Interplay of Coulomb, exchange, and spin-orbit effects in semiconductor nanocrystallites

Size-selective spectroscopic techniques and a tight-binding calculation with restricted configuration interaction have been used to study the relative effects of Coulomb, exchange, and spin-orbit coupling terms on the size dependence of the lowest optical transitions in CdS nanocrystallites. Quantitative agreement is obtained for the magnitude of the corresponding dominant transitions. The nature of the states is analyzed on the basis of a simple model. A brief comparison to other semiconductor nanocrystallites like CdSe is finally presented.