Matteo Cargnello, Stanford University
Enhanced Energy Transfer and Doping in Semiconductor-Metal Nanocrystal Superlattices
Written by Ahmad R. Kirmani
Order at the atomic scale has long inspired researchers studying matter. Apart from the many wonderful properties that colloidal nanostructures such as quantum dots (QDs) bring with them, nanocrystalline order is another. Replacing one of the atoms in these QDs leads to doping of the nanocrystals. In fact, doping has been the kingpin behind the transistor industry that ushered in the electronics revolution in the mid-20th century.
Matteo Cargnello, now an Assistant Professor at Stanford University, was interested in taking this concept to another level—doping of QD superlattices. A QD superlattice is a wonderfully ordered lattice of individual QDs. These open up the possibility of faster charge transfer through thin films owing to a significantly suppressed disorder that is, otherwise, commonplace in QD thin films. Cargnello and fellow researchers found that it is possible to replace one of the QDs in the superlattice with an appropriately-sized gold nanocluster leading to doping of the superlattice—a phenomenon not yet heard of. The researchers were able to effectively tune the conductivity of their thin films over six orders of magnitude by this “substitutional doping” approach, rightly leading the journal Nature to call this feat a “Midas touch.”