Mechanisms for intraband energy relaxation in semiconductor quantum dots: The role of electron-hole interactions

Citation
Vi. Klimov et al., Mechanisms for intraband energy relaxation in semiconductor quantum dots: The role of electron-hole interactions, PHYS REV B, 61(20), 2000, pp. R13349-R13352
Citations number
22
Categorie Soggetti
Apllied Physucs/Condensed Matter/Materiales Science
Journal title
PHYSICAL REVIEW B
ISSN journal
01631829 → ACNP
Volume
61
Issue
20
Year of publication
2000
Pages
R13349 - R13352
Database
ISI
SICI code
0163-1829(20000515)61:20<R13349:MFIERI>2.0.ZU;2-C
Abstract
To evaluate the role of nonphonon energy relaxation mechanisms in quantum d ots and in particular the role of electron-hole (e-h) interactions, we have studied femtosecond carrier dynamics in CdSe colloidal nanoparticles in wh ich the e-h separation (coupling) is controlled using different types of su rface ligands. In dots capped with hole accepting molecules, the e-h coupli ng is strongly reduced after the hole is transferred to a capping group. By re-exciting an electron within the conduction band at different stages of hole transfer and monitoring its relaxation back into the ground state, we observe a more than tenfold increase in the electron relaxation time (from 250 fs to 3 ps) after the completion of the hole transfer to the capping mo lecule. This strongly indicates that electron relaxation in quantum dots is dominated not by phonon emission but by the e-h energy transfer.