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15 November 2002 Ultrafast studies of photoexcited electronic dynamics in thiol-capped CdTe semiconductor nanoparticles
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The charge carrier dynamics of thiol-capped CdTe nanoparticles have been studied using femtosecond laser spectroscopy. High-resolution transmission electronic microscopy shows that thiol-capped CdTe particles are spherical, with 2-3 nm average diameter. Static electronic absorption spectrum suggests that they are in the strongly quantum-confined regime. Steady state emission measurements show only a band edge emission at ~ 505 nm, indicating a low density of deep-trapped states. The electronic relaxation dynamics show a fast decay (a few ps), which is dependent on excitation intensity, a slow decay (~230 ps), and an offset beyond 600 ps. The slow decay is attributed to the electron-hole recombination of surfactant or solvent trapped electrons. The intensity dependent, fast decay component is assigned to exciton-exciton annihilation or photoionization/Auger recombination, with the assistance of nanosecond fluorescence study. The decay profiles appear to be independent of probe wavelength. The overall relatively slow decay at low excitation intensity is consistent with the strong fluorescence, indicating an efficient radiative relaxation process.
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Fanxin Wu and Jin Z. Zhang "Ultrafast studies of photoexcited electronic dynamics in thiol-capped CdTe semiconductor nanoparticles", Proc. SPIE 4807, Physical Chemistry of Interfaces and Nanomaterials, (15 November 2002);

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