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O: Fachverband Oberflächenphysik
O 97: Nanostructure at Surfaces: Structures and Properties
O 97.4: Vortrag
Freitag, 20. März 2015, 11:15–11:30, MA 005
Mechanical properties of surfaces at the nanoscale — •Jörg Buchwald1 and Stefan G. Mayr1,2,3 — 1Leibniz Institute of Surface Modification, Permoserstr. 15, 04318 Leipzig, Germany — 2Faculty of Physics and Earth Sciences, University of Leipzig, Linnéstr. 5, 04103 Leipzig, Germany — 3Translational Center for Regenerative Medicine (TRM)Leipzig, Philipp-Rosenthal-Str. 55, 04103 Leipzig, Germany
New experimental techniques like contact resonance atomic force microscopy (CR-AFM) allow for non-destructive testing mechanical properties with nanometer resolution. Mechanical properties of surfaces or nanostructures deviate from bulk material due to surface stresses as well as local relaxations. In experimental indentation based measurements discrimination between physical effects and artifacts - primarily due to variation of indenter contact area and extend of stress field - poses the largest challenge. To calculate the surface sensitivity of the indentation moduli, we performed a computational multiscale approach to study the phenomena on different scales. We utilized ab-initio-DFT and molecular dynamics to simulate the mechanical properties, i. e. the surface elastic constants of Si and SrTiO3 ultra-thin films. These results were used to build up a finite-element layer model where the influence of surface stresses in indentation experiments is studied. Additionally, we propose an analytical model that describes the decrease in the moduli due to surface stresses as a function of the contact radius.