Single Magnetic Impurities in Colloidal Quantum Dots and Magic-Size Clusters

Impurity doping can be used to dramatically alter the physical properties of semiconductor nanostructures and endow them with promising new technological potential. This review summarizes recent progress toward the development of colloidal semiconductor quantum dots (QDs) doped with individual magnetic impurity ions. Such singly doped quantum dots (SDQDs), as well as related magic-sized nanoclusters, represent an exciting class of materials for cultivating unique physical effects arising from magnetic exchange coupling between delocalized charge carriers and the single impurity ions. Key exchange effects can be enhanced by carrier confinement in such small structures. The physical properties displayed by these materials may prove valuable for new technologies based on the manipulation of individual spins in semiconductor nanostructures, such as spintronics, spin-photonics, or quantum computing. Interesting chemical and analytical challenges also emerge when exploring this research frontier. Here, we describe cluster and QD results from recent literature related to these challenges. We summarize (magneto-)optical investigations of SDQDs on both the ensemble and single-particle levels. Comparisons to analogous bulk materials and self-assembled QDs are drawn and used to highlight some of the rich and unique characteristics found within this class of materials.