Berlin 2018 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 30: Interfaces

MM 30.5: Talk

Wednesday, March 14, 2018, 11:15–11:30, H 0107

Ab-initio based study of topological segregation of C impurities at Si grain boundaries — •Masud Alam, Liverios Lymperakis, Christain Liebscher, and Jörg Neugebauer — Max-Planck Institute for Iron Research,Max-Planck Str.1 , 40237 Duesseldorf, Germany

Interfaces significantly influence the properties of multi-crystalline Si. More specifically, they introduce states in the fundamental band gap thereby allowing preferential impurities segregation and/or the formation of stable or metastable equilibrium interface phases. In the present work we investigate the segregation of C impurities at flat and faceted Si Grain Boundaries (GBs). In a first step we employ density functional theory (DFT) calculations to parametrize Si, C and Si-C modified embedded atom method (MEAM) interatomic potentials. Careful benchmarks show that the potentials provide an accurate description of the atomic geometry and energetics of intrinsic Si GBs (Wulff diagram) as well as of the C segregation at the aforementioned interfaces. Based on the new potential, we identify the preferential carbon segregation at faceted GBs. Using this insight we are able to interpret recent experimental findings on the topological segregation of impurities at facet junctions. More specifically, the presence of the energetically favorable non symmetric Σ 3 112 GB results in strong anisotropy of the strain field and hence in strong selectivity of C impurities at the GB junctions.