First-Principles Calculations of Nanoplatelet Heterostructures: Surface Ligands and Strain Fields

ORAL

Abstract

Nanoplatelets (NPLs) – highly anisotropic, quasi-two-dimensional semiconductor nanostructures – exhibit optoelectronic properties that are governed by their precisely tunable thickness of a few atomic layers. However, the atomistic structure of NPLs is not completely known and is expected to depend on the passivating ligands. Here we determine the structure of both CdSe-core and CdSe/CdS-core/shell NPLs, using Density Functional Theory (DFT) and the Qbox code[1]. For both core and core/shell NPLs with different thicknesses and ligands, we determined the equilibrium positions and the in-plane strain. We found that NPL thickness, different ligands and the presence of a shell are all factors affecting the axial atomistic structure and they are responsible for inducing an in-plane strain field, which in many studies has been neglected. We show that, compared to CdSe NPL of the same thickness, the lattice constants of the core-shell NPLs expand in the axial direction, in agreement with recent experiments[2]. We rationalize our first principles findings by a continuum elastic model including surface-stress terms that account for the surface passivation of NPLs.

[1] Gygi F, IBM J. Res. Dev. 52.1.2 (2008): 137-144.
[2] Hazarika et al. Submitted.

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Presenters

  • Sergio Mazzotti

    Optical Materials Engineering Laboratory, Department of Mechanical and Process Engineering, ETH Zurich

Authors

  • Sergio Mazzotti

    Optical Materials Engineering Laboratory, Department of Mechanical and Process Engineering, ETH Zurich

  • Arin R Greenwood

    Institute for Molecular Engineering, University of Chicago

  • David J Norris

    Optical Materials Engineering Laboratory, Department of Mechanical and Process Engineering, ETH Zurich

  • Giulia Galli

    Institute for Molecular Engineering, University of Chicago, Institute for Molecular Engineering and Materials Science Division, University of Chicago and Argonne National Laboratory, University of Chicago, Argonne National Lab, Institute for Molecular Engineering and Department of Chemistry, University of Chicago, University of Chicago and Argonne National Laboratory, The Institute for Molecular Engineering, University of Chicago, University of Chicago, Institute for Molecular Engineering, Univ. of Chicago; Department of Chemistry, Univ. of Chicago; Materials Science Division, Argonne National Laboratory