Femtosecond Dynamics of Electron Localization at Interfaces

The dynamics of two-dimensional small-polaron formation at ultrathin alkane layers on a silver(111) surface have been studied with femtosecond time- and angle-resolved two-photon photoemission spectroscopy. Optical excitation creates interfacial electrons in quasi-free states for motion parallel to...

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Bibliographic Details
Published in:Science (American Association for the Advancement of Science) 1998-01, Vol.279 (5348), p.202-205
Main Authors: N.-H. Ge, Wong, C. M., Lingle, R. L., McNeill, J. D., Gaffney, K. J., Harris, C. B.
Format: Article
Language:English
Subjects:
Alkanes
Charge carriers
Condensed matter: electronic structure, electrical, magnetic, and optical properties
Crystal lattices
Electron and ion emission by liquids and solids
impact phenomena
Electron tunneling
Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures
Electrons
Energy
Exact sciences and technology
Interfaces, heterostructures, nanostructures
Kinetic energy
Kinetics
Lattice energy
Perceptual localization
Photoemission and photoelectron spectra
Physics
Polarons
Scientific Concepts
Surface and interface electron states
Surface science
Surface states, band structure, electron density of states
Surfaces (Physics)
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Summary:The dynamics of two-dimensional small-polaron formation at ultrathin alkane layers on a silver(111) surface have been studied with femtosecond time- and angle-resolved two-photon photoemission spectroscopy. Optical excitation creates interfacial electrons in quasi-free states for motion parallel to the interface. These initially delocalized electrons self-trap as small polarons in a localized state within a few hundred femtoseconds. The localized electrons then decay back to the metal within picoseconds by tunneling through the adlayer potential barrier. The energy dependence of the self-trapping rate has been measured and modeled with a theory analogous to electron transfer theory. This analysis determines the inter- and intramolecular vibrational modes of the overlayer responsible for self-trapping as well as the relaxation energy of the overlayer molecular lattice. These results for a model interface contribute to the fundamental picture of electron behavior in weakly bonded solids and can lead to better understanding of carrier dynamics in many different systems, including organic light-emitting diodes.
ISSN:0036-8075
1095-9203
DOI:10.1126/science.279.5348.202