The effect of spatial distribution of Zn vacancies in ZnS quantum dots on optical absorption spectra

In this work we propose how to identify the location and spatial distribution of Zn vacancies in ZnS quantum dots (QDs). The experiments reveal a peak shift in absorption spectra towards the lower energies (about 0.1 eV) in the presence of Zn vacancies. To explain such a shift we computationally study the absorption spectra when Zn vacancies are localized in the core, on the surface, and both in the core and on the surface of a quantum dot. From the comparison with the experimental data we conclude that the most favorable configuration of the vacancies is an aggregation on a QD surface. We find that Zn vacancies localized in the core or uniformly distributed on the QD surface, do not explain the experimentally observed shift in the absorption curves.