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09/22/2017

Mapping the Atomistic Structure of Colloidal Nanocrystals

Two research teams from the Laboratory for Nanoelectronics (ETH Zurich) and the Institute of Physics (MU Leoben) revealed the atomistic structure and shape of graded core/shell nanocrystals.

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These were only possible by combining several complementary x-ray and electron microscopy techniques. These results were published in a Journal of the Nature publishing group in Scientific Reports:

Mapping the Atomistic Structure of Graded Core/Shell Colloidal Nanocrystals
Maksym Yarema , Yunhua Xing, Rainer T. Lechner, Lukas Ludescher, Nikola Dordevic, Weyde M. M. Lin, Olesya Yarema & Vanessa Wood, Sci. Rep. 7, 11781 (2017)

 

Abstract:

Engineering the compositional gradient for core/shell semiconductor nanocrystals improves their optical properties. To date, however, the structure of graded core/shell nanocrystal emitters has only been qualitatively described. In this paper, we demonstrate an approach to quantify nanocrystal structure, selecting graded Ag-In-Se/ZnSe core/shell nanocrystals as a proof-of-concept material. A combination of multi-energy small-angle X-ray scattering and electron microscopy techniques enables us to establish the radial distribution of ZnSe with sub-nanometer resolution. Using ab initio shape-retrieval analysis of X-ray scattering spectra, we further determine the average shape of nanocrystals. These results allow us to generate three-dimensional, atomistic reconstructions of graded core/shell nanocrystals. We use these reconstructions to calculate solid-state Zn diffusion in the Ag-In-Se nanocrystals and the lattice mismatch between nanocrystal monolayers. Finally, we apply these findings to propose design rules for optimal shell structure and record-luminescent core/shell nanocrystals.

Link: https://www.nature.com/articles/s41598-017-11996-2

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