Enhancement of electron-hole exchange interaction in CdSe nanocrystals: A quantu

2019-10-10 10:16:41

The excitation line energy phonon

责任者: Chamarro, M.;Gourdon, C.;Lavallard, P.;Lublinskaya, O.;Ekimov, A.I. 单位: Groupe de Phys. des Solides, Paris VII Univ., France 来源出处: Physical Review B (Condensed Matter)(Phys. Rev. B, Condens. Matter (USA)),1996/01/15,53(3):1336-42 摘要: Photoluminescence of CdSe nanocrystals in a glass matrix was investigated at low temperature with size-selective excitation. The emission spectrum consists of a line a few meV below the excitation laser energy (denoted the F line) and a two-phonon replica superimposed on a broadband. The energy difference between the excitation energy and the F-line position increases with decreasing nanocrystal size. From the analysis of the time behavior of the luminescence and the degree of linear polarization, we attribute the F line to the recombination of the optically forbidden A exciton. Radiation recombination is made possible through a phonon-assisted virtual transition to the confined B-exciton state. The experimental degree of linear polarization is in good agreement with the theoretical calculations. The value of the electron-hole exchange energy obtained from the energy separation between the excitation energy and the F line is much larger than the bulk value and reaches 24 meV in 30-Å-diam. nanocrystals. The size dependence of the exchange energy is in good agreement with the theoretical prediction in the limit of small nanocrystals 关键词: cadmium compounds;electron-hole recombination;exchange interactions (electron);excitons;II-VI semiconductors;nanostructured materials;phonon-phonon interactions;photoluminescence;quantum interference phenomena;semiconductor doped glasses;electron-hole exchange interaction;CdSe nanocrystals;quantum confinement effect;photoluminescence;semiconductor;size-selective excitation;emission spectrum;F line;two-phonon replica;excitation energy;linear polarization;optically forbidden A exciton;phonon-assisted virtual transition;CdSe