Electron energy levels in ZnSe quantum dots

The size dependence of electron energy levels of ZnSe quantum dots were studied by size selective photoluminescence excitation spectroscopy at low temperature. ZnSe quantum dots of different sizes were synthesized by a high temperature wet chemical route. Cubic zinc-blende crystallites with sizes ranging from 1.5 to 4.5 nm showing only band edge luminescence were obtained. Four excited state transitions have been observed in photoluminescence excitation spectroscopy. This study establishes a connection between the electron energy levels of ZnSe quantum dots and their corresponding size. The experimentally observed excited states for ZnSe quantum dots have been analyzed on the basis of "effective mass approximation" calculations. The observed transitions for wide band gap ZnSe are compared with the well studied material, viz., CdSe. The present work enables one to gain further insight into the size dependence of the electronic structure of semiconductor quantum dots. (c) 2006 American Institute of Physics.