title: Intrinsic vibrational coherence in face-centered cubic supra-crystals of silver nanocrystals: Raman scattering measurements.
abstract: The ordering of silver nanocrystals is tuned from amorphous aggregates to highly well-ordered, face-centered cubic supra-crystals, using various substrates and controlling their temperature to obtain this. Low-frequency Raman scattering, for the first time, demonstrates vibrational coherence in fcc supra-crystals of nanocrystals. This is shown by a narrowing of the peak corresponding to the quadrupolar modes of the nanocrystals. However, this is obtained when the supra-crystals are smaller than the excitation wavelength. When the supra-crystals are larger, the narrowing cannot be observed. Furthermore, for any size of the supra-crystals, a shift to low frequency of the Raman peak due to the Lorentz field effect is seen.
authors.affiliation: Laboratoire des Materiaux Mésoscopiques et Nanométriques, UMR-CNRS 7070, Université Pierre et Marie Curie, BP 52, 4 place Jussieu, 75252 Paris Cedex 05, France.
authors.forename: A
authors.initials: A
authors.lastname: Courty
authors.forename: P A
authors.initials: PA
authors.lastname: Albouy
authors.forename: A
authors.initials: A
authors.lastname: Mermet
authors.forename: E
authors.initials: E
authors.lastname: Duval
authors.forename: M P
authors.initials: MP
authors.lastname: Pileni