9/30 研究科セミナー(University College London: Prof. A. Shluger)

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MS-IV棟8階中セミナー室 15:30 - 17:00 

Mechanisms of Imaging and Manipulation of Surface Atoms using AFM

Professor Alexander Shluger 
Department of Physics and Astronomy, University College London

I will present the results of theoretical modelling of the mechanisms of atomic and chemical resolution using non-contact Atomic Force Microscopy (NC-AFM) on insulating surfaces. The chemical nature of NC-AFM tips plays the crucial role in determining contrast in images and our results show that metallic tips can provide unambiguous chemical resolution on insulating surfaces in vacuum [1]. Examples of imaging and manipulating atoms and molecules at insulating surfaces will be presented. In particular, recently it has been observed using NC-AFM that depositing organic adsorbates onto a stable ionic surface can induce structural changes of surface features, such as steps and corners [1]. This suggests that using appropriately chosen/designed molecules it should be possible to tailor the nano-scale structure of polar surfaces. However, such a control requires detailed understanding of the mechanisms and driving forces behind surface reconstructions. The atomistic model of the mechanism of the experimentally observed shape changes of nanoscale islands and pits on the nano-patterned KBr (001) surface upon the adsorption of truxene molecules functionalised with polar organic groups will be discussed. I will demonstrate how the adsorption of molecules at the edges of surface features lowers activation energies for key transitions for the shape change, enabling them to become thermally accessible. The interplay between molecular diffusion and surface reconstruction is also investigated. These calculations offer insights into designing molecules to modify and control surface features on crystal surfaces.

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