The method of molecular-dynamics is employed to simulate and investigate the deformation of metallic nanowires under tensile strain. The interactions between metallic atoms are calculated by using the embedded-atom method potential. A model nanowire is preliminarily equilibrated at a specified temperature. Then, the uniform uniaxial extension of the nanowire is performed. The thinning process of a metallic nanowire is observed in the sequential snapshots of its morphological change.

We have demonstrated the fabrication of perforated thin films (PTFs), comprised of thin coatings perforated with unusual pore shapes such as helices or chevrons. PTFs are fabricated using a template of nanohelices or nanochevrons produced using the Glancing Angle Deposition (GLAD) technique. PTFs can be produced by filling GLAD films with a variety of substances, etching back the coating to reveal the tips of the helices or chevrons, and etching out the template film. A process for fabricating nickel PTFs has been developed, and a nickel PTF of helical pores with nominal diameters of 100nm has been produced.

Carbon nanotubes (CNTs) offer great potential for advanced sensing devices due to their unique electronic transport properties. However, a significant obstacle to the realization of practical CNT devices is the formation of controlled, reliable and reproducible CNT to metallic contacts. In this work, a procedure for the deposition and alignment of CNTs onto metallic electrodes using chemically functionalized lithographic patterns is reported. This method uses photo and electron beam lithography to pattern simple Cr/Au thin film circuits on oxidized Si substrates. The circuits are then re-patterned with a self-assembled monolayer (SAM) of 3-aminopropyltriethoxysilane (APTES) to specify desired CNT locations between electrodes. The application of an electric field to the metallic contacts during the deposition of solution suspended single walled CNTs causes alignment of the CNTs in the field direction. This method consistently produces aligned CNTs in the defined locations.

Conventional, broad-area, ion implantation has been combined with unconventional masking to create 2-D geometrical patterns of amorphization in single crystals, with selectable motifs. The patterns are fully developed by use of selective etching. Two examples are discussed. In the first example, a self-assembled array (with lattice spacing ∼1 μm) of silica spheres is used as an implant mask over InP. The variation of the mask thickness created by the sphere geometry modulates the implantation depth in a periodic fashion, which is subsequently revealed after selective etching of the associated amorphized volumes. In the second example, nanochannel arrays in an alumina film are used as an implant mask to produce a hexagonal closed packed array of amorphized cylinders in InP and SrTiO3 substrates. The ion beam-amorphized regions of the substrate are then removed by selective chemical etching to achieve the full 3-D patterning of 55 nm diameter holes on a 100 nm lattice spacing.

Dielectric properties of single walled carbon nanotube assemblies were calculated with an effective medium approximation at frequencies from 200 MHz to 200 GHz. The model treats the carbon nanotubes as layered cylinders, each with a core, a graphene layer and an outer layer, to investigate the dielectric properties of coated and filled nanotubes. The graphene and metal layer properties were modeled with a Drude approximation based on literature data. A generalized Bruggeman model was then used to determine the macroscopic behavior of the modified carbon nanotubes in a composite structure as a function of volume fraction, frequency, and aspect ratio. The depolarization factors in this model were scaled by the normalized effective permittivity to better account for percolation behavior. The model showed a wide variety of frequency dependent dielectric properties. Uncoated tubes were calculated to form highly conductive materials at volume fractions of just a few percent and metal-coated tubes enhanced the conductivity by an order of magnitude. Calculations of nanotubes with insulating coatings showed that high dielectric constants with moderate to low dielectric loss were possible.

Large-field ion-optics has been developed for reduction printing. Sub-100nm ion projection direct-structuring (IPDS) of patterned magnetic media discs has been demonstrated, extending over 17mm diameter exposure fields, in a single exposure. First results of IPDS patterning of nanocomposite resist material are presented. Information about a novel 200x reduction projection focused ion multi-beam (PROFIB) tool development is provided. Further IPDS nanotechnology applications are discussed.

The cobalt thin films are grown by D.C. magnetron sputtering as a function of the target-to-substrate distance, bias and power on both Si (100) and (111) substrates. The crystal structure and morphology of the thin films are characterized by 4-point probe, x-ray diffraction, scanning electron microscopy, transmission electron microscopy and atomic force microscopy. It is found that the cobalt crystal structure can be varied from HCP to FCC by varying the target to-substrate distance from 6 to 10 cm. The resistivity, roughness and the preferred orientation of the thin films are greatly affected by the substrate bias and power. The lowest resistivity of Co films is 9.8 -cm when deposited at the target to-substrate distance of 6cm, the applied power of 50W and the substrate bias of -75 volts. In addition, pyramid-like nanostructures with sharp tips are formed on the surface of the thin films when negative bias is applied. The faceted planes on the nanostructures depend on the resulting Co crystal structure while the size and density are determined by the growth parameters. The evolution of the surface nanostructures are systematically examined as a function of substrate bias and thin film thickness. The formation mechanism of the surface nanostructures is discussed in the paper.

Alkyl monolayers anchored covalently on silicon were prepared through the reaction between 1-alkenes and hydrogen-terminated silicon (111) surfaces. The 2D-patterning of the surface was done by local oxidation with an atomic force microscope (AFM) and 3D-molecular assemblies were fabricated by immobilization of molecules in a specific site of the patterned surface. The surfaces were anodized with a contact-mode AFM by applying a positive bias voltage to the surface with respect to the platinum-coated cantilever under ambient conditions, which resulted in nanometer-scale oxidation of surfaces. The anodized areas were etched and terminated with hydrogen atoms by NH4F solution, in which we could immobilize various molecules having C=C bonds. We put arylamine molecules to which organic dyes such as fluoroscein were anchored. The intensity of luminescence varied depending on dopant concentration of substrates. Luminescence was very weak on highly-doped silicon possibly due to effective energy transfer from dyes to substrates. The method demonstrated is one of the promising ways to fabricate 3D-assemblies of molecular-scale electronic devices with a stable interface on silicon.

The use of lasers to create intricate three-dimensional and buried structures [1] in photostructural glass has been well demonstrated at The Aerospace Corporation over the past four years. In these instances the glass used (Foturan™, made by the Schott Group) forms a silver nucleation sites on exposure to intense UV laser light via a two-photon process. Subsequent annealing causes a localized crystal growth to form a meta-silicate phase which can be etched in dilute hydrofluoric acid at rates of 20 to 50 times that of the unprocessed glass. We are now in the process of experimenting with another formulation of photosensitive glass, also pioneered by Corning Glass Works, that behaves differently during the bake process. In the second case, a photoexposure and bake process creates a silver-halide crystal and forms an adjacent void in the glass. A second photoexposure and bake allows for the migration of more silver into the void creating patterned formations of silver nano-wires [2]. Recent experiments with this type of glass have shown that the manipulation of the size and density of the embedded nano-wires as well as the overall pattern of the clusters can be controlled using direct-write exposure to laser processing.

Using the technique we have developed to grow porous anodic alumina (PAA) templates on the surface of silicon wafers, we have fabricated arrays of nanowires of thermoelectric materials. By this method we can control both (1) the in-plane geometry by the design of the template and the substrate, and (2) the out-of-plane dimension by control over the electrochemical nanowire growth process. We use several straightforward methods to make electrical contacts to the nanowires. Our transport studies show that both the structure of the nanowire and the contact region have a strong influence on the observed properties of the arrays.

Carbon nanotubes have been widely investigated as an essential component for fabricating nanoelectronic devices and for their numerous applications. We investigated the vertical alignment of single-walled carbon nanotubes (SWNTs) on chemically functionalized Si surfaces using chemical reactions between chemical groups in SWNTs and surfaces. For controlling the high selectivity of a specific chemical reaction, a pre-patterned 3-D nanostructure was used by using AFM anodization lithography for achieving the vertical alignment of SWNTs. To consider the subsequent chemical reaction with chemically modified Si surface, the carboxylic acid groups were converted into acid chloride groups followed by the reaction with chemically functionalized surfaces. The protruded structures on pre-patterned areas strongly suggest the vertically oriented SWNTs, and the distribution of the vertically aligned SWNTs becomes denser and their heights are longer with prolonged reaction time. The aspect ratio of SWNTs aligned on -OH functionalized surface is independent from the reaction time (H/W = 0.2). After random alignment of relatively shorter nanotubes on the substrate, their bundle size increases with increasing the reaction time due to strong van der Waals interaction between the lateral sides of nanotubes described as ‘nucleation growth’. Longer tubes get also adsorbed on the surface by increase in the bundle size and nanotube length, simultaneously. Based on the chemical reactions of the modified SWNTs with functionalized surfaces, selective attachments of SWNTs were carried out onto pre-patterned surfaces. Detailed characterization of aligned SWNTs will be discussed.

Our simulations predict that boron-nitride (BN) doping in carbon nanotubes can greatly improve the field emission properties of these systems. The intrinsic electric field associated with the polarity of the B-N bond enhances the emitted current density through a reduction of the work function at the tip. Using a combination of real-space and plane-wave ab initio methods, we show that this effect is present in both coaxial (BN@C) and linear (BN/C) nanotubular assemblies. While in the coaxial geometry the improvement amounts to a factor of five, the current density is predicted to increase by up to two orders of magnitude in BN/C superlattices.

The use of photons to create intricate three-dimensional and buried structures [1] in photo-structurable glass has been well demonstrated at several institutions [2]. In these instances the glass used whether it be Foturan™, made by the Schott Group or a similar product made by Corning Glass, forms a silver nucleation sites on exposure to intense UV laser light via a two-photon process. Subsequent annealing causes a localized crystal growth to form a meta-silicate phase which can be etched in dilute hydrofluoric acid at rates of 20 to 50 times that of the unprocessed glass. The same formulation of glass can be “exposed” using a particle beam to create the nucleation site. In the case of particle beam exposure, experiments have shown that the mechanisms that cause this initial nucleation and eventual stochiometric transformation, after annealing, depend largely on the beam energy.

Self-organized ZnO nanosize islands on thermally grown SiO2 layers on Si (111) with low-dimensional quantum characteristics were realized by metalorganic chemical vapor deposition. Investigation by atomic force microscopy showed that the density and size of the ZnO nanosize islands were changed by the growth conditions. In macroscopic photoluminescence measurements at 10 K using a 325 nm He-Cd laser, we observed the broad spectra with band tails, which were located at the higher energy with respect to band edge emission of ZnO thin films with the free exciton emission located at about 3.38 eV. These results indicate that these ZnO nanosize islands have low-dimensional quantum effect characteristics.

Nanoporous composite films of multi-walled carbon nanotubes (MWNTs) and either polypyrrole (PPy) or poly(3-methylthiophene) (P3MeT) were grown using an electrochemical polymerization technique in which the nanotubes and conducting polymer were deposited simultaneously. The concentration and dispersion of MWNTs in the polymerization electrolyte was found to have a significant effect on the thickness of polymer coated on each MWNT and hence the loading of MWNTs in the films produced. It has been shown that for an increasing concentration of MWNTs in the polymerization electrolyte, the thickness of polymer coated on each MWNT decreases. This relationship made it possible to minimize ionic diffusion distances within the nanoporous MWNT-PPy films produced, reducing their electrical and ionic resistance and increasing their capacitance relative to similarly prepared pure PPy films.

In this paper we are proposing the synthesis of iron and cobalt nanoalloys via the codecomposition of iron and cobalt carbonyl precursors in the presence of polystyrene as the surface stabilizing agent. In order to form iron-cobalt nanoalloys with no preferential aggregation of metal atoms resulting in phase segregation, the decomposition kinetics of the iron pentacarbonyl and dicobalt octacarbonyl precursors had to be firmly established. The kinetics of cobalt cluster formation has been thoroughly investigated, but data for iron pentacarbonyl decomposition is relatively scarce. To fully understand the formation of the iron nanoclusters, a kinetic study was performed by varying carbonyl concentrations and reaction media in order to establish reaction order and rate constants. Our results suggest this decomposition to be a higher order process (not first order as previously assumed), with a complicated intermediate mechanism, which has been postulated and experimentally verified. By using this kinetic data, we will be able to predict the necessary conditions for the creation of new in-situ iron-cobalt nanoalloys using carbonyl precursors.

The selective interaction of metal clusters with various polymers constitutes the basis for the self-assembly approach to the synthesis of organic-inorganic hybrid materials, that leads to the control of particle size, geometry and dispersion gradient. Metal particles were synthesized by the thermal decomposition of an organometallic precursor, in this case, iron pentacarbonyl, in the presence of a polymer matrix. Under the conditions utilized for these reactions, the aggregation of the metallic clusters competed with the interactions between the growing metal fragments and the polymer matrix. The dominance of one reaction route as compared to the other, ultimately determined the equilibrium particle shape, size and distribution for each metal-polymer system. In this work, we attempted to analyze the formation of iron oxide nanoclusters in several structurally-distinct polymers, and developed a general mechanistic view to explain the characteristics of the polymer-metal oxide hybrid materials that were obtained.

We have succeeded to form three-dimensionally orientated nano-sized crystals in a Ni-P amorphous alloy under focused ion beam (FIB) irradiation. The FIB micro-fabrication was performed on an electroless deposited Ni-P amorphous alloy and thin films with a thickness of 100 nm were prepared. Transmission electron microscopy (TEM) observation for irradiated areas revealed the formation of crystallographically orientated nano-sized crystals (NCs) in the irradiated region. The grain size of NCs was less than 10 nm in diameter. Electron diffraction analysis showed that the formed NCs have a face-centered-cubic (f.c.c.) structure and the following orientation relationships among the specimen, the NCs and the FIB direction: irradiated plane // {111}f.c.c. and ion beam direction // <110>f.c.c..

Certain classes of three dimensional nanostructures can be fabricated by contact printing patterns onto curved or non-flat surfaces. This paper reviews some of our work that demonstrates this approach by using microcontact printing to form a range of three dimensional structures with feature sizes as small as 1–2 microns and it demonstrates their use in a variety of functional devices. We also describe a nanotransfer printing technique with operational characteristics that are similar to those of microcontact printing but which enables nanometer resolution. High resolution replica molding techniques provide a method for producing copies of some of these printed structures.

FePtCu nanoparticles with varying composition were synthesized by chemical solution-phase reduction of platinum and copper reagents and thermal decomposition of iron pentacarbonyl in the presence of oleic acid and oleyl amine stabilizers. As prepared the particles had fcc structure with an average diameter of 3.5 nm and were superparamagnetic. The particles were well dispersed in hydrocarbon solvents and could be self-assembled into two or three dimensions particles arrays with a variety of close-packing arrangements. Heat-treatment of the self-assembled films at temperatures above 550°C transformed the particles from the fcc to the L10 phase, giving in-plane coercivities as high as 9000 Oe. X-ray diffraction revealed that the Cu remained in the annealed FePtCu films and the presence of an extra peak, indicated a second phase was present. Consistent with one or more phases, the magnetic hysteresis curves could be decomposed into a hard component (Hc > 5,000 Oe) and a soft component (Hc < 2,000 Oe). Unlike our earlier results for Ag in FePt, adding Cu to FePt did not lower the temperature required for phase transformation from the fcc to the fct L10 phase.