Quantum Wells within Quantum Dots, a CdS/HgS Nanoheterostructure with Global and Local Confinement

Semiconductor nanocrystals prepared by methods of wet chemistry are similar to MBE grown quantum dots where the mobility of the charge carriers is reduced to zero dimensionality. In this paper we summarize the physics of a unique system in which the charge carriers are locally confined within a heterogeneous quantum dot. With high resolution electron microscopy we will show that epitaxial growth ot atomic layer precision is possible by methods of solution chemistry leading to CdS quantum dots with embedded HgS quantum wells (QDQWs). The photophysics of this system is investigated by time-correlated single photon counting, transient differential absorption and fluorescence line narrowing spectroscopies. The results reflect the very complex electronic structure of this new kind of matter which can be explained by an extended effective mass approach.