Catalytic synthesis of graphene occurs when methane reacts with cubic SiC nanopowder at 1000-1200K. The composite, created under relatively mild experimental conditions, consists primarily of 30-40 nm diameter cylinders with aspect ratios near unity whose walls are composed of 10-20 layers of graphene surrounding nano-SiC particles. Sputtering by electron irradiation sequentially removes the graphene shells thus exposing the SiC cores. Electron as well as X-ray diffraction studies reveal the highly crystalline nature of the graphene shells which constitute 90 mol% of the composites. Raman data support a model involving growth of graphene on carbon rather than on silicon terminated SiC.

We demonstrate that drop cast films of colloidal nanocrystals containing excess surfactants develop aggregation over several weeks after solvent evaporation. Fingered structures, typical of diffusion-limited aggregation, are created because of the residual mobility that nanocrystals retain in the film. We are able to control the aggregation through the concentration of surfactant molecules and the drying temperature of the films.

Using a hybrid computational approach, we introduce A-like nanorods into a phaseseparating AB blend, which has 45/55 composition. In the absence of the rods, the minority A phase forms droplets in the matrix of B. With the addition of N = 670 rods that interact solely through a short range repulsive interaction (mimicking the steric stabilization provided by a coating of A ligands), the mixture retains this droplet morphology. When, however, we add an effective attraction between the sterically stabilized rods, the nanoparticles form extensive networks in the A phase, which can form a continuous phase. In addition to altering the morphology of the mixture, the attractive interaction influences the rate of domain growth. In particular, at early times, the mutually attractive rods increase the growth rate of the domains in the early stage. At late times, the domain growth crosses over to a slow growth regime. Our findings demonstrate that the morphology and coarsening of a rod-filled blend can be controlled by varying the rod-rod interaction and hence, provides guidelines for tailoring the electrical and mechanical properties of the nanocomposites.

A novel vertical nanoporous structure is reported as a starting point for the fabrication of a fully-surround gate field effect transistor (FET) based on well-ordered nanostructures array. The proposed porous stacking is perfectly suited both for the collective organization of high density (up to 1011.cm-2) arrays of nanostructures like nanowires (NWs) or nanotubes (NTs), as with calibrated diameters (during growth), as well as for easing the Source, Gate, and Drain electrodes connections for individual or groups of nanostructures. Moreover the unique fully-surround gate architecture enables a quasi-ideal coupling between the gate and the channel, theoretically leading to improved devices performance and reduced global power consumption.

In this paper we describe the main steps for this versatile and lithography-free technique to fabricate a multi-layer porous template down to the nanometer scale, as well as the first nanostructures (carbon NTs) growth attempts inside such functional template. We highlight the fact that the proposed porous structure may acts as a passive template for the one-dimensional nanomaterials growth as well as an active element in the future device.

The proposed approach is in line with bottom-up fabrication approach to provide smaller devices, and is fully-compatible with classical processes used in the silicon industry.

In this work, dot and anti-dot structures in Co, Ni, Ni80Fe20, Fe50Pd50, Fe73.5Cu1Nb3Si13.5B9 and Fe78B13Si9 thin films have been produced by means of nanosphere lithography. Two multi-step processes have been followed and will be here described. The first one directly exploits polystyrene nanosheres (PN) as a mask to fabricate arrays of magnetic nanoholes and dots. In the second case, the nanospheres are used to design a polymeric mask of a photoresist subsequently used to pattern a magnetic nanostructure on a film. Advantages and disadvantages of the two lithographical techniques will be here highlighted. In both processes, the dimension and mutual distance of the patterns are dependent on the starting PN diameter (in the interval 500-800 nm). Samples microstructure has been studied by means of SEM and AFM microscopy. Room-temperature hysteresis loops have been measured by an AGFM (Alternating Gradient Field Magnetometer). MFM microscopy has been exploited to study the magnetic domain pattern. All produced systems have been observed to display tunable microstructure and, consequently, various magnetic properties for application.

Dislocation mediated mechanism of surface deformation due to localized stress and strain concentration near a void could give an explanation of field enhancement in conditions relevant to the design of rf accelerating structures of the Compact Linear Collider (CLIC). We have performed molecular dynamics simulations of a near surface void in copper under thermal stressing conditions. The von Mises strain was observed to be concentrated near the void surface with the maximum strain concentration factor of 1.9. To observe the activated slip-planes, we exaggerated the compressive stress to the extent that the dislocations were nucleated on the void surface at sites where von Mises strain was largest. Void depth and size were found to affect the dislocation nucleation. The nucleation was easier for larger voids and for voids which were closer to the surface.

A multisite lattice-gas (msLG) model with realistic and precise surface diffusion kinetics is applied to provide a reliable description of the initial stages of non-equilibrium self-growth of a NiAl alloy by simultaneous stoichiometric codeposition of Ni and Al on the NiAl(110) surface. Deposition at 300 K produces intermixing but poor alloy ordering. Increasing temperature enhances alloy ordering to near perfection at 600 K, but island shapes remain un-equilibrated.

Various metal fluoride crystals were subjected to electron beam irradiation at 200 and 300 kV using transmission electron microscopy in order to study in-situ fabrication of 3D metal nanostructures. Lithium fluoride, cobalt fluoride and aluminum fluoride salt fragments were chemically reduced and transformed by the electron beam to the corresponding metals. Using live video recording we observe that LiF crystals decompose in a unique way different to all other metal-halides. Li diffuses rapidly out of the salt crystal and covers its surface and the surrounding C-support film to many microns distance, where at random positions nucleation, growth and annihilation of Li nanorods and some nanospheres is observable. Decomposition of CoF2 also involves non-local synthesis of Co nanoparticles, mostly facetted, however, these are stable, without annihiliation, and their positioning seems to follow some degree of self-organisation. AlF3 transforms locally to Al grains inside the irradiated area only, and grain growth occurs to sizes proportional to the beam intensity. Findings are discussed in terms of displacement energy differences between the materials.

With the aim of providing an easy and versatile method for realizing conductive polymer surfaces with controlled micro and nano-scale topographical cues patterning, we deposited a ultra-thin film of the conductive polymer poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) on a thermo-retractable polystyrene sheet. Biaxial and uniaxial micro and nano-wrinkles were formed with different features depending on clamping geometry during shrinking of the substrate upon heating. Homogeneous nano and micro-patterning of surface topography over large areas (several cm2) was obtained. The formed wrinkles were very robust and adhered strongly to the substrate because of their penetration into the soft substrate during the heat-shrink process. In the case of uniaxial wrinkles a very well aligned quasi-periodic structure is formed with different populations of wavelengths ranging from submicrometric to 10-20 μm, depending on PEDOT:PSS thickness. Surface topography, wrinkles amplitude and wavelength have been evaluated by means of SEM and AFM and the results have been related to sheet resistance as measured with a four point probe technique. The realized conductive surfaces can offer new opportunities in the field of cell stimulation and growth.

Penetration of a nanochannel mask by 190keV Co+ ions is tested for the purpose of achieving laterally modulated ion implantation into a SiO2 thin film on a Si substrate. A 2D-nanoporous membrane of anodic aluminum oxide (AAO) is chosen as the mask. Criteria and challenges for designing the mask are presented. Implantation experiments through a mask with pore diameter of 125 nm and inter-pore distance of 260 nm are carried out. Cross-sectional TEM (XTEM) is shown as an ideal tool to assess depth distribution and lateral distribution of implanted ions at the same time, complemented by Rutherford backscattering spectroscopy. Using energy dispersive x-ray spectroscopy linescans, a Co distribution with lateral modulation is found at 120 nm below the oxide surface. First experiments in converting the atomic distribution of Co to discrete nanoparticles by in-situ TEM annealing are presented.

PS-b-PEO block co-polymers have been reported to form cylindrical, lamellar, gyroidic, and supramolecular architectures due to several reasons: some of the reasons include the chemical incompatibility between the lipophilic and lipophobic covalently cross-linked blocks resulting in a high Flory-Huggins interaction parameter, the annealing solvent, and the interfacial boundary conditions between the substrate and the phase separating blocks. We report here for the first time on the spontaneous formation of nanopores and nanorings in PS-b-PEO block co-polymers. The mean size and depth of the pores are about 150nm and 40nm, respectively, while the pores occur randomly placed in clusters of about 2-5 pores. The pore clusters leave behind a breath-like architecture replicated by the phase separating block co-polymer. These breath architectures, in the shape of nanorings, are formed during the initial period of phase separation and do not disappear after phase separation has been achieved, leaving behind a PS-enriched circular framework. The diameter of the nanorings is in the 200-700nm range, as measured from AFM phase and height images. This range falls within the reported size of water droplets forming breath structures on polymer films. The resulting nanoarchitectured materials could find potential applications where biocompatibility and water permeability of the PEO block within the nanopores is desirable. In addition, the slightly elevated nanorings could also provide semi-enclosed barriers that can serve as micro/nano-enclosed cell and tissue cultures.

We investigate the electronic properties of InAs/GaAs quantum rings (QRs) in a magnetic field using an original effective potential model based on a single band kp-approximation with an energy dependent effective mass. We used two sets of geometrical parameters for the selfassembled QRs. The first is the experimentally proposed geometry; the second follows from the oscillator model due to the relation between the model parameters and the real sizes of the quantum objects. The energy of an electron in a magnetic field, calculated for each of the geometries, is compared with C-V experimental data. We show that the results of the calculation obtained for the second geometry fit the experimental data rather well. Interpretation of the recent C-V data given by W. Lei et al. (Appl. Phys. Lett. 96 (2010) 033111) on the basis of the oscillator model is discussed.

The effect of Sb on the formation of Ge nano islands in Si by means of molecular beam epitaxy is reported. We observe in the Ge/Si(100) system a non-monotonic dependence of the Stranski-Krastanov critical thickness of Ge islands formation on the adsorbed Sb amount. Dome- and hut-shaped Ge islands are replaced with the pyramids, when Ge is deposited on the Sb-covered Si(100) surface. The Sb-mediated conservation of the shape of Ge islands during embedding them in Si is shown. We assume that the decrease of the surface diffusion of Si and Ge ad-atoms causes these effects.

Stepped Si(100) surfaces exhibit alternating stiff SA and meandering SB steps, and thus constitute a so-called AB-vicinal surface. Both growth by Molecular Beam Epitaxy (MBE) or Chemical Vapor Deposition (CVD), and erosion by ion sputtering or chemical etching, induce step pairing, although different factors contribute. In addition, more complex pattern formation often occurs during step train motion. We synthesize recent developments in modeling of these processes ranging from ab-initio electronic structure approaches for key surface energetics, to atomistic lattice-gas modeling, to coarse-grained sharp-interface (front-tracking) and smeared-interface (phase-field) step dynamics approaches. We briefly describe development of new formalisms related to coarse-grained approaches, as well as selected results for step pairing.

We present here a report on a role of initial nitridation of Si(111) surface on GaN nanorod growth. High quality wurtzite GaN nanorods are grown by Molecular Beam Epitaxy on bare Si(111)-7x7, crystalline and amorphous silicon nitride at 750oC, under nitrogen rich conditions. Using in-situ reflection high energy electron diffraction and ex-situ X-ray photoelectron spectroscopy, field emission scanning electron microscopy and photoluminescence, the structural and chemical properties are monitored. In the first part of the study, we have optimized the conditions of the N2* RF plasma, for formation of crystalline and amorphous silicon nitride on Si(111)-7x7 surface. While in the second part, GaN nanorods are grown on clean and these modified Si(111) substrates. Anisotropic spots are observed by RHEED for GaN grown on clean Si and on the amorphous silicon nitride, while circular, sharp and intense RHEED spots have been observed for GaN grown on crystalline Si3N4. FESEM results show nanorod growth in all the three different conditions. However, GaN nanorods grown on crystalline Si3N4 surface are observed to be self aligned and oriented along <0001> direction, while those grown on amorphous silicon nitride and bare Si(111) surfaces show great disorder increasing, respectively. Overall, the results clearly demonstrate that high quality of dense and self aligned c-oriented GaN nanorods can be formed on Si(111) surface by modifying it by appropriate nitridation.