Abstract
Confined acoustic phonons in InAs nanocrystals are observed in the time domain by femtosecond pump-probe spectroscopy. The size dependence of both frequency and damping time is investigated for InAs. The frequency of the discrete modes varies between 18 and 30 for a nanocrystal radius ranging from 28 to 12 Å, and the dependence deviates from the expected behavior at small sizes. The damping rate is found to vary linearly with suggesting coupling to the matrix through the particle surface as a main damping route. This is corroborated by observing faster damping for the acoustic mode in solution compared to a polymer environment. The coupling strength is found to depend on material parameters: in CdSe nanocrystals, weaker coupling is observed. The role of acoustic phonon coupling in the dephasing dynamics of semiconductor nanocrystals is discussed.
- Received 1 October 1998
DOI:https://doi.org/10.1103/PhysRevB.60.1928
©1999 American Physical Society