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2001
Journal Article
Titel
Diffusion and aggregation of Agn-clusters (n=2-9) on HOPG probed by fs-two-photon-photoemission
Abstract
The diffusion and aggregation of preformed Agn-clusters (n = 2-9) deposited onto a highly oriented pyrolytic graphite (HOPG) substrate is studied by two-photon-photoemission (2PPE). The sample is irradiated with ultrashort laser pulse pairs and the kinetic energy of the emitted photoelectrons is analyzed in a magnetic bottle type time-of-flight spectrometer. During annealing of the sample from 100 K up to room temperature, nanoparticles are formed on the surface by diffusion and aggregation of the silver clusters. A steep increase of the total photoelectron yield at a sample temperature of about 150 K is explained by the excitation of plasmons in the silver nanoparticles. From the kinetic energy distribution of the photoelectrons we deduce a strong. variation of the work function of the sample during the formation of the nanoparticles, which is attributed to a quantum size effect.
Tags
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aggregation
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atomic clusters
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graphite
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metal clusters
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photoelectron spectra
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photoemission
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silver
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surface diffusion
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time of flight spectra
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two-photon spectra
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diffusion
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agn-clusters
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hopg
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fs-two-photon-photoemission
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highly oriented pyrolytic graphite
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ultrashort laser pulse pairs
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kinetic energy
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magnetic bottle type time-of-flight spectrometer
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room temperature
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nanoparticles
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photoelectron yield
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plasmons
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photoelectrons kinetic energy distribution
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quantum size effect
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100 k
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150 k
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298 k
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ag
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c