Picosecond electronic relaxation in 3-layered CdS-HgS-CdS semiconductor nanoparticles
- Georgia Institute of Technology, Atlanta, GA (United States); and others
Nanoparticles of CdS capped with a monolayer shell of CdS and an outer monolayer shell of CdS give quantum dot-quantum well (QDQW) particles. We have monitored the temporal behavior of the broad spectral hole (due to absorption bleaching) burned in their absorption spectra with a femtosecond laser at different wavelengths at 10 K. The location and the width of the initial hole are excitation dependent. As a function of delay time, the broad transient bleaching band decays to give a more narrow band with a maximum near 1.9 eV. This final narrow band is observed independently of excitation wavelength and is assigned to excitonic trapping within the HgS well. The rate of trapping is found to depend on the excitation wavelength. UV excitation creates high energy electron-hole pair which is trapped by the well in 2 ps. Within the well, the exciton relaxes to the lowest excited state (1s-1s), which eventually relaxes to the ground state with some fluorescence at 700 nm.
- OSTI ID:
- 370807
- Report Number(s):
- CONF-960376--
- Country of Publication:
- United States
- Language:
- English
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