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Environment friendly, thin and flexible devices require the synthesis of Indium-free new transparent conducting materials (TCM) with improved structural, thermal, electrical and optical properties. To overcome the critical issues raised by thinning the TCM, we propose a multilayer structure in which nanogranular Ag film obtained by supersonic cluster beam deposition is sandwiched in between Alluminum doped Zinc Oxide (AZO) thin layers. The introduction of the nanogranular Ag film, when compared to the standard sputtered one, yields higher optical transmittance in the technologically relevant VIS-NIR region and superior mechanical reliability while preserving low electrical resistance. The present results open new perspectives to exploit the nanogranular nature of conductive films, synthesized via Supersonic Cluster Beam Deposition, to engineer transparent conducting materials.

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.

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.

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.}

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 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.

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 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.

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.

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).

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.