AVS 58th Annual International Symposium and Exhibition
    Helium Ion Microscopy Focus Topic Wednesday Sessions
       Session HI+AS+BI+NS-WeM

Paper HI+AS+BI+NS-WeM5
He Ions Image the Au (111) Herringbone Reconstruction

Wednesday, November 2, 2011, 9:20 am, Room 106

Session: Nano- and Bio- Imaging with Helium Ion Microscopy
Presenter: Vasilisa Veligura, MESA+ Institute for Nanotechnology, University of Twente, Enschede, The Netherlands
Authors: V. Veligura, MESA+ Institute for Nanotechnology, University of Twente, Enschede, The Netherlands
G. Hlawacek, MESA+ Institute for Nanotechnology, University of Twente, Enschede, The Netherlands
R. van Gastel, MESA+ Institute for Nanotechnology, University of Twente, Enschede, The Netherlands
H. Zandvliet, MESA+ Institute for Nanotechnology, University of Twente, Enschede, The Netherlands
B. Poelsema, MESA+ Institute for Nanotechnology, University of Twente, Enschede, The Netherlands
Correspondent: Click to Email
The herringbone reconstruction of the Au(111) surface was directly visualized using an Ultra High Vacuum Helium Ion Microscope. Ion channeling phenomena arise from the different atomic ordering in the outermost layer of the crystal. First, we investigated the channeling contrast from the bulk Au fcc structure by imaging polycrystalline Au on glass films. The contrast that was observed as a function of crystal orientation was found to conform to what is calculated from a simple hard sphere model. Consequently, the herringbone reconstruction was investigated. It is a periodic zigzag structure of the three different types of crystal stacking (fcc, hcp and bridge sites connecting these regions) and, ideally, has a period of 6.3 nm. The different stacking of the atoms that constitute the surface reconstruction leads to lateral variations of the secondary electron yield that can be resolved in HIM imagery. The existence of the herringbone reconstruction on the sample was independently confirmed through STM measurements and the quantitative details from both techniques are similar, but seem to be affected by the differences in vacuum conditions. An influence of both the ion beam and vacuum environment on the visibility of the herringbone reconstruction is observed in our UHV-HIM system.