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Heavy fuel oil (HFO) particulate matter (PM) emitted by marine engines is known to contain toxic heavy metals, including vanadium (V) and nickel (Ni). The toxicity of such metals will depend on the their chemical state, size distribution, and mixing state. Using online soot-particle aerosol mass spectrometry (SP-AMS), we quantified the mass of five metals (V, Ni, Fe, Na, and Ba) in HFO-PM soot particles produced by a marine diesel research engine. The in-soot metal concentrations were compared to in-PM2.5 measurements by inductively coupled plasma-optical emission spectroscopy (ICP-OES). We found that, Environmental Science & Technology, 52 (11), ISSN:0013-936X, ISSN:1520-5851

Capabilities of highly sensitive surface-enhanced infrared absorption (SEIRA) spectroscopy are demonstrated by exploiting large-area templates ($cm^2$) based on self-organized (SO) nanorod antennas. We engineered highly dense arrays of gold nanorod antennas featuring polarization-sensitive localized plasmon resonances, tunable over a broadband near- and mid-infrared (IR) spectrum, in overlap with the so-called 'functional group' window. We demonstrate polarization-sensitive SEIRA activity, homogeneous over macroscopic areas and stable in time, by exploiting prototype self-assembled monolayers of IR-active octadecanthiol (ODT) molecules. The strong coupling between the plasmonic excitation and molecular stretching modes gives rise to characteristic Fano resonances in SEIRA. The SO engineering of the active hotspots in the arrays allows us to achieve signal amplitude improved up to 5.7%. This figure is competitive to the response of lithographic nanoantennas and is stable when the optical excitation spot varies from the micro- to macroscale, thus enabling highly sensitive SEIRA spectroscopy with cost-effective nanosensor devices., 28+8 pages, 3+5 figures

Since its discovery, surface-enhanced Raman spectroscopy (SERS) has pushed researchers' interest to develop different kinds of active substrates for high sensitivity molecular detection. Defocused ion beam sputtering (IBS) represents a viable route for the production of large scale, highly reproducible SERS-active substrates consisting of near-field coupled nanowires featuring localized surface plasmon resonances in the visible and the near-infrared. Here we investigate the field enhancement and spatial confinement in the visible and the near-infrared of arrays of optically resonant gold nanowires, using two complementary techniques: SERS and scanning near-field optical microscopy (SNOM). While SERS allows us to quantify the field enhancement factor, SNOM is used to image the localization of the enhanced electromagnetic fields. We show that in the visible (633 nm) the nanowires are SERS active only for excitation polarized parallel to the wire-to-wire nanocavities, yielding enhancement factors of 7 X 10(3). In the near-infrared (785 nm) we observe a 2-fold larger SERS enhancement (1.3 x 10(4)) for excitation parallel to the nanocavities and detect the onset of SERS amplification for excitation polarization parallel to the nanowires long axis. Polarization-sensitive SNOM in the near-infrared (830 nm) enables the correlation of the scattered intensity with the sample morphology at the local scale. We demonstrate that the field enhancement stems from the wire-to-wire nanocavity regions when the excitation field is polarized parallel to the wire-to-wire nanocavity, while we observe more complex field confinement patterns related to the partially inhomogeneous morphology of the substrate when the polarization is parallel to the nanowires long axis. Our experiments strongly suggest IBS-fabricated nanowires as novel substrates for plasmon-enhanced spectroscopies.

In this paper, light absorption enhancement in thin film solar cell (SC) is reported and analyzed. The suggested design is based on a nanostructured pattern that increases the diffuse scattered component of radiation and hence the absorption through the active layer. An ion beam sputtering (IBS) approach is used to texture large areas of the glass substrate with high aspect-ratio ripples in order to increase light scattering. Then, thin film SC supported on the textured glass is simulated and analyzed using 3D finite difference time domain (FDTD) method. The suggested SC can offer an ultimate efficiency of 19.26% with short circuit current of 15.76 mA/cm2 with an enhancement of 31.435% over the SC without texturing surface.

A gold nanowired grid polarizer is studied in the mid-IR range by means of spectroscopic Mueller matrix ellipsometry. This material is also an example of a so-called 2-dimensional hyperbolic metamaterial/metasurface, and produced by low-cost large area scalable manufacturing techniques. We present the IR spectroscopic Mueller matrix optical response of such sample for a full azimuthal rotation. It is observed strong in-plane anisotropy due to the gold wire grid. The main objective is to show a characterization methodology to reveal the complete polarimetric response over a large spectral range, providing information about the effective optical properties of the sample. Three different optical models are proposed that catch the main features of experimental data. The first one is based on the Rigorous Coupled-Wave Analysis (RCWA) assuming the profile of the sample to be periodic, second, a Generalized Effective Medium Approximation (G-EMA) assuming oriented gold ellipsoids aligned along the lines of the wire grid, and third, a biaxial dispersion model. Experimental data is compared with simulated data obtained from the three optical models and a comparative analysis between them is presented. The different models allow to retrieve information on the characteristic dimensions of the nanowires, and also to obtain the two in-plane components of the effective dielectric tensor of the nanostructured layer. The tensor component parallel to the nanowires shows a metallic response whereas the component perpendicular to them behaves as a transparent dielectric. Moreover, we have also shown that the nanowired grid behaves as a hyperbolic material.

Here we investigated the SH generation at the wavelength of 400 nm (pump laser at 800 nm, 120 fs pulses) of a “metasurface” composed by an alternation of GaAs nano-grooves and Au nanowires capping portions of flat GaAs. The nano-grooves depth and the Au nanowires thickness gradually vary across the sample. The samples are obtained by ion bombardment at glancing angle on a 150 nm Au mask evaporated on a GaAs plane wafer. The irradiation process erodes anisotropically the surface, creating Au nanowires and, at high ion dose, grooves in the underlying GaAs substrate (pattern transfer). The SHG measurements are performed for different pump linear polarization angle at different positions on the “metasurface” in order to explore the regions with optimal conditions for SHG efficiency. The pump polarization angle is scanned by rotating a half-wave retarder plate. While the output SH signal in reflection is analyzed by setting the polarizer in ‘s’ or ‘p’ configuration in front of the detector. The best polarization condition for SHG is obtained in the configuration where the pump and second harmonic fields are both ‘p’ polarized, and the experiments show a SH polarization dependence of the same symmetry of bulk GaAs. Thus, the presence of gold contributes only as field localization effect, but do not contributes directly as SH generator.

We have investigated the growth and stability of molecular ultra-thin films, consisting of rod-like semiconducting para-hexaphenyl (6P) molecules vapor deposited on ion beam modified TiO

We investigate the scattering properties of novel kinds of nano-textured substrates, fabricated in a self-organized fashion by defocused ion beam sputtering. These substrates provide strong and broadband scattering of light and can be useful for applications in thin-film solar cells. In particular, we characterize the transmitted light in terms of haze and angle-resolved scattering, and we compare our results with those obtained for the commonly employed Asahi-U texture. The results indicate that the novel substrate has better scattering properties compared to reference Asahi-U substrates. We observe super-Lambertian light scattering behavior in selected spectral and angular regions due to the peculiar morphology of the nano-textured interface, which combines high aspect ratio pseudo random structures with a one-dimensional periodic pattern. The enhancement of light absorption observed in a prototype thin film semiconductor absorber grown on nano-textured glass with respect to an Asahi-U substrate further confirms the superior light trapping properties of the novel substrate.

We have investigated the growth and stability of molecular ultra-thin films, consisting of rod-like semiconducting para-hexaphenyl (6P) molecules vapor deposited on ion beam modified TiO2(110) surfaces. The ion bombarded TiO2(110) surfaces served as growth templates exhibiting nm-scale anisotropic ripple patterns with controllable parameters, like ripple depth and length. In turn, by varying the ripple depth one can tailor the average local slope angle and the local step density/terrace width of the stepped surface. Here, we distinguish three types of substrates: shallow, medium, and deep rippled surfaces. On these substrates, 6P sub-monolayer deposition was carried out in ultra-high vacuum by organic molecular beam evaporation (OMBE) at room temperature leading to the formation of islands consisting of upright standing 6P molecules, which could be imaged by scanning electron microscopy and atomic force microscopy (AFM). It has been found that the local slope and terrace width of the TiO2 template strongly influences the stability of OMBE deposited 6P islands formed on the differently rippled substrates. This effect is demonstrated by means of tapping mode AFM, where an oscillating tip was used as a probe for testing the stability of the organic structures. We conclude that by increasing the local slope of the TiO2(110) surface the bonding strength between the nearest neighbor standing molecules is weakened due to the presence of vertical displacement in the molecular layer in correspondence to the TiO2 atomic step height.

Hyperbolic metamaterials use the concept of controlling the propagative modes through the engineering of the dispersion relation, and are considered highly promising to reach different meta-properties. Spectroscopic Mueller Matrix Ellipsometry with variable angle of incidence and full azimuthal rotation of the sample is a powerful optical technique to characterize both anisotropic and bi-anisotropic materials. We here discuss the experimentally extracted uniaxial and biaxial optical properties of two self-assembled plasmonic systems that appear to have the appropriate meta-dispersion relations. The metasurface was produced by oblique incidence angle ion beam sputtering of glass followed by shadow deposition of Au [1]. The second bulk metamaterial was a block-copolymer based self-assembled hyperbolic metamaterial of nanocomposites based on metal nanoparticles embedded in a self-assembled anisotropic polymer host, presenting a strong spectrally selective optical anisotropy [2]. The extracted effective dielectric functions and the resulting dispersion relations are presented.

We have studied the influence of anisotropic nanopatterns (ripples) on the adhesion and morphology of mouse neural stem cells (C17.2) on glass substrates using cell viability assay, optical microscopy and atomic force microscopy. The ripples were produced by defocused ion beam sputtering with inert Ar ions, which physically remove atoms from the surface at the energy of 800 eV. The ripple periodicity (∼200 nm) is comparable to the thickness of the cytoplasmatic microspikes (filopodia) which link the stem cells to the substrate. All methods show that the cell adhesion is significantly lowered compared to the same type of cells on flat glass surfaces. Furthermore, the AFM analysis reveals that the filopodia tend to be trapped parallel or perpendicular to the ripples, which limits the spreading of the stem cell on the rippled substrate. This opens the perspective of controlling the micro-adhesion of stem cells and the orientation of their filopodia by tuning the anisotropic substrate morphology without chemical reactions occurring at the surface.

The interaction of CO with structurally well-defined Pt x Ru y surface alloys supported on Ru(0 0 0 1) was investigated by thermal desorption spectroscopy and infrared reflection–absorption spectroscopy. The surface composition and the distribution of the surface atoms were controlled by high resolution scanning tunneling microscopy. On these surfaces, which have a nearly random distribution of the two surface species, the adsorption (and desorption) of CO is strongly modified compared to the pure elemental surfaces, by strain effects and electronic ligand effects. CO adsorbs exclusively in a linear configuration on Pt and Ru atoms for all surfaces investigated. The adsorption energy of CO is lowered on the alloy surfaces with respect to both Pt(1 1 1) and Ru(0 0 0 1), similar as for pseudomorphic monolayer Pt films. For both Pt and Ru sites the adsorption strength decreases with increasing Pt concentration.

We present experimental results on simultaneous surface nanostructuring and optical activation of lithium fluoride crystals by 800 eV off-normal Ar + sputtering. Our data demonstrate that the formation of periodic nanostructures is accompanied by the efficient production of stable electronic defects, optically active in the green and red parts of the visible spectra, thus providing the possibility to conceive and fabricate advanced insulating substrates.

Starting from their discovery in 1991, carbon nanotubes have attracted a great attention, thanks to their peculiar mechanical, electrical and elastic properties that could be used to realize new devices in many different fields. For nanotechnology applications it is very important to be able to control not only shape and position but also alignment and orientation of carbon nanotubes, both during the growth and after it. Here we present preliminary results obtained by depositing carbon nanotubes (CNT) solutions on ion sputtered quartz substrates. Atomic force microscopy (AFM) images allow to study both CNTs positioning on the “ripples” generated by Ar+ sputtering on the SiO2 surface and their radial deformation induced by the “rough” surface. Work is now in progress to optimize the sputtering parameters and solution treatment (purification and functionalization) in order to get single CNTs regularly arranged on a patterned surface.

The smoothening process of nanometer-scale ripples grown on the (1 1 0) surface of silver is investigated using thermal energy He atom scattering. Morphological equilibration the corrugated surface is followed in real time in the temperature range between 205 and 230 K. The mean ripple wavelength, Λ , is observed to increase during surface recovery. To take this effect into account the decay time is assumed to scale as Λ 3 . Within this approximation the ripple amplitude is observed to decay linearly with time. The activation energy of the mechanism driving surface relaxation is estimated as (0.46 ± 0.02) eV. The underlying rate limiting process, i.e. adatom detachment from the open 〈0 0 1〉 step edges is evidenced.

We present a novel experimental technique devoted to the investigation of contact mechanics on mesoscopic scale. It consists of an atomic force microscope (AFM) equipped with custom-designed probes with integrated flat micrometric tips. Samples are normally compressed by the flat tips and load–displacement curves are acquired. The latter allow to investigate the mechanical response under a multi-asperity regime not accessible by conventional AFM. Preliminary results are reported for the contact mechanics of nanostructured carbon-based films having a self-affine fractal morphology.

The mechanism of oxygen incorporation in Ag is still poorly known. As recently demonstrated [Phys. Rev. B 63 (2001) R1404], oxygen adatoms removal by CO oxidation leaves the Ag(0 0 1) surface in a modified state in which oxygen segregation from the bulk and the formation of a surface oxide phase can be induced by further CO exposure. Here we show that the same channels, forming during CO oxidation and linking surface and subsurface sites, allow also for the migration of oxygen adatoms into the subsurface region. When dosing O2 on an Ag(1 0 0) surface, on which oxygen had been previously removed by CO oxidation, we observe indeed the formation of the same surface oxide phase produced by oxygen segregation. A characterisation of this phase by X-rays photoemission spectroscopy and high resolution electron energy loss spectroscopy is given, from which we deduce that it extends several layers deep into the volume. 2002 Elsevier Science B.V. All rights reserved.

Regular array of plasmonic nanoantennas (nanocrescents) can be easily produced by grazing evaporating gold on a self-ordered surface formed by hexagonal arrangements of polystyrene nanospheres, thus realising a hybrid plasmonic-photonics nanostructures (HPPN). By using second harmonic generation (SHG) technique we experimentally demonstrated that asymmetry in the shape of the nanoantennas induces an optical chiral response of the whole sample.

Here we report on the potentiality of the self-organised nanopatterning in view of broadband photon harvesting in thin film amorphous silicon (a-Si) solar cells. Self-organised pattern formation of glass, semiconductor and TCO interfaces is achieved recurring to low-energy Ion Beam Sputtering (IBS).

The submonolayer homoepitaxial growth on Ag(1 1 0) is studied by using a variable-temperature ultrahigh vacuum scanning tunneling microscope. The evolution of island density is studied as a function of temperature at given flux (≈0.0025 ML s −1 ) and coverage (0.16 ML) to evaluate the energy barriers and the binding energies for the in-channel and cross-channel diffusion. The experimental results are compared with kinetic Monte Carlo simulation.

CO dissociation on rhomboidal faceted nanopyramids, produced on Rh(110) by fine-tuning of ion irradiation conditions, has been studied by high resolution core-level spectroscopy. We find that this morphology presents a large efficiency towards CO dissociation, a process which is inhibited on flat (110) terraces. We also measured the reactivity of nanostructures bound by different artificial step distributions identifying the sites responsible for the molecular bond disruption in the undercoordinated (n=6) edges running along the [1 (1) over bar2] equivalent directions, with CO sitting in on-top configuration.

Understanding energy transfer processes at surfaces is an obliged step for a full description of gas–surface systems and many efforts have been devoted to both theoretical and experimental investigations of the dynamics of gas surface interaction, with particular attention to chemisorption, where chemical bonds are created (between the gas and the metal surface) and broken (the bond between atoms in the molecule, in case of dissociative chemisorption). [1]

Here we show the way to easily tune and engineer the optical response of hybrid structures composed by self ordered dielectric nanospheres partially covered by anisotropic plasmonic structures. The overall structure is a hybrid plasmonic-photonics nanostructure acting as a meta-surface witch morphology allows efficient and versatile light manipulation both for linear polarized and circular polarized fields in the visible and near infrared frequencies.

The dynamics of the dissociative adsorption of O 2 on Ag(001) were investigated with a supersonic molecular beam source and electron energy loss spectroscopy versus surface temperature. Contrary to the case of Ag(110) where dissociation occurs at the atomic terraces and has a high probability, for Ag(001) we find that only 0.44% of the adsorbed molecules dissociate at room temperature. An Arrhenius analysis indicates that the process is thermally activated and the activation energy coincides with the energy for generating kinks, which are thus identified as the active sites. The interplay between a local geometry similar to a (110) site and enhanced charge transfer to the antibonding molecular orbitals is responsible for the pronounced reactivity of such sites. Molecules adsorbed at (001) terrace sites instead desorb with a high probability.

Structural features and magnetic behaviour of TbPc2 thin films sublimated on LSMO and on cobalt surfaces have been investigated by synchrotron-based XNLD and XMCD techniques. Different orientation of the molecules is observed for the two substrates. No significant magnetic interaction with the ferromagnetic substrates is detected.

Here we present the measurements of the second harmonic generation (SHG) signal raised by self ordered dielectric nanospheres partially covered by thin (10nm) Au layer. The measurement were performed by studying the SHG efficiency in different polarization states of the light. In particular measurement performed with circular polarized light show the presence of chiral response of the nanospheres that is induced by the particular geometry of the metasurface.

Gold nanowires in general demonstrate very interesting plasmonic properties. Here, by applying the generalized Snell’s law introduced by F. Capasso in 2011, we study how the resonant behavior of the nanowires and their geometrical feature such as the radius of curvature can produce a bent in the propagation direction of a transmitted light beam. The measurements that were performed at a wavelength larger than the nanopatterned features reveal information on the meatusurface morphology.

Nanostructured glass substrates endowed with high aspect ratio one-dimensional corrugations are prepared by defocused ion beam erosion through a self-organized gold (Au) stencil mask. The shielding action of the stencil mask is amplified by co-deposition of gold atoms during ion bombardment. The resulting glass nanostructures enable broadband anti-reflection functionality and at the same time ensure a high efficiency for diffuse light scattering (Haze). It is demonstrated that the patterned glass substrates exhibit a better photon harvesting than the flat glass substrate in p-i-n type thin film a-Si:H solar cells. © 2013 IOP Publishing Ltd.

We have investigated the interaction of oxygen with Ag(111) by using a supersonic molecular beam in the impact energy range 93–800 meV. At 105 K, contrary to the results of Carley et al. [Surf. Sci. 238 (1990) L467], we find no evidence for O 2 adsorption even after very high O 2 exposures (∼ 25000 L) indicating that for a clean surface the sticking probability S is lower than 6 × 10 −7 for the whole impact energy range. At room temperature dissociative oxygen adsorption occurs at E i = 0.80 eV, with S ≈ 9 × 10 −7 . The data show however evidence that the adsorption process is mediated also in this case by adsorbed OH so that S is even smaller for the clean surface.

Resonant metallic nanostructures, located at the interface between two dielectrics, can produce abrupt phase discontinuities on propagating light that will be anomalously refracted by following the generalized Snell’s law. In this work, we show evidence of anomalous refraction arising when such an interface is nano-patterned with self-assembled bent gold nano-wires having sub-wavelength periodicity.

We review results relative to the formation of regular nanoscale patterns on metal substrates exposed to defocused ion beam irradiation. Particular emphasis is placed on work which demonstrates the possibility of controllably modifying chemico-physical properties of the material by tailoring the nanoscale morphology during IBS patterning. Starting from the well-established results found on single-crystal model systems, we show how the controlled modification of the atomic step termination can deeply affect chemical reactivity or magnetic anisotropy. We then look in greater detail at the more recent attempts focused on the extension of IBS patterning on supported polycrystalline metal films, a promising class of systems in view of potential applications. A modification of the functional properties of metal films can also be obtained by forcing a shape anisotropy of the nanostructures. The modification of the optical response of polycrystalline metal nanowires supported on anisotropic templates produced by IBS provides a clear example of this.

With a quartz crystal microbalance (QCM) we have studied the nanofriction of neon and other simple gases deposited on lead at low temperature. Special care has been paid to the investigation of some artifacts in the QCM response encountered after the initial cooldown. Extensive results obtained with QCMs that have been thermally annealed confirm that Ne films slide on Pb below 10 K. However, no extra dissipation is observed when the Pb electrode is driven either magnetically or thermally into the metallic state. This means that the electronic contribution to friction is negligible for this system, probably, because of the small polarizability of Ne atoms. More polarizable adsorbates like N${}_{2}$, Kr, and Xe are instead found to be completely pinned to Pb below 10 K.

Here we report the experimental observation of circular dichroism in the second-harmonic field (800--400 nm conversion) generated by self-organized gold nanowire arrays with subwavelength periodicity (160 nm). Such circular dichroism, raised by a nonlinear optical extrinsic chirality, is the evident signature of the sample morphology. It arises from the curvature of the self-assembled wires, producing a lack of symmetry at oblique incidence. The results were compared, both in the optical linear and nonlinear regime, with a reference sample composed of straight wires. Despite the weak extrinsic optical chirality of our samples (not observable by our optical linear measurements), high visibility (more than 50%) was obtained in the second-harmonic generated field.

With a quartz crystal microbalance technique we have studied the nanofriction of neon monolayers deposited on a lead surface at a temperature around 7 K. Unlike heavier adsorbates, Ne is found to systematically slide at such low temperatures without any evidence of pinning. The crossing of the Pb superconducting-metal transition is not accompanied by any change in dissipation, suggesting that the electronic contribution to friction is negligible for this system.

The controlled production of nanostructures endowed with well-selected shapes and reduced dimensionality represents a multidisciplinary key activity in nanotechnology. In particular, a great effort is currently oriented at the development of metal nanoparticle arrays in order to exploit the strong field-enhancement effects associated with the excitation of localized surface plasmon resonances. Here we demonstrate that ion-beam sputtering can be successfully employed to convert a polycrystalline metal film into a disconnected array of nanowires supported on a flat dielectric substrate. The nanowire arrays exhibit spectrally selective dichroic absorption due to the excitation of localized plasmon oscillations. The possibility to tailor the broadband plasmonic response has been demonstrated by finely tuning the morphological parameters of the arrays.

With a quartz-crystal microbalance technique we have studied the nanofriction of Ne monolayers at temperatures below 6.5 K and in ultrahigh-vacuum conditions deposited on metallic surfaces plated with heavy rare-gases multilayers. Covering the electrode with one layer of Kr or Xe increases the slippage of a Ne monolayer by a factor close to 3. Such a behavior has been observed with smooth lead electrodes as well as with rougher gold ones. The lubrication effect does not improve with thicker overlayers.

The self-organized formation of high aspect ratio dielectric nanostructures can be guided and sped-up recurring to a sacrificial metal film during ion beam sputtering. Following ion irradiation, the metal film evolves into a disconnected array of laterally ordered nanowires, which guide etching of the dielectric substrate. While the amplification rate of large scale features can be described simply in terms of the ratio of the sputtering yields of substrate and film, for small scale features the amplification rate depends on the interplay and lateral range of the smoothing and erosive mechanisms of the two materials.

Nano-patterned metal surfaces on dielectric substrates are become very important in nanoscale optical devices such as molecular sensors, second harmonic emitters, negative index materials. Among these, self-organised approaches are a promising alternative to the conventional lithographic or scanning lithography methods, since allow low cost patterning of large macroscopic surface in a single step event. The possibility to construct tailored artificial nanostructures by acting on simple experimental parameters opens new exciting possibilities in the nanoscale technology. In this work we explored the second harmonic emission properties in transmission of self-organized gold nanowires on dielectric substrates. Second harmonic emission from thin metal surfaces is limited by several constrains: for example the emission is forbidden at normal incidence and the emission is always polarized along the plane of incidence of the pumping light. In our samples selected morphology allows to overcome such constrains leading to high emission at normal incidence, polarization of the emission guided by the wires orientation. The angular dependence of the generation efficiency was measured on test samples whose thicknesses of the wires range from 5 nm to 40 nm. The efficiency results of a value larger with respect to samples with equivalent thickness and different morphology.

Here we report the second harmonic emission properties of self-organized gold nanowires arrays supported on dielectric substrates with a sub-wavelength periodic pattern. The peculiar morphology of the nanowires, which are locally tilted with respect to the average plane of the substrate, allows to generate maximum second harmonic signal at normal incidence with a polarization direction driven by the orientation of the wires (perpendicular to the wires). The generation efficiency was increased by tailoring the growth process in order to tune the metal plasmon resonance close to the pump field frequency and also by increasing the local tilt of the nanowires.

A thin metal film can exist in a metastable state with respect to breaking into small clusters. In this paper we report on grazing incidence small-angle x-ray scattering studies carried out in situ during the annealing of thin Ni films, between 2 and 10 nm thick, deposited on an amorphous ${\text{SiO}}_{2}$ substrate. Our results show the presence of two different regimes which depend on the initial film thickness. For thicknesses less than 5 nm the annealing results in the formation of small, compact clusters on top of a residual Ni wetting layer. For thicknesses greater than 5 nm the film breaks into large, well-separated clusters and the substrate shows an uncovered clean surface.

The leak devices most frequently used to calibrate leak-detection instruments are permeation leaks. These devices are very sensitive to temperature and can only be used with helium. The physical-leak types that could overcome this limits are prone to clog and their minimum size (about 1 μm) limits their applicability in the lowest flow range. Here, the authors propose a fabrication technique by means of focused-ion beam with which, in suitable materials, they are able to produce nanometer orifices. These devices [Universita degli Studi di Genova, Italian Patent No., TO2008A000683 (18 September 2008)] work in the molecular-flow regime up to atmospheric pressure and do not clog. Other advantageous characteristics are the possibility of obtaining leak rates in the range equal to those of the permeation type and the linear dependence of the throughput on the inlet pressure.

Here we report on the development of an unconventional approach for the physical synthesis of laterally ordered self-organized arrays of metallic nanowires supported on nanostructured dielectric templates. The method, based on a combination of nanoscale patterning of the glass substrate by ion beam sputtering with shadow deposition of the metal nanoparticles, provides a viable alternative to time consuming serial nanopatterning approaches. Far-field optical characterization demonstrates that the nanowire arrays exhibit tunable anisotropic properties in the visible range due to the excitation of localized plasmon resonances.

We report on the self-organized patterning of polycrystalline metal films supported on dielectric substrates using defocused Ar{sup +} ion-beam sputtering at glancing incidence. The data demonstrate that a nonflat initial surface morphology does plays a critical role in triggering self-organization during the early stages, where the distribution of polycrystalline grains initially imposes a nonstochastic spatial modulation of the ion impact sites. A crossover to the conventional erosive regime observed for single crystals sets in at longer sputtering times. Surprisingly, the vertical and lateral modulation of the pristine surface profile of the nonflat films results in a substantial reduction in the ion dose required for the formation of the nanoscale patterns, in comparison to the case of an initially flat film.