Coherent ultrafast hot electron generation at plasmonic heterojunctions
2nd. May. 2018, Kolloquium, Saal MC122, Campus Duisburg, Universität Duisburg-Essen
Time:
Start: 2nd. May. 2018. 12:45
End: 2nd. May. 2018. 02:15 p.m.
Author(s):
Prof. Dr. Hrvoje Petek Department of Physics and Astronomy, University of Pittsburgh
Organizer(s):
Dr. Andreas Reichert Universität Duisburg-Essen
Abstract:
We study the plasmonic enhancement of hot electron generation, by measuring the
ultrafast electron spectroscopy and dynamics at Ag nanocluster-decorated graphite
and TiO2 surfaces by timeresolved multiphoton photoemission (mPP)
spectroscopy. Deposition of Ag onto the supporting substrates produces small
(5 nm dia., 1 nm high) Ag nanoparticles that support Mie plasmon resonances of
the metal nanoparticle-support system. Excitation of the plasmonic modes greatly
enhances the mPP yields over the bare substrates. Analysis of the mPP spectra
and hot electron relaxation rates show that hot electrons are generated directly in
the substrates by dephasing of the plasmon resonances. This is possible because
the plasmon resonances are electronically, optically, and chemically coupled with
the substrates. The coupling of molecules with the plasmonic modes causes
modification of the plasmon resonances and the mPP yields. We also find direct
coherent photoinduced electron transfer from Ag nanoclusters to graphite. The
probing of ultrafast polarization and hot electron dynamics reveals the energy and
charge coupling at plasmonic heterojunctions.1