Surface Reconstructions in II-VI Quantum Dots

Surface Reconstructions in II-VI Quantum Dots

Llusar, Jordi (Basque Center for Materials, Applications and Nanostructures (BCMaterials))
du Fossé, I. (TU Delft ChemE/Opto-electronic Materials)
Hens, Zeger (Universiteit Gent)
Houtepen, A.J. (TU Delft ChemE/Opto-electronic Materials)
Infante, Ivan (Basque Foundation for Science)

2023

Although density functional theory (DFT) calculations have been crucial in our understanding of colloidal quantum dots (QDs), simulations are commonly carried out on QD models that are significantly smaller than those generally found experimentally. While smaller models allow for efficient study of local surface configurations, increasing the size of the QD model will increase the size or number of facets, which can in turn influence the energetics and characteristics of trap formation. Moreover, core-shell structures can only be studied with QD models that are large enough to accommodate the different layers with the correct thickness. Here, we use DFT calculations to study the electronic properties of QDs as a function of size, up to a diameter of ∼4.5 nm. We show that increasing the size of QD models traditionally used in DFT studies leads to a disappearance of the band gap and localization of the HOMO and LUMO levels on facet-specific regions of the QD surface. We attribute this to the lateral coupling of surface orbitals and the formation of surface bands. The introduction of surface vacancies and their a posteriori refilling with Z-type ligands leads to surface reconstructions that widen the band gap and delocalize both the HOMO and LUMO. These results show that the surface geometry of the facets plays a pivotal role in defining the electronic properties of the QD.

density functional theory
quantum dots
semiconductors
surface reconstructions
surface states

http://resolver.tudelft.nl/uuid:b650b152-1ecf-41b9-99e2-ae0b94d2e58f

https://doi.org/10.1021/acsnano.3c09265

1936-0851

ACS Nano (online), 18 (2), 1563-1572

Institutional Repository

journal article

© 2023 Jordi Llusar, I. du Fossé, Zeger Hens, A.J. Houtepen, Ivan Infante