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Photoconductivity of Langmuir-Blodgett monolayers of silicon nanoparticles

Pradhan, Sulolit and Chen, Shaowei and Zou, Jing and Kauzlarich, Susan M. (2008) Photoconductivity of Langmuir-Blodgett monolayers of silicon nanoparticles. JOURNAL OF PHYSICAL CHEMISTRY C, 112 (34). pp. 13292-13298.

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Official URL: http://pubs.acs.org/doi/abs/10.1021/jp8044719

Abstract

The electronic conductivity of Langmuir-Blodgett monolayers of silane-passivated silicon nanoparticles (core diameter 3.86 +/- 0.85 nm) was examined by electrochemical measurements within the context of photoirradiation and at controlled temperatures. Temperature dependence of the dark conductivity indicated that the interparticle charge transfer followed a thermal activation mechanism within the temperature range of 200-320 K; whereas at lower temperature, the ensemble conductance was determined by tunneling between (clusters of) nanoparticles that were of equivalent energy states. When exposed to photoexcitation with photon energy greater than the effective particle bandgap, the particle ensemble conductivity exhibited a drastic enhancement as compared to that in the darks and, at a specific excitation wavelength, the conductivity became virtually independent of temperature. This suggested efficient ionization of the photoexcited quantum-confined electron-hole pairs by the applied electric field, most probably because of the relatively slow (radiative and nonradiative) recombination dynamics. Furthermore, whereas the photoconductivity increased with increasing photon energy in photoirradiation, the enhancement diminished gradually with increasing temperature, as a consequence of the combined effects of enhanced radiative and nonradiative recombination rate and increasing contribution from thermally activated interparticle charge transfer.

Item Type:Article
Subjects:Physical Science > Nanoelectronics
Physical Science > Photonics
ID Code:1431
Deposited By:Farnush Anwar
Deposited On:12 Dec 2008 15:42
Last Modified:12 Dec 2008 15:42

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