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Nat Mater. 2018 Feb;17(2):152-158. doi: 10.1038/nmat5048. Epub 2017 Dec 11.

Isotope engineering of van der Waals interactions in hexagonal boron nitride.

Author information

1
Laboratoire Charles Coulomb (L2C), Université de Montpellier, CNRS, 34095 Montpellier, France.
2
Department of Chemical Engineering, Kansas State University, Manhattan, Kansas 66506, USA.
3
Institut Européen des Membranes, UMR 5635 CNRS-Univ. Montpellier-ENSCM, 34095 Montpellier, France.
4
Institut Jaume Almera, Consejo Superior de Investigaciones Científicas (ICTJA-CSIC), 08028 Barcelona, Spain.

Abstract

Hexagonal boron nitride is a model lamellar compound where weak, non-local van der Waals interactions ensure the vertical stacking of two-dimensional honeycomb lattices made of strongly bound boron and nitrogen atoms. We study the isotope engineering of lamellar compounds by synthesizing hexagonal boron nitride crystals with nearly pure boron isotopes (10B and 11B) compared to those with the natural distribution of boron (20 at% 10B and 80 at% 11B). On the one hand, as with standard semiconductors, both the phonon energy and electronic bandgap varied with the boron isotope mass, the latter due to the quantum effect of zero-point renormalization. On the other hand, temperature-dependent experiments focusing on the shear and breathing motions of adjacent layers revealed the specificity of isotope engineering in a layered material, with a modification of the van der Waals interactions upon isotope purification. The electron density distribution is more diffuse between adjacent layers in 10BN than in 11BN crystals. Our results open perspectives in understanding and controlling van der Waals bonding in layered materials.

PMID:
29251722
DOI:
10.1038/nmat5048

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