Showing papers by "Moungi G. Bawendi published in 1992"

Luminescence properties of CdSe quantum crystallites: Resonance between interior and surface localized states

Abstract: We use time‐, wavelength‐, temperature‐, polarization‐resolved luminescence to elucidate the nature of the absorbing and ‘‘band edge’’ luminescing states in 32 A diameter wurtzite CdSe quantum crystallites. Time‐resolved emission following picosecond size‐selective resonant excitation of the lowest excited state shows two components—a temperature insensitive 100 ps component and a microsecond, temperature sensitive component. The emission spectrum, showing optic phonon vibrational structure, develops a ∼70 wave number red shift as the fast component decays. Photoselection shows the slow component to be reverse polarized at 10 K, indicating this component to be the result of a hole radiationless transition. The 100 ps emitting state is repopulated thermally as temperature increases from 10 to 50 K. All available data are interpreted by postulating strong resonant mixing between a standing wave molecular orbital delocalized inside the crystallite and intrinsic surface Se lone pair states. The apparent excit...