Ultrafast optical studies of electronic relaxation across the interface in CdS/CdSe/CdS quantum-dot quantum-well heterostructures

PHYS 56

Wei Qian1, Alexander W. Schill2, Christopher Gaddis, chris.gaddis@gmail.com1, and Mostafa A. El-Sayed, mostafa.el-sayed@chemistry.gatech.edu1. (1) Laser Dynamics Laboratory, School of Chemistry and Biochemistry, Georgia Institute of Technology, 770 State Street, Atlanta, GA 30332-0400, (2) Chemistry and Biochemistry, Georgia Institute of Technology, Boggs Chemistry, 770 State Street, Atlanta, GA 30339
The relaxation of excited electrons across interface in the CdS/CdSe/CdS quantum-dot quantum-well heterostructures has been explored by ultrafast optical spectroscopy. The rise process of transient stimulated emission signal monitoring the build-up of population of the lowest excited electronic state (1S state in CdSe well)shows two components. Via analysis of multi-wavelength pump-probe signals, these two components have been indentified as intra-band electronic relaxation within CdSe well (fast component) and interfacial electron transfer from CdS core to CdSe well (slow component). The transfer time of the electron from the CdS core into the CdSe well determined from the slow component is found to be 1.2 ps. We have also shown the simultaneous creation of excitions in both CdS core and CdSe well with intensity higher than the threshold of generation two excitons per nanocrystal. Our observation strongly indicates that the interacting chromophores is a good physical system for describing CdS/CdSe/CdS heterostructures.
 

Nanostructured Materials
1:20 PM-5:20 PM, Sunday, April 6, 2008 Morial Convention Center -- Rm. 338, Oral

Division of Physical Chemistry

The 235th ACS National Meeting, New Orleans, LA, April 6-10, 2008