Dynamics of exciton localization in CdS/HgS quantum-dot quantum wells

2019-10-25 14:16:11

quantum CdS phonon exciton HgS

责任者: Yeh, A.T.;Cerullo, G.;Banin, U.;Mews, A.;Alivisatos, A.P.;Shank, C.V. 单位: Dept. of Chem., California Univ., Berkeley, CA, USA 来源出处: Physical Review B (Condensed Matter)(Phys. Rev. B, Condens. Matter (USA)),1999/02/15,59(7):4973-9 摘要: Localization of carrier wave functions to the quantum-well portion of the CdS/HgS quantum-dot quantum well (QDQW) is investigated. Nanosecond hole-burning (HB) spectra measure the photoinduced exciton coupling to a 250-cm-1 HgS phonon mode indicative of localization. Femtosecond pump-probe spectroscopy of these QDQW, however, show the photoinduced exciton couples to coherent 300-cm-1 CdS longitudinal optical-phonon modes, which is indicative of delocalization throughout the QDQW. Femtosecond HB and three pulse pump-dump experiments reveal these results are dependent on the time scale of the experiment. These experiments indicate that the initially photoexcited electron and hole wave functions are weakly confined to the HgS monolayer. Only after long times (~400 fs) will the exciton localize to the HgS well. These results indicate that the primary optical interaction excites electrons from a delocalized QDQW ground state and not from a localized HgS well state 关键词: cadmium compounds;ground states;II-VI semiconductors;mercury compounds;optical hole burning;phonon-exciton interactions;semiconductor quantum dots;semiconductor quantum wells;time resolved spectra;wave functions;exciton localization dynamics;CdS/HgS quantum-dot quantum wells;carrier wave functions;nanosecond hole-burning spectra;photoinduced exciton coupling;HgS phonon mode;femtosecond pump-probe spectroscopy;CdS longitudinal optical-phonon modes;delocalization;three pulse pump-dump experiments;HgS monolayer;primary optical interaction;ground state;400 fs;CdS-HgS