9731642 Guyot-Sionnest This research by Professor P. Guyot-Sionnest of the James Franck Institute of the University of Chicago addresses crucial questions of the behavior of quantum dots/quantum wells, also known as artificial atoms or single electron transistors (SET). Among these is the predicted "phonon bottle neck" which would severely limit the applicability of SETs in nanotechnological applications. The typical size of a quantum dot (QD) is of the order of 1000 times that of a free atom yet very much smaller than that of conventional semiconductor elements. Their quantum mechanical behavior can thus not be predicted by simple scaling or extrapolation and must be determined by experimental work. In this research the PI will fabricate QDs using colloidal nanocrystals rather than those made by conventional semiconductor fabrication techniques. Infrared intraband pump-probe spectroscopy will be used to determine the relaxation kinetics of electronically excited QDs. This will be done in stages over the duration of the grant: excited state spectroscopy by single color spectroscopy of optically excited QDs, and investigation of the dynamics and fine structure of intraband transitions by dual-color infrared pump-probe spectroscopy of optically excited QDs. These experiments will advance our knowledge of the relaxation dynamics of the electronic states of a QD, which is a basic issue that is key to the future generation of optical devices based on QDs. %%% This research by Professor P. Guyot-Sionnest of the James Franck Institute of the University of Chicago addresses crucial questions of the behavior of quantum dots/quantum wells, also known as artificial atoms or single electron transistors (SET). Among these is the predicted "phonon bottle neck" which would severely limit the applicability of SETs in nanotechnological applications. The typical size of a quantum dot (QD) is of the order of 1000 times that of a free atom yet very much smaller than that of conventional semiconductor elements. Their quantum mechanical behavior can thus not be predicted by simple scaling or extrapolation and must be determined by experimental work. In this research the PI will fabricate QDs using colloidal nanocrystals rather than those made by conventional semiconductor fabrication techniques. Infrared intraband pump-probe spectroscopy will be used to determine the relaxation kinetics of electronically excited QDs. This will be done in stages over the duration of the grant: excited state spectroscopy by single color spectroscopy of optically excited QDs, and investigation of the dynamics and fine structure of intraband transitions by dual-color infrared pump-probe spectroscopy of optically excited QDs. These experiments will advance our knowledge of the relaxation dynamics of the electronic states of a QD, which is a basic issue that is key to the future generation of optical devices based on QDs. *** ***
