Ultrafast dynamics of electron localization at interfaces
- Univ. of California, Berkeley, CA (United States)
The dynamics of image potential electrons at alkane/Ag(111) interfaces were studied by angle-resolved two-photon photoemission spectroscopy (TPPE) with femtosecond time resolution. Optical excitation creates interfacial electrons in extended states which are characterized by a nearly free-electron mass for electron motion parallel to the interface. The initially delocalized state decays into a high-mass localized state within a few hundred femtoseconds via a self-trapping mechanism. The energy dependence of the self-trapping rate can be modeled as an activated barrier crossing between the delocalized and localized states. The lattice relaxation energy and the characteristic phonon energy that results in 2-D small polaron localization are determined. The subsequent decay of the localized electron back to the metal is on a longer time scale. This is due to the tunneling barrier created by the repulsive electron affinity of the adlayer. Our results show that angle and time resolved femtosecond TPPE serves as a powerful and general probe of electronic structure and carrier dynamics at interfaces.
- OSTI ID:
- 560378
- Report Number(s):
- CONF-970443--
- Country of Publication:
- United States
- Language:
- English
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