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We present the first results of microstructure replica with re-usable masters in poly vinyl alcohol (PVA). Microneedles of heights ranging from 500 to 1100 pm were fabricated through double-exposure deep Xray lithography (DXRL) process and successfully replicated. A single PVA master was used as a template to successfully replicate up to 10 PMMA microneedle arrays, suggesting that this method might be a possible alternative to PDMS processes. A preliminary characterization of the relationship between the surface roughness of the substrates and the force required for demoulding was also performed. (C) 2009 Elsevier B.V. All rights reserved.

This chapter overviews the major results obtained by scaning tunneling microscopy and spectroscopy on systems including the C60 molecule, starting from the free C60 molecule up to C60 in the solid state. The structural and electronic properties of fullerene films are described. Moreover, the behavior of fullerenes in low dimensional films obtained by molecular deposition on clean metal and semiconductor substrates are reviewied , as well as the influence on the film properties by external doping.

A single layer (SL) of pentacene molecules deposited on the Cu(119) surface and on an organic selfassembled monolayer (SAM) has been investigated by near-edge x-ray absorption fine structure (NEXAFS) at the C K edge, and by photoemission at the C 1s core level. The lowest unoccupied molecular orbitals (LUMOs) of the pentacene SL on the SAM are basically unaffected with respect to that of pentacene in the gas phase, indicating a weak interaction of pentacene with the SAM, while a strong redistribution of the LUMO-related final states is observed when the molecules are deposited on the Cu(119) substrate, sign of an electronic mixing between molecular and metal electronic states, in agreement with recent theoretical predictions. The strong dichroic response of the NEXAFS signal indicates upstanding pentacene molecules oriented 16° off normal for the organic-organic heterostructure. The rehybridization of pentacene orbitals with Cu states at the pentacene/Cu interface hinders an accurate determination of the molecule orientation, which is, however, compatible with molecules lying flat on the Cu(119) terraces.

The structure of the (33 x 33 )R30° and (13 x 13 )R14° phases of C60/Ge(111) single-layer has been studied by Scanning Tunneling Microscopy (STM). Sub-molecular resolution allows to distinguish among differently orientated molecules. In the (33 x 33 )R30° phase the molecules result to be arranged in rhomboidal groups of 4 molecules, named tetramers. The (2x2) periodicity in the domains of homogeneously oriented tetramers is due to the alternating orientation of the molecules within the tetramer, accounting for the observed (33 x 33 )R30° Low Energy Electron Diffraction (LEED) pattern. The symmetry of the molecular lattice suggests that the molecules interact only with the first layer of substrate atoms. The orientation of each molecule is mainly determined by the configuration of the substrate atoms in the adsorption site, even though a contribution from the intermolecular interaction is likely present. In the (13 x 13 )R14° phase the observed sub-molecular features indicate that all the molecules have the same adsorption configuration, with a hexagon facing the substrate. The threefold symmetry of the molecular lattice suggests that the C60 - Ge interaction involves also the atoms of the second layer of the substrate.

Ultrathin ordered films of TiOx (x~1) on Pt(111) has been investigated by scanning tunneling microscopy (STM) to test their capability as templates for growing ordered and monodispersed Au nanocluster arrays. The ordered array of parallel black troughs spaced by 1.44 nm, observed in the STM data of the zigzag-like TiOx ultrathin film, revealed to be a good template for growing a linear array of Au clusters, with a mean size of 1.3 nm and a narrow dispersion. The wagon-wheel-like TiOx film, having similar chemical composition but without a nanostructured array of defects, does not show templating effects, leading to nucleation of disordered and larger Au clusters (mean size of 3.4 nm with a large dispersion). Hence this work shows that the ordering of the deposited Au nanoclusters is strongly dependent on the actual defectivity of the film. Annealing the Au cluster arrays at high temperature produces drastic changes in the spatial arrangement of the clusters, which has been interpreted as the consequence of the changes in the ultrathin film template.

Cup-like structures of In, Sn and Nb on Si substrates with femtoliter capacity obtained by pulsed laser ablation, have been subjected to different oxidation treatments and examined employing spatially resolved scanning Auger spectroscopy and microscopy (SR-AES and SAM). The as-prepared cups, when exposed to ambient are found to have a native oxide layer on the surface that could be easily removed by Ar ion sputtering to result in clean metal cups, suitable for functionalization. In the case of In cups, the thin metal layer at the bottom of the cups could be removed easily by sputtering to form In rings. The cups subjected to external oxidation have a thicker oxide layer in comparison to in-situ dosing of oxygen. In the case of Nb cups, the high temperature treatment employed during oxidation resulted in segregation of Si to the surface of the cup. There is also evidence for the formation of metal-silicon alloy at the center of the cups, especially of Sn and Nb, during the oxidation treatment at elevated temperatures.

We have studied Fe films on Ar+ ion sputtered highly oriented pyrolitic graphite (HOPG) using scanning tunnelling microscopy (STM). The adsorbed Fe atoms form nanoparticles uniformly distributed over the substrate surface with narrow size distribution. Comparing these data with Fe deposited on non-sputtered HOPG indicates the role of substrate defects, acting as nucleation sites, on the overall film structure. However, the shape and size of individual defects do not seem to influence the shape of the nanoparticles. The correlation between the Fe film morphology and the sputtered substrate morphology is discussed taking into account the different capturing properties of sputtering-induced defects.

We have studied the scanning tunneling microscopy tip interaction with the naturally formed nanotube-like (NTL) structures on highly oriented pyrolytic graphite (HOPG) surface. Shape variations of the NT-like structures, caused by the modulation of scanning parameters, were observed and analyzed.

Electroencephalography (EEG) recordings can be used to help paralyzed patients by replacing functionality of damaged neural connections through the aid of a brain–computer interface. Conventional electrodes used for EEG require long skin preparation due to the impedance of the outermost layers of skin. On the contrary, dry spiked electrodes allow overcoming of impedance problems and can be suitable for long-term measurements. This paper describes microfabrication and packaging of micropatterned dry electrodes built with deep X-ray lithography, electroplating and soft lithography. Preliminary measurements performed with electrodes having different geometries are also described.

This work will provide an overview of recent experiments devoted to study the nature and properties of materials obtained in situ via cluster-assembling, by using supersonic cluster beam deposition. This technique has proved to be a powerful tool for assembling nanostructured materials with tailored physical properties, in particular for: 1) carbon-based clusters deposited in situ on appropriate substrates in Ultra High Vacuum compatible conditions; 2) a micro-structured pattern based on pristine carbon-based dots and then promoted to the formation of SiC via in situ thermal annealing; 3) thermo-chemically doped nanostructured TiO2, revealing the possibility to control the band gap of this material. The electronic structure of the systems has been studied combining a wide variety of experimental methods, including valence-band and core-level photoemission, Electron Energy Loss Spectroscopy, Scanning Auger Spectroscopy, Atomic Force Microscopy

We investigate the morphology of a pentacene (C22H14) film adsorbed on the Cu(119) vicinal surface by scanning tunnelling microscopy (STM). Thermal treatment of a thick film of molecules generates a long-range ordered structure. Series of molecular rows are alternated with areas where the molecules assume two equivalent orientations. STM data analysis suggests that the ordered structure can be described by a rippled morphology. The behaviour of the film at different annealing temperatures suggests a possible explanation of the film structure as due to an adsorbate-induced modification of the substrate

The authors present a combined photoemission and scanning-tunneling spectroscopy study of the filled electronic states, the molecular energy gap, and the energy level diagram of highly ordered arrays of pentacene deposited on the Cu(119) vicinal surface. The states localized at the interface are clearly singled out, comparing the results at different pentacene thicknesses and with gas-phase photoemission data. The molecular gap of 2.35 eV, the hole injection barrier of 1.05 eV, and the electron injection barrier of 1.30 eV determine the energy level diagram of the states localized at the pentacene molecules.

Pentacene (C22H14), deposited on the Cu(119) vicinal surface, forms ordered molecular chains, with the long molecular axis aligned along the step direction. Phase correlation between neighboring chains gives rise to large domains, observed in the low-energy electron-diffraction (LEED) pattern. Scanning tunneling microscopy (STM) images show that the molecules are laying flat on the copper terraces with the molecular axis aligned along the steps, hence, facing the short side of one another. High-resolution STM data suggest that the molecules adsorb, locating the central benzene ring on the hollow site of the Cu(001) surface.

We present a morphological study of pentacene (C22H14) long range ordered molecular wires assembled on the Cu(119) vicinal surface. At low pentacene coverage, scanning tunneling microscopy (STM) shows single molecules adsorbed flat on the surface, presenting the long side parallel to the terrace direction. At the completion of the first layer, the molecules line up in regular rows extending along the step edges. By increasing the coverage, the rows of pentacene molecules form a densely packed structure, presenting a pyramid-like shape perpendicular to the steps. (C) 2004 Elsevier B.V. All rights reserved.

We investigate one-dimensional (1-D) nanostructures formed by deposition of potassium on InAs(110) surface and of pentacene on the vicinal Cu(119) surface. Scanning tunneling microscopy (STM) reveals the morphology and the long-range ordering of the nanostructures. Voltage-dependent STM images are used to investigate the electronic structure in the real space. The potassium chains give rise to a delocalized continuum of charge density, suggesting their 1-D electronic nature. 1-D pentacene rows, growing beyond the completion of the first layer, do not show a similar behavior. The formation of the 1-D electronic structures is discussed in term of the substrate-adsorbate interaction. (C) 2004 Elsevier B.V. All rights reserved.

One-dimensional (1D) potassium chains, obtained on the InAs(110) surface, are studied by scanning tunneling microscopy (STM). The (2xn) symmetry in the low energy electron diffraction pattern, becoming a c(2x6) structure at the completion of the first layer, is explained by the various spacing D between alkali chains in the [001] direction. The distribution of D as a function of the chain density suggests the presence of a repulsive interaction among the chains, which drives the self-assembling of the 1D structures. The origin of the interaction is discussed in comparison with the model proposed for the Cs/InAs(110) interface, showing the general validity of the model for this class of chain structures. The atomic structure of an isolated chain is investigated by high-resolution STM images, revealing the asymmetry in the charge density induced by K adatoms and a modification of the As-related charge density of the topmost substrate layer.

We investigate the electronic band dispersion associated to alkali metal chains assembled on the InAs(110) surface by angular-resolved photoelectron spectroscopy. The Cs and K atomic chains induce occupied electronic states with twofold symmetry and narrow bandwidth along the chain direction, showing a quasi-one-dimensional electronic character. The insulating character and the narrow bandwidth of the alkali-induced state suggest the relevance of electron correlation effects in the description of alkali-induced electronic-state dispersion.

In this paper, we present photoemission experiments on the hole-doped Haldane chain compound Y2-xSrxBaNiO5. By using the photon energy dependence of the photoemission cross section, we identified the symmetry of the first ionisation states (d type). Hole doping in this system leads to a significant increase in the spectral weight at the top of the valence band without any change in the vicinity of the Fermi energy. This behavior, never observed in other charge transfer oxides, could result from the Ni-3d-O-2P hybridization enhancement due to the shortening of the relevant Ni-O distance with doping. (C) 2002 Elsevier Science B.V. All rights reserved.

Potassium induced one-dimensional nanostructures are formed by deposition on the InAs(I 10) surface held at about 420 K, as observed by scanning tunneling microscopy. The K adatoms self-aggregate in zigzag chains oriented along the {[110] direction even at very low coverage. By increasing the K density, the atomic chains pack together, though keeping a minimum distance of 18.2 Angstrom. At the completion of the first layer, the nanostructures extend over the entire surface giving rise to a clear c(2 x 6) low energy electron diffraction pattern. At higher coverage, a second ordered overlayer is formed. The results are discussed in terms of recent theoretical calculations and experimental work on the model system of Cs chains self-assembled on the InAs(l 10) surface. The structural model proposed for a single chain is used to discuss the evolution of the overlayer structure as a function of coverage. (C) 2003 Elsevier Science B.V. All rights reserved.}

Long-range ordered chain structures can be assembled by depositing potassium on the clean InAs(110) surface held at 420 K. Potassium wires are formed along the {[1 (1) over bar0] direction at coverage as low as Theta = 0.02, as observed by scanning tunneling microscopy. The chain density increases by further K adsorption and a c(2 x 6) symmetry can be detected by LEED at the completion of the first ordered layer. Further deposition induces a second ordered potassium overlayer on top of the alkali wires with a c(4 x 4) symmetry. The regularly-shaped unit blocks are constituted by four potassium adatoms aligned along the underlying row structure. Scanning tunneling spectroscopy (STS) does not detect an electronic density of states at the fermi level indicating the insulating character of the one-dimensional (1D) and two-dimensional (2D) systems. (C) 2003 Elsevier Science B.V. All rights reserved.}

In this paper, we present photoemission experiments on the hole-doped Haldane chain compound Y2-xSrxBaNiO5. By using the photon-energy dependence of the photoemission cross section, we identified the symmetry of the first ionization states (d type). Hole doping in this system leads to a significant increase in the spectral weight at the top of the valence band without any change in the vicinity of the Fermi energy. This behavior, not observed in other charge-transfer oxides at low doping level, could result from the inhomogeneous character of the doped system and from a Ni 3d-O 2p hybridization enhancement due to the shortening of the relevant Ni-O distance in the localized hole-doped regions.

We present a study of the thermal evolution of the Ag/Ge(1 1 1) interface by combining Scanning Electron Microscopy (SEM), Low Energy Electron Diffraction (LEED), Spatially Resolved Auger Electron Spectroscopy (SR-AES), and Atomic Force Microscopy (AFM). We followed the morphological and structural changes of a thick Ag film grown onto Ge(1 1 1)-c(2 x 8) at 300 K after annealing at selected temperatures between 370 and 800 K. The morphology of the system evolves from a flat film up to the nucleation of islands through the formation of dendritic structures. The diffraction pattern shows different intermediate surface reconstructions. We report evidences of Ge intermixing into the Ag growing layer and segregation on top of it. (C) 2003 Elsevier Science B.V. All rights reserved.

We performed angle-resolved photoelectron spectroscopy (ARPES) and resistivity measurements on the layered metal 1T-TiTe2. We determined the quasiparticle dispersion and lifetime. In particular, we could characterize and separately evaluate the effects of the electron-electron and electron-phonon interactions on the experimental spectra. The good correlation between transport and spectroscopic scattering rates indicates that this material behaves as a model Fermi liquid system.

The emerging fields of graphene-based magnetic and spintronic devices require a deep understanding of the interface between graphene and ferromagnetic metals. This work reports a detailed investigation at the nanometer level of the Fe-graphene interface carried out by angle-resolved photoemission, high-resolution photoemission from core levels, and scanning tunnelling microscopy. Quasi-freestanding graphene was grown on Pt(111), and the iron film was either deposited atop or intercalated beneath graphene. Calculations and experimental results show that iron strongly modifies the graphene band structure and lifts its pi band spin degeneracy.

We present a high-resolution ultraviolet photoelectron spectroscopy study of the room temperature Cs chain formation on InAs(110), analysing the valence band spectra and core levels in the whole coverage range from the self-assembling of the Cs chains to the cluster uptake at saturation coverage. The valence band data shows an insulating behaviour up to saturation coverage. The adsorption sites have been monitored by means of Cs-4d, In-4d and As-3d core levels. The Cs-4d core-level data shows two distinct components, consistent with the presence of two unequivalent Cs adsorption sites in the Cs nanowire. The In-4d and As-3d levels show Cs-induced extra components due to electronic level re-hybridization to the substrate atoms, and predominant charge transfer from Cs adatoms to In, in agreement with recent theoretical calculations. (C) 2001 Elsevier Science B.V. All rights reserved.

Using high-resolution angle-resolved photoemission spectroscopy (ARPES). we examined the charge density wave (CDW) compound 1T-TaS2 as a function of the photon energy (energy range from 11 up to 33 eV) for both quasicommensurate (QC) and commensurate (C) CDW phases, While the QC-phase normal emission ARPES spectra coincide with previous results, normal emission spectra of the C phase reveal evidence for a fine structure in the CDW-induced features between 1 eV binding energy and the Fermi level. This fine structure may be explained by the subband manifold of the Ta 5d band, split off due to the CDW-induced root13 x root13 superstructure.

We present a combined angle-resolved photoemission spectroscopy and resistivity study of the model Fermi liquid system 1T-TiTe2. From the analysis of the quasiparticle spectral line shape we identify and separately evaluate the electron-electron, electron-phonon, and impurity scattering contributions to the quasiparticle lifetime. There is a clear correspondence between spectroscopic and transport data. A residual low-temperature spectral linewidth (G0=17 meV) indicates that the three-dimensional nature of the electronic states cannot be neglected even in this quasi-two-dimensional material.

A high resolution fore-level photoemission investigation of 2D ordered Bi layers grown on Si(100)-(2 x 1) is presented. We study the Si 2p and Bi 5d core-levels at room temperature as a function of coverage and in the reconstructed phases. The different Bi structural configurations around the monolayer coverage and in the (2 x n)-reconstructed phase are derived from the core-level lineshape evolution. By following the Fermi level pinning, the presence of Bi-induced occupied electronic states close to the Si mid-gap is suggested. (C) 1999 Elsevier Science B.V. All rights reserved.

Bismuth adsorbs on the Si(001)-(1 x 2) surface in the form of rows of dimers. Missing-dimer lines (MDLs) are created perpendicularly every n units, leading to (2 x n) periodicity. Depending on the coverage, n can vary from 12 to 5. We investigated by grazing incidence x-ray diffraction the (2 x n) structure, with n = 6.45. The disorder in the MDL periodicity, as well as the defects along the MDL, reduce considerably the correlation length of the reconstructed domains. As a consequence, the integrated intensity of each reflection must be corrected, evaluating the trace of the resolution function across the diffraction node. The structural refinement, based on the as-derived intensities, provides the Bi dimer bond length (3.11 Angstrom) the Si atom positions (bulklike), and the height of the Pi plane with respect to Si (1.88 Angstrom). In addition, we give evidence that the dimers are displaced along the row from ideal positions towards the MDL (from 0.15 to 0.50 Angstrom). Last, the diffraction profiles are calculated, on the basis of a probability distribution of (2 x n) cells (n = 6, 7, 1), using the phase-matrix method. The average positions of the fractional peaks are related to the concentration of each type of cell. The width and the intensity of the second order peaks, compared to those of the first order peaks, allow us to account for the aggregation tendency.

Bismuth adsorbed on Si(001) induces successive (2 x n) phases after annealing, with n ranging from 12 to 5. The structure consists of dimer rows, with missing-dimer defects forming and ordering in the perpendicular direction. We investigated by grazing-incidence X-ray diffraction the n = 6.45 surface, which results from missing-dimer line ordering each 6 or 7 units. The structural refinement is based either on a (2 x 6) or a (2 x 7) cell. The Bi dimers are lying at 1.86 Angstrom on top of Si, with a dimer bond length of 3.11 Angstrom. They are displaced along the row towards the missing dimer, while the Si atoms are at bulk positions. A photoemission study of the Bi 5d and Si 2p core levels confirms the model of symmetric Bi dimers, after breaking Si dimers, The diffracted intensity is calculated using the phase-matrix method. The positions and widths of the peaks are analysed in terms of the dimer blocks probability distribution. (C) 1999 Elsevier Science B.V. All rights reserved.

Growth and transport properties of thin Ag films on Si(lll) are investigated by scanning tunneling microscopy and in situ resistivity measurements. At low coverage, the Ag adatoms form isolated islands with a strongly preferred height and flat tops, rather than commonly observed pyramids. Such plateaus increase their lateral extent with coverage without changing height, forming a percolated network with sharply reduced resistivity above a critical coverage. This behavior suggests how the quantized electrons confined in the Ag islands could influence the growth, and may provide a unique pathway to prepare nanometer-scale structures with intriguing mesoscopic properties.

An investigation of the electronic properties of the Bi/Si(100) interface in the early growth stage is presented. Bi-induced occupied electronic states and absorption features are determined through the complementary UV photoemission spectroscopy and high resolution electron energy loss spectroscopy in the energy gap region. The interface is clearly semiconducting at half-monolayer coverage, with a surface energy gap of 1.1 eV, greater than that of the clean Si(100) surface. This behavior can be understood by considering the saturation of the topmost layer silicon dimer dangling bonds by the Bi adatoms. The interface assumes a weak semimetallic character at the completion of one monolayer, probably because of the formation of Bi-Bi adatom bonds. Space charge layer formation and a slight downward band bending. (C) 1998 Elsevier Science B.V. All rights reserved.

The structure of the GaSb(110)(1 x 2)-Bi reconstruction has been solved using surface x-ray diffraction, scanning tunneling microscopy, and photoelectron spectroscopy. The ideal GaSb(110) surface is terminated with zigzag chains of anions and cations running in the [1 (1) over bar 0] direction. In the Bi-induced (1 X 2) reconstruction we find that every second zigzag chain in the uppermost substrate layer is missing. The reconstructed surface is terminated with a full monolayer of Bi atoms which also form zigzag chains. The Bi atoms in the chains bond alternately to the first and second layer substrate atoms and the Bi chains are inclined at 34 degrees to the (110) plane

Annealing of a thin Bi layer grown on the Si(100)-(2 x 1) surface is known to produce well-ordered (2 x n) reconstructions. To investigate the Bi-induced electronic properties in these different structural configurations, we present ultraviolet photoemission and high-resolution electron energy loss spectroscopies on this interface. The adsorption of Bi produces clear modification of the substrate dimer-related surface states. On the (2 x n)-Bi reconstructed phases the data show a clear semiconducting behaviour, with the opening of a surface gap larger (1.3 eV) than that observed on the clean Si(100)-(2 x 1) surface (0.4 eV). Moreover, electronic states are detected within the gap up to 280 degrees C annealing temperature, whose possible origin is discussed. The absence of electronic excitations in the enlarged gap region and the modified density of occupied states observed for higher annealing temperatures (< 500 degrees C) suggest that the Bi adatoms induce breaking of the underlying Si-Si dimers.

The Si(100) surface is constituted by asymmetric dimers and presents complex dynamical behaviour. To understand the influence of dimer motion on the surface electronic properties, we investigate the dynamics of the Si(100) surface experimentally and theoretically in a wide temperature range (150-00K). High-resolution electron energy-loss spectroscopy measurements are compared to a microscopic tight-binding calculation of the dielectric function. An instantaneous symmetric-like nat dimer configuration due to fast dimer-flipping is responsible for the electronic transition at 0.8 eV and for the surface metallization observed at 900 K,well below the suggested incomplete melting temperature (1400 K).

High-temperature surface metallization of Si(100) is observed at T > 900 K by high-resolution electron-energy-loss and ultraviolet photoemission spectroscopy. Metallization takes place well below the incomplete surface melting temperature and is consistent with the Si dimer dynamics, characterized by an instantaneous symmetriclike dimer configuration. The surface free carrier concentration in the metallic phase has been evaluated, reaching (at 1170 K) the same order of magnitude of the surface dimer density.

An investigation and a comparison of the Bi-induced electronic states at the (2 X 1)-Bi/InSb(110) and (2 X 1)Bi/GaSb(110) interfaces is presented. The electronic transitions between Bi-induced states have been studied by high-resolution electron energy loss spectroscopy: a huge absorption structure is found at 0.48 eV in the stable (2 X 1) reconstructed phase for the Bi/InSb(110) interface, and at 0.55 eV for the (2 X 1)-Bi/GaSb(110) interface. This feature distinguishes an interband electronic transition between Bi-induced filled and empty electronic states, for both (2 X 1)-symmetry interfaces. Moreover, the Bi-induced occupied states are detected in the valence band for both systems, by ultra-violet photoemission spectroscopy.

The surface electronic structure of the clean Si(100)-(2x1) surface at room temperature is studied by high-resolution electron-energy-loss spectroscopy. Main absorption edge is detected at similar to 0.4 eV, which corresponds to the energy gap of the system, further structures are singled out at 0.8 and 1.25 eV and ascribed to interband electronic transitions between dimer-related levels. The paramount importance of cleanness is addressed showing and quantifying the effect of the residual gas atmosphere (that can be present in ultrahigh vacuum) on the electronic structure.

The overlayer growth and electronic properties of the Bi/GaSb(110) interface and of the two-dimensional ordered (1×1)- and (1×2)-Bi layers have been investigated by complementary spectroscopic techniques (high-resolution electron-energy-loss, photoemission, and Auger spectroscopy). Bismuth forms an epitaxial monolayer, followed by island formation (Stranski-Krastanov growth mode) covering an average surface area of 40% at a nominal coverage of 4 ML. The (1×2)-symmetry stable structural phase, obtained after annealing at ~220 °C, corresponds to an average nominal Bi coverage of about 0.7 ML, suggesting an atomic geometry different from the epitaxial-continued layer structure. The disposal of Bi atoms in the (1×2) structure should build up an ``open'' layer, as the Ga-related surface exciton quenched in the (1×1) epitaxial monolayer is present in the (1×2) stable phase. The two symmetry phases are characterized by strong absorption features at 1 eV [(1×1)-Bi] and 0.54 eV [(1×2)-Bi], related to interband electronic transitions between Bi-induced electronic states. The major Bi-related occupied electronic levels, present in the valence band of the (1×1)- and (1×2)-Bi layer, have been detected by angle-integrated ultraviolet photoemission spectroscopy. Both the (1×1) and (1×2) phases show a metallic nature, with a low density of electronic states at the Fermi level. Schottky barrier heights of 0.20 and 0.14 eV are estimated for the epitaxial (1×1)- and (1×2)-symmetry stage, respectively, by analyzing the space-charge layer conditions through the study of the dopant-induced free-carrier plasmon in the GaSb substrate.

A spectroscopic study of 10,10-dibromo-9,9 bianthracene (DBBA) molecules deposited on the Au(110) surface is presented, by means of ultraviolet and X-ray photoemission, and X-ray absorption spectroscopy. Through a thermally acti- vated procedure, these molecular precursors polymerize and eventually form graphene nanoribbons (GNRs) with atomically controlled shape and width, very important building blocks for several technological applications. The GNRs observed by scanning tunneling microscopy (STM) appear as short segments on top of the gold surface reconstruction, pointing out the delicate balance among surface diffusion and surface corrugation in their synthesis on the Au(110) surface.

We present a high-resolution electron-energy-loss-spectroscopy study of the electronic and dielectric properties of the (1 X 1) and (1 X 2) Bi/GaSb(110) interfaces, in the energy region of the semiconductor bulk gap. Among the semimetal/III-V(110) interfaces, we found this as the unique ordered-system showing a semimetallic character when one monolayer of semimetal is deposited on the (110) surface, at room temperature. Electronic loss structures induced by transitions among localized states have been identified for the (1 X 1) interface, the most prominent lying at about I eV. The (1 X 2) superstructure, produced through an appropriate thermal treatment, is still semimetallic, while the electronic loss structures shift to lower energies and present a clear dependence on the symmetry direction of the surface Brillouin zone.