Article abstract
Nature Materials 6, 115 - 121 (2007)
Published online: 21 January 2007 | doi:10.1038/nmat1826
Subject Categories: Electronic materials | Semiconductors | Nanoscale materials
Synergism in binary nanocrystal superlattices leads to enhanced p-type conductivity in self-assembled PbTe/Ag2Te thin films
Jeffrey J. Urban1, Dmitri V. Talapin2, Elena V. Shevchenko2, Cherie R. Kagan1 & Christopher B. Murray1
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 Ag2Te, demonstrating synergistic effects leading to enhanced p-type conductivity. First, syntheses of size-tuneable PbTe and Ag2Te nanocrystals are presented, along with deposition as thin-film nanocrystal solids, whose electronic transport properties are characterized. Next, assembly of PbTe and Ag2Te nanocrystals into AB binary nanocrystal superlattices is demonstrated. Furthermore, binary composites of varying PbTe–Ag2Te stoichiometry (1:1 and 5:1) are prepared and electronically characterized. These composites show strongly enhanced (conductance 
100-fold increased in 1:1 composites over the sum of individual conductances of single-component PbTe and Ag2Te films) p-type electronic conductivity. This observation, consistent with the role of Ag2Te as a p-type dopant in bulk PbTe, demonstrates that nanocrystals can behave as dopants in nanostructured assemblies.
- I.B.M. T. J. Watson Research Center, Nanoscale Materials and Devices Group, 1101 Kitchawan Road, Yorktown Heights, New York 10598, USA
- The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
Correspondence to: Jeffrey J. Urban1 e-mail: urban@post.harvard.edu
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