The photon-excited multipole plasmon and the bulklike plasmon modes have been studied in Na/Al͑111͒ and K/Al͑111͒. These collective modes appear for a coverage of у2 monolayers. Both the multipole and the bulklike plasmon modes exhibit interesting variations in frequency, line shape, and relative intensity with adlayer coverage. The reasons for such behavior are discussed on the basis of existing theoretical results. The substrate Al multipole plasmon is found to be attenuated by smooth adlayer growth. Deposition of K on two monolayer Na/Al͑111͒ results in the growth of K related collective excitation at the expense of the Na modes. For complicated surface structures like Al(111)-(ͱ3ϫͱ3)R30°:K or the Al͑111͒-͑2ϫ2͒:Na surface alloy, electron charge-density profiles at the surface are calculated based on ab initio density-functional theory-localdensity approximation method to explain the photoyield data. The importance of the shape of the chargedensity profile in determining the collective excitations is demonstrated. For Al(111)-(ͱ3ϫͱ3)R30°:K, a strong increase in intensity in the energy region of the K plasmons is observed in the on-top structure which is attributed to a ''mixed plasmon'' mode. These results show that while the experimental observations for smooth alkali-metal adlayers are in good agreement with existing theory, more theoretical work, especially for the complicated surface structures, is desirable.

Carbon nanotubes (CNTs) were synthesized by Chemical Vapor Deposition (CVD) from the pyrolytic decomposition of Iron Phthalocyanine (FePc) molecules, on SiO2/Si(111) substrates in the presence of a hydrogen flow. FePc molecules contribute simultaneously both to the formation of the precursor Fe nanoparticles and also as a Carbon source. Different experimental conditions were examined. Samples were characterized by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, and inverse photoemission. The resulting samples are highly oriented multiwall carbon nanotubes films, with heights in the range between: 4 and 20 microm. The tubes diameter is strongly dependent on growth temperature. Our experimental results show evidence of a transition in the growth mechanism, from a tip growth to a base growth mode, as the decomposition temperature is increased. Preliminary spectroscopic measurements performed on these MWCNTs, show the unoccupied density of states has several resonances close to Fermi level, related both to the graphene electronic structure and the formation of the tube.

We present results from Inverse photoemission spectroscopy in the isochromat mode, with angular resolution, from the clean Au (113)

Multiwall Carbon Nanotubes (MWCNTs) were synthesized by Chemical Vapor Deposition (CVD). Two different procedures were used to grow MWCNT films roughly, aligned in the direction normal to the SiO 2 /Si(111) substrate. Inverse Photoemission Spectroscopy measurements, on these samples, show the existence of resonances which could be traced back to a flat graphene sheet. The unoccupied valence band is fairly similar to that shown by graphite except by an additional intensity in the vicinity of the Fermi level. This resonance could be interpreted both as tubes tips end effects or van Hove singularities in the density of states.

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