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Size-dependent electrical transport in CdSe nanocrystal thin films
Moon Sung Kang1, Ayaskanta Sahu, David J Norris
1Department of Chemical Engineering and Materials Science, University of Minnesota, 421 Washington Avenue SE, Minneapolis, Minnesota 55455, USA.
Nano Letters
|August 25, 2010
Summary
Electrical transport in cadmium selenide (CdSe) nanocrystal films depends on nanocrystal size. Larger CdSe nanocrystals exhibit higher electron mobility, with transport governed by a size-dependent hopping mechanism.
Area of Science:
- Materials Science
- Nanotechnology
- Solid State Physics
Background:
- Electrical transport in semiconductor nanocrystal films is crucial for nanoelectronic devices.
- Understanding charge carrier dynamics in these materials is key to optimizing device performance.
Purpose of the Study:
- To investigate the effect of nanocrystal size on electrical transport properties in cadmium selenide (CdSe) films.
- To elucidate the underlying mechanisms governing charge transport as a function of CdSe nanocrystal diameter.
Main Methods:
- Fabrication of CdSe nanocrystal films with controlled diameters (2.9-5.1 nm).
- Electrical transport measurements conducted over a temperature range of 233-300 K.
- Electrolyte gating used to systematically control electron density.
Main Results:
- Transport parameters showed strong, systematic variation with nanocrystal diameter.
- Device turn-on voltage correlated with the size-dependent lowest unoccupied electronic states.
- Electron mobility increased with particle diameter, reaching 0.6 cm²/Vs for 5.1 nm CdSe nanocrystals.
- Charge transport followed a nearest-neighbor-hopping model with size-dependent activation energy.
Conclusions:
- Nanocrystal size is a critical factor influencing electrical transport in CdSe films.
- The observed phenomena can be explained by a size-dependent charging energy model.
- Combined size- and temperature-dependent studies offer a robust method for understanding nanocrystal film conductivity.
