Projects per year
To fully deploy the potential of semiconductor nanocrystal films as low-cost electronic materials, a better understanding of the amount of dopants required to make their conductivity metallic is needed. In bulk semiconductors, the critical concentration of electrons at the metal-insulator transition is described by the Mott criterion. Here, we theoretically derive the critical concentration nc for films of heavily doped nanocrystals devoid of ligands at their surface and in direct contact with each other. In the accompanying experiments, we investigate the conduction mechanism in films of phosphorus-doped, ligand-free silicon nanocrystals. At the largest electron concentration achieved in our samples, which is half the predicted nc, we find that the localization length of hopping electrons is close to three times the nanocrystals diameter, indicating that the film approaches the metal-insulator transition.
Bibliographical noteFunding Information:
The authors would like to thank K. A. Matveev, C. Leighton, B. Skinner and A. Kamenev for helpful discussions, C. D. Frisbie for the use of his equipment and R. Knurr for assistance with the ICP-OES analysis. T.C. (electrical transport studies) and K.V.R.(theory) were supported primarily by the National Science Foundation through the University of Minnesota MRSEC under Award Number DMR-1420013. N.J.K. (materials synthesis) was supported by the DOE Center for Advanced Solar Photophysics (CASP), an Energy Frontier Research Center funded by the U.S. Department of Energy, O_ce of Science, Basic Energy Sciences. Part of this work was carried out in the College of Science and Engineering Characterization Facility, University of Minnesota, which has received capital equipment funding from the NSF through the UMN MRSEC Program. Part of this work also used the College of Science and Engineering Nanofabrication Center, University of Minnesota, which receives partial support from NSF through the NNIN Program.
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How much support was provided by MRSEC?
Reporting period for MRSEC
- Period 2
PubMed: MeSH publication types
- Journal Article
- Research Support, Non-U.S. Gov't