Tight-Binding Theory of ZnS/CdS Nanoheterostructures: The Role of Strain and d Orbitals

Published

October 12, 2021

Author(s)

J G. Diaz, M Zielinski, W Jaskolski, Garnett W. Bryant

Abstract

The electronic and optical properties of colloidal multi-shell ZnS/CdS nanoheterostructures have been studied in the framework of empirical tight-binding models. Our approach takes into account the effects of the strain caused by the large lattice mismatch at the interface between the two materials. We show that the inclusion of d orbitals into a minimal basis set is necessary to provide a correct description of the ZnS and CdS clads that are only a few monolayers thick. The role of strain is also important. Strain shifts of the electron energy levels are highly dependent on the thickness of the core and shell materials. The effects of strain in the valence band are more complex. In CdS/ZnS structures, strain can change the symmetry of the ground hole state. In ZnS/CdS systems, strain lowers the energy of the ground hole state of P-symmetry with respect to the first S-symmetry state, enhancing theStokes shift. Lattice relaxation also redistributes the charge densities of electron and hole states. The predicted absorption onsets resulting from our model are in good agreement with the experimental data and in better agreement with data than previous theories without strain and d orbitals.

Citation

Physical Review B (Condensed Matter and Materials Physics)

Pub Type

Journals

Keywords

electronic structure, nanocrystal, quantum dot, strain

Citation

Diaz, J. , Zielinski, M. , Jaskolski, W. and Bryant, G. (2021), Tight-Binding Theory of ZnS/CdS Nanoheterostructures: The Role of Strain and d Orbitals, Physical Review B (Condensed Matter and Materials Physics) (Accessed April 25, 2024)