title: Synergism in binary nanocrystal superlattices leads to enhanced p-type conductivity in self-assembled PbTe/Ag2 Te thin films.
abstract: The ordered cocrystallization of nanoparticles into binary superlattices enables close contact of nanocrystals with distinct physical properties, providing a route to 'metamaterials' design. Here we present the first electronic measurements of multicomponent nanocrystal solids composed of PbTe and Ag(2)Te, demonstrating synergistic effects leading to enhanced p-type conductivity. First, syntheses of size-tuneable PbTe and Ag(2)Te nanocrystals are presented, along with deposition as thin-film nanocrystal solids, whose electronic transport properties are characterized. Next, assembly of PbTe and Ag(2)Te nanocrystals into AB binary nanocrystal superlattices is demonstrated. Furthermore, binary composites of varying PbTe-Ag(2)Te stoichiometry (1:1 and 5:1) are prepared and electronically characterized. These composites show strongly enhanced (conductance approximately 100-fold increased in 1:1 composites over the sum of individual conductances of single-component PbTe and Ag(2)Te films) p-type electronic conductivity. This observation, consistent with the role of Ag(2)Te as a p-type dopant in bulk PbTe, demonstrates that nanocrystals can behave as dopants in nanostructured assemblies.
authors.affiliation: I.B.M. T. J. Watson Research Center, Nanoscale Materials and Devices Group, 1101 Kitchawan Road, Yorktown Heights, New York 10598, USA. urban@post.harvard.edu
authors.forename: Jeffrey J
authors.initials: JJ
authors.lastname: Urban
authors.forename: Dmitri V
authors.initials: DV
authors.lastname: Talapin
authors.forename: Elena V
authors.initials: EV
authors.lastname: Shevchenko
authors.forename: Cherie R
authors.initials: CR
authors.lastname: Kagan
authors.forename: Christopher B
authors.initials: CB
authors.lastname: Murray