Anodic Aluminum Oxide (AAO) is widely employed as a template for fabrication of nanowires and nanotubes due to its ability to generate self organized (SO), well ordered pore structures. We have developed a new aluminum pre-patterning technique to create well ordered nanopore arrays on thin films deposited on silicon substrates. We form patterns of thicker oxide on the surface via local oxidation process using a conducting Atomic Force Microscope (AFM) tip working in contact mode. Pores are forced to nucleate between the pre-oxidized regions during the anodization process. The relation between applied voltage and ordered interpore distance has been found to be linear for these supported thin films. However, the pore spacing is highly reduced compared to free standing foils. A new empiric law has been confirmed for a wide range of voltages, solution concentrations and different electrolytes, including oxalic and phosphoric acid. Our results show that pre-oxidation patterning is an alternative technique to achieve an ordered nanoporous template through the anodization process.

Indium phosphide (InP) nanowires (NWs) were grown by molecular beam epitaxy on various substrates including SrTiO3 (001), Si (001) and InP (111) at a growth temperature of 380°C. We used the Vapor Liquid Solid assisted method with Au as a metal catalyst. The composition of the catalyst particles and the crystalline structure of the nanowires were compared using reflection high energy electron diffraction, scanning electron microscopy and high resolution transmission electron microscope. It is found that InP nanowires grown onto InP and SrTiO3 substrates are structurally defects free with a wurtzite structure. On Si (001) substrates, the presence of stacking faults and cubic phase insertion along the growth direction is observed. The effect of the substrate on the composition of catalyst droplets and consequently on the crystalline quality of the nanowires is discussed for the conditions of nucleation and defect formation.

A simple and efficient approach for fabricating silicon nanopillar arrays with a high aspect ratio and controllable sidewall profiles has been developed by using holographic lithography and a novel single-step deep reactive ion etching. During the etching process, scalloping of the sidewalls can be avoided while reserving the high mask selectivity and high etching rate. Besides, the sidewall angle of resultant patterns can be adjusted by tuning the composition of the gas mixture of single-step DRIE process. We further fabricate a tapered silicon nanopillar array and observe its photonic bandgap property. We believe that the good optical performance of this tapered silicon nanopillar array realized by the proposed approach shows the promising of this process for various applications.

WO3 doped TiO2 nanotube(WO3-doped TNT) thin film was fabricated by anodizing the TiO2 nanotube (TNT) film in an NH4F electrolyte containing WO4- ions. The sample was characterized by Field Emission Scanning Electron Microscopy (FE-SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and UV–Vis diffuse reflectance spectroscopy (DRS). The results show that WO3 was successfully doped into TiO2 nanotubes and the absorption edge of WO3 doped TNT appeared to be red shifted. The photoelectrocatalytic (PEC) activity of WO3 doped TNT electrode was evaluated through the PEC degradation of aqueous Acid Blue 80. The experimental results demonstrated that the PEC degradation rate of WO3 doped TNT is increased by 48% and by 167% over that of non-doped TNT under UVA light irradiation and visible-light irradiation, respectively, at an applied potential of 1.54V. The degradation rates of WO3 doped TNT under photocatalytic (PC), electrochemical (EC), and PEC processes were compared. The results reveal the synergetic effect of PC and EC processes.

Silicon nanowires (Si NWs) were grown directly on transparent conductive oxide layers using a single pump down process in a plasma enhanced chemical vapour deposition (PECVD) system. Layers of ITO and SnO2 on glass substrates were exposed to a hydrogen plasma leading to the reduction of the oxide and to the agglomeration of the metal into catalyst droplets of a few tens of nanometers diameter. The diameter and the density of the nanowires depend on the catalysts droplets size and density, we studied step by step the evolution of the surface prior to and at the initial stage of the nanowire growth. The catalyst droplets size and distribution were essentially investigated through Scanning Electron Microscopy (SEM).

Nanowire arrays of PbTe were electrodeposited into porous alumina templates with 40nm pores. Citric acid was used as a complexing agent for HTeO2 + shifting the reduction potential of HTeO2 +/Te closer to that of Pb2+/Pb. Compositional analysis of the wires grown with the complexing agent show a 1:1 ratio of Pb:Te without any excess tellurium. Group III elements (In3+ and Tl+) can be added to the deposition solution and incorporated into the nanowires. It is proposed that indium incorporates into the PbTe lattice in a high energy interstitial site causing the lattice parameter to increase linearly with increasing indium incorporation. The addition of thallium to the deposition solution leads to a mixture of PbTe and TlTe nanowires. Upon annealing, the TlTe melts incongruently to Tl5Te3, which then alloys with PbTe, thereby increasing the lattice parameter.

The effects of hydrogen chloride (HCl) on the growth of silicon nanowires by Chemical Vapour Deposition are investigated. HCl is found to enable the growth of small diameter gold-catalyzed silicon nanowires while reducing the kink occurrence. Specific growth sequences are presented in order to obtain a one-to-one ratio of nanowire growth versus gold colloidal seed. Other growth sequences using HCl are illustrated but achieve mixed results concerning the nanowire structure and the surface state.

The electronic properties of carbon nanotubes are quite often drastically affected by the presence of defects that can develop during nanotube growth, processing or characterization too. Some of these defects such as pentagon-heptagon rings, substitutional impurities, vacancies and dislocations are of topological nature, and can sometimes create on-tube intramolecular junctions, as found by previous scanning tunnelling microscopy studies.

Our recent STM experiments reveal for the first time a much more complicated junction structure, a hybrid single-walled carbon nanotube consisting of a distinct coiled structure located between two straight segments, each of different helicity. We characterise the hybrid junction at the atomic level and describe its electronic behaviour that has important implications in the practical design of functional components for nanoelectronic applications.

Silica aerogels are ultra low-density, high surface area materials that are extremely good thermal insulators and have numerous technical applications. However, their mechanical properties are not ideal, as they are brittle and prone to shattering. Conversely, single-walled carbon nanotubes (SWNTs) and graphene-based materials, such as graphene oxide, have extremely high tensile strength and possess novel electronic properties. By introducing SWNTs or graphene-based materials into aerogel matrices, it is possible to produce composites with the desirable properties of both constituents. We have successfully dispersed SWNTs and graphene-based materials into silica gels. Subsequent supercritical drying results in monolithic low-density composites having improved mechanical properties. These nanocomposite aerogels have great potential for use in a wide range of applications.

ZnO nanowire (NW) has potential applications for transparent electrodes, gas sensors, nanoscale optoelectronic devices, piezoresponse force microscopy (PFM) and field effect transistors. In general, we have evaluated the electrical properties of nanowire device from I-V curves measured mainly from the bundle-like ensemble structure of ZnO, not individual ZnO NWs. Most applications require details on the electrical mobility of ZnO NWs. Recently, the electrical transport of single ZnO NWs has been studied only from several devices fabricated by electron-beam lithography. However their I-V curves categorized into three types of resistance, i.e., symmetrical, rectifying and linear shapes due to contact problems between ZnO NWs and electrodes, results in contradictory.

In this paper, we manufactured single NW device using an individual ZnO nanowire, of which the junctions were made by Pt deposition using a focused ion beam (FIB), and performed RTA processes. The single ZnO NW device consists of ZnO-Pt, ZnO-Au and Au-Pt junctions. The electrical transport of the single ZnO NW device was investigated by directly measuring the electrical resistance using nano manipulators from cross-sectioned devices. The device showed a typical Ohmic contact in I-V curves and the resistance was decrease with the RTA temperature. The CL (Cathodoluminescence) and EDS in TEM (Energy dispersive spectroscopy in transmission electron microscopy) measurements were also performed to evaluate the crystallinity (defect level) and chemical composition at the center and edge of the cross-sectioned ZnO NWs. From the results, we found that lots of defects were stored at the surface of ZnO NW and impurities at the junction were abruptly reduced. Therefore, the electrical transport of the single ZnO NW device depends strongly on the crystallinity of the ZnO NW and the C content at the Pt junction. From the electrical transport measured on the cross sectioned device, the ZnO-Au junction acted as the fastest transport path among ZnO-Pt, ZnO-Au and Au-Pt junctions in the single ZnO NW device.

We have proposed, fabricated and tested a novel structure of Field-Effect Transistor (FET) combined with carbon nanotubes (CNT) to control the process of electrolysis. Our proposed device includes a conventional n-channel MOSFET, with a selective growth of carbon nanotubes in its drain region. MOSFET is made according to standard NMOS fabrication flow chart utilizing the advantage of a self-aligned process. The CNT growth is carried out in plasma and at a high temperature environment, so a thick layer of chromium (200nm) was deposited on the whole structure as a passivating layer to overcome MOSFET degradation caused by dopant escape. Afterward we deposited and patterned a thin layer of nickel (10nm) as the catalyst of CNT growth. The CNTs are grown in a DC-PECVD system. Following this step, we etched away the chromium layer completely. After the growth, the transistors needed an annealing treatment in Argon chamber at 500°C for 5 hours to retrieve their electrical behavior. We believe this happens because the atomic hydrogen can pass through the chromium layer and passivate the impurities and annealing in Argon chamber give them enough energy to leave the silicon.

In this structure, the CNT collection is used as one-side electrode of electrolysis and the MOSFET acts as the current controller. We tested the structure to electrolyze a one molar mixture of water and salt and observed well-controlled current-voltage characteristics.

The influence of Si-doping on the growth and material characteristics of InAs nanowires deposited by metal-organic vapor phase epitaxy (MOVPE) was investigated. It was observed that above a certain partial pressure ratio, doping has an influence on the morphology. The nanowires exhibit better uniformity but lower height vs. diameter aspect ratio as the supply of the dopant increases. It was consistantly found that the specific conductance of the nanowires also increases. Moreover the electrical measurements showed a transition from semiconducting to metallic behavior in the case of highly doped nanowires.

We report an ultraviolet photoelectron spectroscopy study of the energetics at the interface between acid oxidised carbon nanotubes and the archetypical molecular N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'biphenyl-4,4'diamine(TPD). Electrical equilibrium is achieved across both interfaces within the experiment time frame due to the formation of an interfacial dipole layer which abruptly shifts the vacuum level at the interface. To the authors knowledge this is the first reported measurement of the electronic structure of a carbon nanotube / organic semiconductor interface; a system in which the magnitude of the dipole layer formed at the interface upon contact formation is proportional to the difference in work function between the substrate and organic semiconductor overlayer.

SiGe nanowires were grown by the vapor-liquid-solid method using a low pressure chemical vapor deposition reactor and different flows of the GeH4 and Si2H6 gas precursors. The morphology of the nanowires was studied by field emission scanning electron microscopy, and the length, diameter and density of nanowires were determined. Their structure and crystallinity were analyzed by transmission electron microscopy and its related techniques. Energy dispersive X-ray emission of individual nanowires as well a Raman spectroscopy were used to determine their composition and to analyze its homogeneity.

We report the fabrication of ferromagnetic NiFe nanotubes with a wall thickness of 80 nm by electrodeposition in nanoporous templates. The structure and wall thickness of the nanotubes are controlled by the thickness of the conductive layer at the back of the templates. The NiFe nanotubes have shown soft magnetic material properties with high magnetic saturation and low coercivity. The NiFe nanotube arrays are preferentially magnetized in the perpendicular direction to the nanotubes. Micromagnetic simulation results show that a curling mode is perceived with the formation of opposite magnetic vortex states on the end of the nanotube surface during the magnetization process.

In this study, we investigated the growth of silicon nanowires forced by small gallium droplet templates. Those gallium islands previously were deposited by a modified PECVD method. Two different delivery techniques of the trimethylgallium precursor (TMGa) were tested regarding their applicability. On the one hand standard liquid delivery was performed, on the other the precursor was transported by vapor draw out of the heated bubbler. The TMGa then was pulsed into the carrier gas flow. The effects on the deposited islands of both delivery methods were compared. As substrates <111> oriented p-doped silicon wafers were used. For the subsequent growth of the silicon wires similarly PECVD was used as growth method. Silane served as precursor. Argon and hydrogen were used as plasma enhanced gases. The effects of the Ga particles deposited by both process modes upon the generated wires were analyzed.

Nano- and hetero-structures of carbon nanotube (CNT) and indium tin oxide (ITO) can control significantly piezoelectric and optoelectronic properties in Microelectromechanical Systems (MEMS) as sensing and actuators under cyclic loading. Optimized preparation conditions were obtained for multi-functional purpose of the specimens by obtaining the best dispersion and turbidity in the solution. Optical transmittance and electrical properties were investigated for CNT and ITO dipping and spraying coating on boro-silicate glass and polyethylene terephthalate (PET) substrates by electrical resistance measurement under cyclic loading and wettability test. Uniform dipping coating was performed using Wilhelmy plate method due to it simple and convenience. Specimen was applied with spraying coating additionally. The change in the electrical and optical properties of coated layer is mainly dependent upon the number of dip-coating, the concentration of CNT and ITO solutions, and the surface treatment condition. Electric properties of coating layers were measured using four-point probe method, and surface resistance was calculated using a dual configuration method. Optical transmittance of CNT and ITO coated PET film was also evaluated using UV spectrum. Surface energy and their hydrophilic and hydrophobic properties of CNT and ITO coated substrates were investigated by wettability test via static and dynamic contact angle measurements. As the elapsing time of cyclic loading passed, the stability of surface resistance and thus comparative interfacial adhesion between coated layer and substrates was evaluated to compare the thermodynamic work of adhesion, Wa . As dip-coating number increased, surface resistance of CNT coating decreased, whereas the transmittance decreased step-by-step due to the thicker CNT and ITO networking layer. Nano- and hetero-structural effects of CNT and ITO solution on the optical and electrical effects have been studied continuously.

When materials are very thin in one or more dimensions, their equilibrium shapes are often curved/bent. Such shapes commonly represent a compromise between elastic strain energy and other thermodynamic forces (e.g. related to surface stresses, electrostatic interactions, or adsorption). Examples include ZnO and SnO2 nanobelts, silica/carbonate helicoids, and graphene sheets and nanoribbons. Here, we demonstrate that when the equilibrium shape of a nanomaterial is not flat/straight, important fundamental material properties may be orders of magnitude different from their bulk counterparts. We focus here primarily on the graphene edges. Graphene in three dimensions is a codimension c = 1 material; the codimension is c = D – d = 3 – 2 = 1, where D is the dimensionality of the space in which the material is embedded and d is the dimensionality of the object. By contrast, a flat graphene sheet has c = 2 – 2 = 0. We use the REBO-II interatomic potential to calculate the edge orientation dependence of the edge energy and edge stresses of graphene with c = 0 and c = 1. The edge stress for all edge orientations is compressive with c = 0. Both edge energy and stresses are in reasonable agreement with DFT calculations. The compressive edge stresses in c = 0 lead to edge buckling (out-of-the-plane of the graphene sheet) for all edge orientations (c = 1). The edge buckling in c = 1 reduces all edge energies and dramatically reduces all edge stresses to near zero (more than an order of magnitude drop). We also report the effect of codimension on the free energy and entropy of a graphene sheet and the elastic properties of ZnO nanohelices.

Tungsten oxide nanorods (TONs) with the diameters of 40 nm and the length of 130 nm have been synthesized on substrates using two step electrochemical anodizing processes. The TONs were vertically well-ordered on the substrates with the average interdistance of 100 nm. The TONs had amorphous structure and was mainly composed of W, Al, and O elements, of which the contents varied gradually along the nanorod length from the top surface to the bottom. The cyclic voltammograms (CVs) and galvanostatic charge-discharge analyses showed that TONs had the typical electrochemical pseudocapacitive features of rectangular CV hysteresis and symmetric charge-discharge behaviors, respectively. When the TONs were heat-treated at 600℃ in vacuum, they showed the maximum specific capacitance of 660 ㎌/cm2, which was higher, by an order of magnitude, than that (68 ㎌/cm2) of the TONs annealed at 300 ℃ in ambient atmosphere.

Templated growth for the fabrication of semiconductor nanostructures such as quantum dots and lattice-mismatched structures has been employed in this study. Self assembly of block copolymers (BCP) has been exploited to create a regular array of nanoscale patterns on a substrate to generate the growth template. These patterned templates were used for the selective area growth of pseudomorphic quantum dots, allowing for precise control over the dot size and spatial distribution. Strain relaxation in lattice-mismatched structures grown past the pseudomorphic limit was also studied. Analysis of the grown structures suggests that this approach using block copolymer templating followed by selective growth can be used for defect reduction in lattice-mismatched materials.