title: Visualization of steps and surface reconstructions in Helium Ion Microscopy with atomic precision.
abstract: Helium Ion Microscopy is known for its surface sensitivity and high lateral resolution. Here, we present results of a Helium Ion Microscopy based investigation of a surface confined alloy of Ag on Pt(111). Based on a change of the work function of 25meV across the atomically flat terraces we can distinguish Pt rich from Pt poor areas and visualize the single atomic layer high steps between the terraces. Furthermore, dechanneling contrast has been utilized to measure the periodicity of the hcp/fcc pattern formed in the 2-3 layers thick Ag/Pt alloy film. A periodicity of 6.65nm along the ⟨112⟩ surface direction has been measured. In terms of crystallography a hcp domain is obtained through a lateral displacement of a part of the outermost layer by 1/√3 of a nearest neighbor spacing along ⟨112⟩. This periodicity is measured with atomic precision: coincidence between the Ag and the Pt lattices is observed for 23 Ag atoms on 24 Pt atoms. The findings are perfectly in line with results obtained with Low Energy Electron Microscopy and Phase Contrast Atomic Force Microscopy.
authors.affiliation: Physics of Interfaces and Nanomaterials, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands. Electronic address: g.hlawacek@hzdr.de.
authors.forename: Gregor
authors.initials: G
authors.lastname: Hlawacek
authors.affiliation: Physics of Interfaces and Nanomaterials, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands.
authors.forename: Maciej
authors.initials: M
authors.lastname: Jankowski
authors.affiliation: Physics of Interfaces and Nanomaterials, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands.
authors.forename: Herbert
authors.initials: H
authors.lastname: Wormeester
authors.affiliation: Physics of Interfaces and Nanomaterials, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands.
authors.forename: Raoul
authors.initials: R
authors.lastname: van Gastel
authors.affiliation: Physics of Interfaces and Nanomaterials, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands.
authors.forename: Harold J W
authors.initials: HJW
authors.lastname: Zandvliet
authors.affiliation: Physics of Interfaces and Nanomaterials, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands.
authors.forename: Bene
authors.initials: B
authors.lastname: Poelsema
keywords: Channeling; Helium Ion Microscopy; Low Energy Electron Microscopy; Step contrast; Surface alloy