Electronic states of semiconductor clusters: Homogeneous and inhomogeneous broadening of the optical spectrum

A. P. Alivisatos, A. L. Harris, N. J. Levinos, M. L. Steigerwald, L. E. Brus

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Abstract

The homogeneous (single-cluster) and inhomogeneous contributions to the low temperature electronic absorption spectrum of 35-50 Å diameter CdSe clusters are separated using transient photophysical hole burning. The clusters have the cubic bulk crystal structure, but their electronic states are strongly quantum confined. The inhomogeneous broadening of these features arises because the spectrum depends upon cluster size and shape, and the samples contain similar, but not identical, clusters. The homogeneous spectrum, which consists of a peak 140 cm-1 (17 meV) wide, with a phonon sideband and continuum absorption to higher energy, is compared to a simple molecular orbital model. Electron-vibration coupling, which is enhanced in small clusters, contributes to the substantial broadening of the homogeneous spectrum. The inhomogeneous width of the lowest allowed optical transition was found to be 940 cm-1, or seven times the homogeneous width, in the most monodisperse sample.

Original languageEnglish
Pages (from-to)4001-4011
Number of pages11
JournalThe Journal of Chemical Physics
Volume89
Issue number7
DOIs
Publication statusPublished - Jan 1 1988

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ASJC Scopus subject areas

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

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