Dresden 2014 – scientific programme
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O: Fachverband Oberflächenphysik
O 36: Posters: Bio/organic Molecules on Surfaces, Graphene, Solid/liquid interfaces, Metal Substrates, Electronic Structure Theory
O 36.79: Poster
Tuesday, April 1, 2014, 18:30–22:00, P1
Adsorbate nanomesh causes lateral periodicity of segregation: Ab-initio study for h-BN on Pt50Rh50(111) — •Wolfgang Heckel1, Tobias C. Kerscher1, Roland Stania2, Irakli Kalichava3, Juerg Osterwalder2, Phil Willmott3, Bernd Schönfeld4, Thomas Greber2, and Stefan Müller1 — 1Hamburg University of Technology, Institute of Advanced Ceramics — 2Universität Zürich, Physik-Institut — 3Paul Scherrer Institut Villigen, Swiss Light Source — 4ETH Zürich, LMPT
The segregation profile of Pt–Rh surfaces strongly depends on the presence of adsorbates; e.g., at the top layer, the clean surface favors Pt enrichment, yet a small amount of C adsorbates leads to a significant depletion of Pt there [1]. Pt–Rh also serves as a substrate for self-assembled 2d adsorbate layers such as boron nitride (h-BN). The experiments on h-BN/Pt50Rh50(111) show a corrugated, honeycombed 11×11 nanomesh adsorbate layer caused by the lattice constant mismatch of substrate and adsorbate. We present an ab-initio study combining DFT data and a cluster–expansion approach with UNCLE [2]. We elucidate the laterally periodic segregation profile of Pt50Rh50(111) caused by h-BN. Our results perfectly confirm the experiment: Beneath the pores of the nanomesh the segregation profile shows a strong Rh enrichment, while beneath the wires the topmost layer favors platinum. By this, the h-BN layer induces a segregation profile with a lateral periodicity according to its honeycombed nanomesh.
[1] Kerscher et al., Phys. Rev. B 86, 195420 (2012)
[2] Lerch et al., Modelling Simul. Mater. Sci. Eng. 17, 055003 (2009)