A deposition method based on inkjet printing technology and conductive double-wall carbon nanotubes (DWNT) suspension is, hereby, presented. The approach exploits the selective transfer capabilities offered by the inkjet printing process and the excellent conductive characteristics of the available DWNTs, in order to realize microelectronic interconnects of arbitrary patter and given electrical properties. The DWNTs are prepared by CCVD process, oxidized and dispersed in ethylene-glycol (EG) and in water solution. The DWNTs lines are fabricated on tests structures and then characterized through impedance and current-voltage measurements. 400 μm long and 90 μm wide transmission lines have been printed by varying the number of overwrites for given DWNT density. The results confirm that the DC resistance of DWNTs lines can be changed according to the number of overwrites and that the lines preserve ohmic characteristics up to 100 MHz.

We have fabricated sub-100 nm triangles NiFe triangle arrays using NSL and the MOKE measurement and micromagnetic simulations were carried out to investigate the reversal mechanism of the arrays. Enhancement of coercivity compared to the thin film was observed in all the three arrays but in different degree from the MOKE measurement. With the increase of the lateral size of the triangle, the effect of the coercivity enhancing decreases. Micromagnetic simulation shows that instead of domain wall nucleation and annihilation in the thin film, the reversal mechanism of the 45 and 80 nm triangles is dominated by the coherent rotation. While in the 100 nm triangle, the magnetic reversal takes place via forming and reversing a V like sate.

Carbon nanotubes are attractive candidates for electron field-emitters due to their high aspect ratio, mechanical stability, and electrical conductivity. It has previously been shown that an electron beam hitting the tip of a carbon nanotube biased near the threshold of field-emission can stimulate the emission of a large number of electrons from the nanotube tip. Here we report on similar experiments on arrays of free-standing multi-walled carbon nanotubes (nanotube forests) interacting with a scanning electron microscope's primary beam. Electron gains of up to 19,000 were obtained. This can enable applications such as electron detection and multiplication, and vacuum transistors.

We present the experimental results for the first known molecular beam epitaxy (MBE) growth of quasi-one-dimensional PbSe wires on technologically relevant silicon.In this work, we describe the growth and characterization of low-dimensional IV-VI semiconductors as they evolve from one-dimensional dot/dot-chains to one-dimensional structures on a self-organized template epitaxially grown on Si(110). In situ and ex situ characterization were performed at various stages throughout growth by reflection high energy electron diffraction, scanning electron microscopy, and non-contact atomic force microscopy. Initial growths resulted in some preferential alignment of the PbSe dot-chains parallel to the self-organized template in the [-110] direction. By reducing the substrate temperature and increasing the supplemental Se flux, the morphology of dot-chains extend into lengthened one-dimensional structures. This is an important milestone in the fabrication of PbSe quantum wires on technologically relevant silicon.

The successful implementation of silicon nanowire (NW)-based tunnel-field effect transistors (TFET) critically depends on gaining a clear insight into the quantitative carrier distribution inside such devices. Therefore, we have developed a method based on scanning spreading resistance microscopy (SSRM) which allows quantitative two-dimensional (2D) carrier profiling of fully integrated NW-based TFETs with 2 nm spatial resolution. The keys in our process are optimized NW cleaving and polishing steps, in-house fabricated diamond tips with ultra-high resolution, measurements in high-vacuum and a dedicated calibration procedure accounting for dopant dependant carrier mobilities.

Ensembles of indium phosphide nanowires were grown on amorphous quartz substrates and their optical properties were examined at various cryogenic temperatures. Complex dynamics result from the large areal densities, random orientation, combination of both zincblende and wurtzite phases, and the geometries of the nanowires. Those complex dynamics are discussed in relation to their effect on the temperature dependence of photoluminescence and Raman spectroscopy. Five peaks are found to exist in the photoluminescence spectra at low temperatures which are attributed to radiative recombinations associated with quantum confined zinc blende, quantum confined excitons in zinc blende, quantum confined wurtzite, excitons in bulk zinc blende and impurity states. An energy transfer mechanism between two types of radiative recombinations among the five is proposed to explain intensity variations and the temperature dependence of the PL peaks is discussed. The Raman spectra is observed to have peaks created by a combination of zinc blende and wurtzite vibrational modes which is explained by folding the phonon dispersion.

The strength and electrical conductivity of Carbon Nanotube (CNT) yarns is dramatically affected by the handling of the material after the nanotubes are produced. Our nanotube production process involving Chemical Vapor Deposition (CVD) using the floating catalyst method produces a mass of entangled bundles of single-walled nanotubes in a gas suspension. Simply collecting and spinning this material produces a yarn with strength and electrical conductivity far less than the properties of the individual nanotubes due to the poor alignment of the bundles on the microscopic scale. We have developed methods of aligning the CNT material that are analogous to the techniques used in the textile industry for spinning staple yarns, but modified to be appropriate for nano-scale material. The result is a dramatic improvement in strength and electrical conductivity of our CNT yarns.

Here we report a general route to prepare silica nanocomposite gels doped with fluorescent single walled carbon nanotubes (SWNT). We show that tetramethylorthosilicate (TMOS) vapors can be used to gel an aqueous suspension of surfactant-wrapped SWNT while maintaining fluorescence from the semiconducting nanotubes. The vapor phase silica process is performed at room temperature and is simple, reproducible, relatively quick, and requires no dilution of SWNT dispersions. However, exposure of aqueous SWNT suspensions to TMOS vapors resulted in an acidification of the suspension prior to gelation that caused a decrease in the emission signal from sodium dodecylsulfate (SDS) wrapped SWNT. We also show that although the SWNT are encapsulated in silica the emission signal from the encapsulated SWNT may be attenuated by exposing the nanocomposites to small aromatic molecules known to mitigate SWNT emission. These results demonstrate a new route for the preparation of highly luminescent SWNT/silica composite materials that are potentially useful for future sensing applications.

The influence of the type of alumina used as catalyst support on the evolution, activity, and lifetime of the catalyst during water-assisted CVD growth (or ‘supergrowth') of single-walled carbon nanotube (SWNT) carpets has been studied. The catalyst consisted of a thin Fe film supported on alumina films deposited by different methods: atomic layer deposition (ALD), e-beam, and magnetron sputtering. In order to fully understand the influence of the type of alumina on SWNT carpet growth, crystalline alumina (c-cut sapphire) and annealed alumina deposited by e-beam were also used as catalyst supports. The activity and lifetime of Fe catalyst during SWNT carpet growth showed a strong dependence on the type of alumina used as support. Fe supported on sputtered alumina (sputtered/Fe) showed the highest catalytic activity and lifetime, which was closely followed by e-beam/Fe while Fe supported on sapphire (sapphire/Fe) showed the least catalytic activity and lifetime. AFM, XPS depth profile, variable angle spectroscopic ellipsometry (VASE) studies revealed that the catalyst evolution and the porosity of the different alumina supports correlate with the lifetime and activity of the catalysts.

Molecular dynamics simulations of the flow of pressurised water through carbon nanotubes of chirality (9,0), (12,0), (15,0) and (18,0) have been undertaken at 298K with a water density of approximately 1240kg/m3. Results show that the rate of filling is least in the smallest diameter nanotube, but that there is less variation in the time taken to reach maximum occupancy. The water molecules are found to undergo restructuring due to their confinement, with detailed molecular arrangement dependent on CNT diameter. Enhanced rates of flow are shown for the (15,0) nanotube, highlighting the effect of nanotube diameter on confinement and thus on flow.

Single-crystalline rock-salt PbS nanowires (NWs) were synthesized using three different routes; the solvothermal, chemical vapor transport, and gas-phase substitution reaction of pre-grown CdS NWs. They were uniformly grown with the [100] or [110], [112] direction in a controlled manner. In the solvothermal growth, the oriented attachment of the octylamine (OA) ligands enables the NWs to be produced with a controlled morphology and growth direction. As the concentration of OA increases, the growth direction evolves from the [100] to the higher surface-energy [110] and [112] directions. In the synthesis involving chemical vapor transport and the substitution reaction, the use of a lower growth temperature causes the higher surface-energy growth direction to change from [100] to [110]. We fabricated field effect transistors using single PbS NW, which showed intrinsic p-type semiconductor characteristics for all three routes. For the PbS NW with a thinner oxide layer, the carrier mobility was measured to be as high as 10 cm2V−1s−1.

Atomic layer deposition (ALD) ZnO film as seed layer for growing aligned ZnO nanorods arrays is demonstrated. The effects of the deposition temperature and film thickness to the morphology of the ZnO nanorods are studied. The ALD is found to have its advantage over the conventional dip-coating method when being applied to three-dimensional (3D) substrates, as exemplified by the macroporous Si adn CNT arrays. As one example, the CNT-ZnO 3D hybrid nanostructures are obtained which might be useful for energy-related applications.

Pd is widely used in producing electrodes to single-walled carbon nanotubes (SWNT). However up to now its ability to form ohmic contacts to SWNTs was not employed in scanning probe microscopy (SPM). Here we present a study of SWNTs with Pd electrodes by SPM using Pd-coated tips. SWNTs were selectively grown on oxidized silicon substrates by low pressure CVD method. Pd electrodes were prepared to SWNTs to fabricate two terminal structures for SWNTs resistance measurements. It is shown that SPM Kelvin mode is a reliable technique for SWNT detection on insulating substrate. Contact potential difference between Pd electrode and SWNT is measured using the Kelvin mode.

We present growth of vertically aligned carbon nanotube (VCNT) on metal substrates such as Cu foils, Inconel 600 and stainless steel (SUS316L) using thermal chemical vapor deposition (TCVD) in order to get a low contact resistance at interface between CNT and substrates for future applications. The temperature range for VCNT growth was 700-775 °C and mixtures of acetylene, argon and hydrogen were used as processing gas. The tube length was controlled by growth time and temperature. Finally, we successfully grew the VCNT on Cu foils over 1 cm2 and confirmed the excellent electrical conductance which can be directly used as anodic electrode in lithium ion battery. On the other hand, the growth of VCNT on Inconel 600 or SUS316L sheets was carried out as purchased. These tubes are expected to be useful for field emission devices.

Large-area vertically aligned silicon nanowire (Si NW) arrays were synthesized with a controlled length (0.3 ˜ 9 μm) by the chemical etching of n-type silicon substrates. Upon their excitation using a fs Ti-sapphire laser pulse (800 nm), their THz emission intensity exhibits strong dependence on their length; the intensity increases sharply up to a length of 3 μm and then decreases slightly, due to the complete absorption of the optical pump power. The Raman scattering spectrum exhibits the same behavior as that of the THz emission. We suggest that the field enhancement by localized surface plasmons induces more efficient THz emission or Raman scattering for the longer Si NWs. The photocurrent measured in a photoelectrochemical cell showed consistently the length dependence with a maximum value at the length of 5 μm.

Nanoporous Anodic Alumina Films (NAAF) have been used for growing a lot of nanostructure functional materials. Of particular interest is the NAAF conversion into membranes (NAAM) with different highly controlled pore diameter and distribution to be used as templates and masks to grow a wide variety of nanomaterials. This work constitutes an approach to a review of our latest results regarding the use of NAAF and NAAM as templates in which II-VI semiconductor, functional oxides, hard materials and magnetic nanowires have been grown. The growth techniques and methods used include Isothermal Close Space Sublimation (ICSS), Magnetron Sputtering, electroplating and sol-gel. Ion Beam Irradiation (IBI) combined with different NAAM as masks has been also used for Titania substrates functionalization.

The mechanical properties of arrays of nominally vertically aligned carbon nanotubes, often referred to as turfs, have been measured using nanoindentation and the electrical properties have been measured using electrical contact resistance (ECR) nanoindentation. The elastic properties do not vary significantly between the top and the bottom of the same carbon nanotube turf. Within a single turf the lateral spatial variation is less than 10% when volumes of μm's are probed with the indenter, indicating that each turf can be treated mechanically as continuum on this scale. The electrical properties vary significantly within a single turf on the same scale. This suggests that the use of average mechanical properties for a given vertically aligned turf should be suitable for design purposes without the need to account for spatial variation in structure, and variations in mechanical properties on the micrometer scale are not dependent on spatially distinct defects. However, local contact behavior appears to dominate the electrical behavior on this same length scale.

This study presents a very cost effective template-based electrochemical technique to synthesize the nano heterojunctions of cadmium sulfide (CdS) and cadmium telluride (CdTe). SEM analysis revealed that the average length of CdS nanowires varied from 500 nm to 4 μm depending on the deposition time and voltage. Also, average diameter of the CdS nanowires ranged between 100 and 200 nm. The structures of CdS nanowires have been confirmed by XRD and EDX analysis. Photoelectrochemical performances of CdS nanowires revealed that there is a dramatic change in the photoelectrochemical performances with the change in deposition time and voltage. The maximum fill factor (FF) and power efficiency (η) of the CdS nanowires has been calculated as 45 % and 1.36 %, respectively. After the optimization of the CdS nanowire deposition conditions based on the PEC performance, CdTe nanostructures have been deposited on CdS nanowires at various deposition time. SEM analysis showed that CdTe nanostructures have a tendency to grow as nanoclusters. It was observed that the density and the average diameter of the clusters was a strong function of the deposition time. The average diameter of the CdTe nanoclusters after 9-hour deposition reached about 260 nm. The successful heterojunction of CdS nanowires with CdTe nanoclusters have been observed in the SEM analysis. It has been concluded that the PEC performances of the CdS nanowires improved significantly after CdTe deposition. The maximum η, obtained in this study is about 8.04 %. This is one of the highest efficiencies reported in the literature for the nanowire array photoelectrochemical cells.

Many challenges remain in the effort to realize the exceptional properties of carbon nanotubes (CNT) in composite materials. Here, we report on electrically conductive composites fabricated via infiltration of CNT-based aerogels. The ultra low-density, high conductivity, and extraordinary robustness of the CNT aerogels make them ideal scaffolds around which to create conductive composites. Infiltrating the aerogels with various insulating materials (e.g. epoxy and silica) resulted in composites with electrical conductivities over 1 Scm-1 with as little as 1 vol% nanotube content. The electrical conductivity observed in the composites was remarkably close to that of the CNT scaffold in all cases.

We propose a hydrogen assisted reactive ion etching method for generating nano-grass and nano-texturing of silicon substrates in desirable shapes and locations. The etching technique is based on sequential etching and passivation steps where a combination of three gases of H2, O2 and SF6 in the presence of RF plasma is exploited. Using this method it has been possible to realize high aspect ratio features on silicon substrates whereas by adjusting the etching parameters, it is possible to form texturing of silicon in desired places. This technique is highly programmable where the pressure, gas flows, plasma power and duration of each cycle can be preset to achieve desired features. The formation of nano-grass on the silicon surface improves its wetability both to water and oil spills.