Vibrational properties of carbon nanostructures Since 1996 the lab has been studying carbon-based materials by Raman and Brillouin scattering. We investigated acoustic modes in carbon nanotubes, in PTFE films and the elastic properties of ultrathin (2-4 nm) DLC films. Cluster assembled carbon films have been investigated in collaboration with Molecular Jets and Nanocrystalline Materials Lab (prof. P. Milani). Raman spectrosocpy revealed a correlation between the inertial focusing effects of supersonic cluster beams on material structural properties (degree of structural order/disorder). Brillouin spectrosocpy permitted the determination of film mesoscopic elastic constants and to observe a cross-over between a propagating and a localized regime of acoustic vibrations as a function of the nano- and mesostructure. In years 2001-2004, in collaboration with Molecular Jets and Nanocrystalline Materials Lab (prof. P. Milani) and thanks to an official agreement on nanotechnologies between Politecnico di Milano and Universita' di Milano, a Pulsed Microplasma Cluster Source (PMCS) hosted in the CLARA (Cluster Assembling Roaming Apparatus) apparatus for supersonic cluster beam deposition (SCBD) was connected to a UHV deposition chamber for in situ Raman charaterization. Since then research activity is being devoted to in situ Raman studies of cluster assembled carbon films. We showed the presence of metastable carbon structures with sp hybridization (polyynes and cumulenes). These structures reacts both with inert (He, Ar, N2) and reactive gases (H2, O2) and show a peculiar thermal stability.
From 2004 we are also investigating isolated linear carbon chains (polyynes). Polyynes are produced by prof. F. Cataldo (Rome) and are studied by Raman and SERS (Surface Enhanced Raman Scattering) in collaboration with the Molecular Dynamics and Vibrational Spectroscopy Lab (prof. G. Zerbi), Chemistry Department of the Politecnico di Milano. Such activity is in the framework of the NEMAS Center. Selected publications :
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Micro and Nanostructured Materials Lab, Department of Energy Politecnico di Milano Via Ponzio 34/3 I-20133 Milan, Italy |