STRUCTURE IN THE LOWEST ABSORPTION FEATURE OF CDSE QUANTUM DOTS

We use transient differential absorption experiments to investigate th e ''single dot'' absorption line shape of CdSe quantum dots. We observ e both a narrow (full width half maximum similar to 5 meV) and a broad (similar to 50 meV) bleach component within the inhomogeneously broad ened first absorption line of our samples, We deduce the single dot ab sorption line shape which is most consistent with the experimental res ults. This line shape, which contains structure in the lowest quantum dot absorption feature, explains the large ''Stokes'' shift seen in th e full band edge luminescence of CdSe quantum dots. We discuss the str ucture within the context of several competing models. The data appear inconsistent with models which use surface states to explain the anom alous emission behavior of II-VI quantum dots. Instead they imply that exciton fine structure is observed in our samples. (C) 1995 American Institute of Physics.