Nanocrystals used as dopants
Nanocrystals can mimic atoms in solid-state devices by altering the electrical properties — for example conductance — according to a report by Jeffrey Urban and colleagues in the February issue of Nature Materials.The researchers investigated the electrical properties of films obtained by the aggregation of PbTe and Ag2Te nanocrystals. When comparing the conductivity of films with different proportions of the two constituents, they found that when both types of crystals were present, the conductivity could be up to three orders of magnitude higher than in either of the single-component cases.Nanocrystal assemblies can be seen as materials in which the nanocrystals — which consist of thousands of atoms — act as the basic elements, with the advantage that the structure can be designed very precisely. The extension of the nanocrystal–atom analogy to the concept of doping (adding an impurity to alter the electrical properties) opens unexpected opportunities for the design of solid-state devices based on these aggregates, as it also allows very accurate control of the electrical properties.Author contact:Jeffrey J. Urban (IBM TJ Watson Research Center, Yorktown Heights, New York, USA)Tel: +1 914 945 1436; E-mail: urban@post.harvard.edu