even the yield strength of the films. A significant part of this stress has a reversible nature: it disappears when the deposition is stopped and re-emerges on resumption. Although the debate on the underlying mechanism still continues, insertion of atoms into grain boundaries seems to be the most likely one. However, the required driving force has not been identified. To address the problem we analyse, here, the entire film system using thermodynamic arguments. We find that the observed, tremendous stress levels can be explained by the flux-induced entropic effects in the extremely dilute adatom gas on the surface. Our analysis justifies any adatom incorporation model, as it delivers the underlying thermodynamic driving force. Counterintuitively, we also show that the stress levels decrease, if the barrier(s) for adatoms to reach the grain boundaries are decreased.

J Phys Condens Matter ; 22(26): 264007, 2010 Jul 07.
Artigo em Inglês | MEDLINE | ID: mdl-21386464


The time resolution of a conventional scanning tunneling microscope can be improved by many orders of magnitude by recording open feedback loop current-time traces. The enhanced time resolution comes, however, at the expense of the ability to obtain spatial information. In this paper, we first consider the Ge(111)-c(2 × 8) surface as an example of how surface dynamics can show up in conventional STM images. After a brief introduction to the time-resolved scanning tunneling microscopy technique, its capabilities will be demonstrated by addressing the dynamics of a dimer pair of a Pt modified Ge(001).

Germânio/química , Microscopia de Tunelamento/instrumentação , Platina/química , Semicondutores , Simulação por Computador , Cinética , Microscopia de Tunelamento/métodos , Propriedades de Superfície , Fatores de Tempo
Nano Lett ; 9(5): 1733-6, 2009 May.
Artigo em Inglês | MEDLINE | ID: mdl-18781806


We demonstrate the feasibility of controlling an atomic scale mechanical device by an external electrical signal. On a germanium substrate, a switching motion of pairs of atoms is induced by electrons that are directly injected into the atoms with a scanning tunneling microscope tip. By precisely controlling the tip current and distance we make two atom pairs behave like the flippers of an atomic-sized pinball machine. This atomic scale mechanical device exhibits six different configurations.