Thermodynamic instability of ZnSe/ZnS core/shell quantum dots

Abstract

We investigate the stability of ZnSe/ZnS core/shell quantum dots (QDs) based on density-functional-theory (DFT) calculations combined with photoluminescence (PL) and x-ray photoelectron (XPS) spectroscopy of as-synthesized and annealed QDs. The results demonstrate that core/shell interfaces in ZnSe/ZnS QDs are thermodynamically unstable. Under low-temperature annealing, the intermixing of S and Se atoms leads to alloying of the pure ZnSe core and ZnS shells. Upon high-temperature annealing, the degradation of the PL properties of the QDs also is observed. © 2012 American Institute of Physics.