Table of contents

We report simultaneous lateral growth of a high density of highly oriented, metal-catalyzed silicon nanowires on a patterned silicon substrate and bridging of nanowires between two vertical silicon sidewalls, which can be developed into electrodes of an electronic device. After angled deposition of catalytic metal nanoparticles on one of two opposing vertical silicon surfaces, we used a metal-catalyzed chemical vapour deposition process to grow nanowires and eventually form mechanically robust 'nanobridges'. The growth and bridging of these nanowire arrays can be integrated with existing silicon processes. This method of connecting multiple nanowires between two electrodes offers the high surface-to-volume ratio needed for nanosensor applications.

The optical diffraction limit is rigidly determined as a simple equation of wavelength λ and lens numerical aperture NA (): λ/2/NA. In this paper, we report that Ag_5.8In_4.4Sb_61.0Te_28.8 and Ge₂Sb₂Te₅ chalcogenide thin films, which are typical of optical recording materials used in digital versatile discs (DVDs), enable a resolution of under λ/10 due to their ferroelectric properties. In the Ag_5.8In_4.4Sb_61.0Te_28.8 film it was found that this optical super-resolution can be observed between 350 and 400 °C, resulting in a second phase transition from a hexagonal (A7 belonging to ) to a rhombohedral structure of R32 or R3m. In Ge₂Sb₂Te₅, on the other hand, the temperature range is much wider, between 250 and 450 °C, which is also due to a second phase transition from a NaCl-type fcc to a hexagonal structure.

The nonlinear dynamics of an atomic force microcantilever (AFM) with an attached multi-walled carbon nanotube (MWCNT) tip is investigated experimentally and theoretically. We present the experimental nonlinear frequency response of a MWCNT tipped microcantilever in the tapping mode. Several unusual features in the response distinguish it from those traditionally observed for conventional tips. The MWCNT tipped AFM probe is apparently immune to conventional imaging instabilities related to the coexistence of attractive and repulsive tapping regimes. A theoretical interaction model for the system using an Euler elastica MWCNT model is developed and found to predict several unusual features of the measured nonlinear response.

This paper describes a novel technique of local surface fabrication using a scanning probe microscope with a thermally pulled micropipette probe. Submicrometre-scale fabrication of the polycarbonate surface could be realized when the polycarbonate surface and the micropipette probe filled with organic solvent (1,4-dioxane) are nearly in contact. The height and width of the fabricated dot structures could be controlled by adjusting the distance between the probe edge and the surface. It was switchable between the fabrication mode and the observation mode by shear-force control of the probe–surface distance. Dot array and line fabrication were successfully performed.

This study presents a means of calculating the cutting force during the nanomachining process using an atomic force microscope (AFM) cantilever. The determination of the cutting force in the machining system is regarded as an inverse vibration problem. The conjugate gradient method is applied to treat the inverse problem using available displacement measurements. Numerical results show that the method can accurately estimate the cutting force even for problems with error of displacement measurement. Furthermore, the initial guesses for the cutting force can be arbitrarily chosen and the computing time required for the inverse calculations takes less than one second using a Pentium III-450 MHz PC.

We investigate the structure and thermal behaviour of boron nitride (BN) nanotubes using molecular-dynamics simulations based on the Tersoff-like potential. The strain energy decreases with increasing diameter, which is proportional to the inverse square of the tube diameter on the basis of continuum elastic theory. The disintegration temperature of zigzag nanotubes is smaller than that of armchair nanotubes of nearly the same diameter and increases with increasing diameter due to the decrease in strain energy. Despite homoelemental bonds, the Stone–Wales (SW) defect is found in BN nanotubes during thermal treatment. The formation energy of the SW defect increases with increasing tube diameter. These results agree well with the trend for carbon nanotubes.

Nanoscale substrate cleanliness is an essential requirement in a variety of nanotechnology applications. The proposed particle removal technique based on pressure shock waves due to laser induced plasma is of interest in various nano/micro-manufacturing applications in which the minimum feature size is reducing rapidly. Any removal method adopted in a manufacturing process must be on the same shrinking feature reduction curve since, for device reliability, the minimum tolerable foreign particle size on a substrate depends on the minimum feature size on a nano/microsystem or device. In the current study, the transient pressure fields exerted on a surface with nanosecond pulse laser generated plasma shock waves are measured using a polyvinylidene difluoride film (PVDF)-based line transducer that was designed and tested for this particular measurement task. Using the pressure data, the corresponding diameters of latex particles that can be removed at these pressure levels are then calculated. It has been shown that latex particles as small as 60 nm in diameter can be removed from silicon surfaces using the nanosecond pulsed laser. Experimental removal data supporting these predictions are also included and discussed.

Dielectric properties of a semiconductor substrate with an imposed two-dimensional (2D) periodic grid of quantum wires or nanotubes (quantum crossbars, QCBs) are studied. It is shown that a capacitive contact between the QCB and semiconductor substrate does not destroy the Luttinger liquid character of the long-wave QCB excitations. However, the dielectric losses of a substrate surface are drastically modified due to diffraction processes on the QCB superlattice. QCB–substrate interaction results in additional Landau damping regions of the substrate plasmons. Their existence and form and the density of losses are strongly sensitive to the QCB lattice constant.

Cluster impact of single-crystal Cu induces entirely different results under different impinging velocities. We simulate the impact events by the classic molecular dynamics (MD) method. The inter-atomic interaction of Cu is modelled by both the Lennard-Jones (LJ) potential and the embedded atom method (EAM). When the cluster is impinged at a velocity of 10 km s⁻¹, a supersonic shock wave is found to propagate through the crystal, followed by stacking faults spreading into the grain. A noticeable crater is created after the impact. Under a much lower impact velocity, the plastic deformation could be recovered and the impacted surface is smoothed gradually. The cluster can not be fully planted into the substrate when the impact velocity is reduced to 2 km s⁻¹.

Activated endothelial cells (EC) are attractive prime targets for specific drug delivery using drug-carrying magnetic nanoparticles. In order to accomplish EC targeting, the interaction between magnetic particles and resting as well as activated endothelial cells must be characterized and quantified, because it will influence particle biodistribution, circulation half-time, and targeting efficacy. Here, we have quantified in vitro the interaction (adhesion/phagocytosis) between human endothelial cells and magnetite (Fe₃O₄) particles carrying different surface coatings with varying degrees of hydrophilicity and surface charge. Almost no adhesion was observed (about 1% or less) for three out of five particle types carrying plain dextran, carboxyl-substituted poly(ethylene glycol) and silica C18 coatings. In contrast, carboxyl-functionalized dextran and poly(ethylene glycol)-coated particles adhered or were phagocytosed to a considerable degree (58 and 26%, respectively). These clear and accurate results were obtained by measuring the magnetic response, i.e. magnetic susceptibility, from different fractions of the cell cultures as a means of determining the concentration of magnetic particles. Visible light and electron microscopy confirmed the magnetic quantification. To meet the need for a rapid yet sensitive instrument, we have developed a desktop magnetic susceptometer especially adapted for liquid samples or particles in a suspension. Despite its very high sensitivity, it is easy to operate and requires but a few seconds for a measurement. We also describe the construction and operation of this instrument.

The positron annihilation in nanoparticle materials has been discussed in terms of the thermal diffusion of positrons at grain surfaces and trapping at the grain interfaces and interfacial defects. The diffusion trapping model has been applied to obtain the mean lifetime of positrons as a function of grain size and temperature and the S-parameter of the annihilation radiation as a function of grain size in Ag, Nb, Zn–Al and Zn–Al–Mg nanocrystallites. The calculated mean positron lifetimes have been compared with the available experimental results. The value of has been found to decrease with an increase in the size of the grains, suggesting that the density of grain boundaries decreases gradually when the grain grows. A fast decrease in has been observed in the case of alloys but not in metals, suggesting that, in the case of alloys, grains of larger size provide trapping centres. The calculations show that the characteristics of the nanocrystalline materials undergo significant changes at lower grain size. At larger grain size the materials show behaviour similar to that in the bulk sample. The lifetime data also suggest that the grain boundaries may be composed of vacancy clusters. The diffusion coefficient has been found to be described by a relation .

We present a new technique for controlling the orientation of single-wall carbon nanotubes grown by chemical vapour deposition. The technique involves prior patterning of alumina islands on oxidized silicon substrates. Nanotubes growing on the oxide near an alumina boundary are oriented perpendicular to the boundary. Field-effect transistors were successfully fabricated from nanotubes produced using this technique. We argue that the orientation is caused by an electric field due to space charge associated with the alumina.

CdSe/PE₂ (PE means polyelectrolyte) multilayers have been successfully synthesized on the surface of SiO₂ spheres by using a layer-by-layer technique. The layer structure can be distinguished clearly and the layer thickness can be tailored easily.

The effective workfunctions of single-walled carbon nanotubes of armchair (5,5) and zigzag (9,0) with various geometries have been calculated by first-principles calculations. The results show that the capped and H-terminated zigzag (9,0) carbon nanotubes exhibit a lower workfunction value than the armchair (5,5) nanotubes with a similar diameter. The open-ended (without H termination) (5,5) nanotube, on the other hand, shows a lower workfunction than the open-ended (9,0) structure. The former exhibits a significant formation of triple bonds at its mouth part after relaxation, which reduces the surface dipole and lowers its workfunction, the latter exhibits a higher density of unsaturated dangling bonds, raising its surface dipole and giving a higher value of workfunction.

Highly ordered iron arrays of nanowires with different diameters have been prepared by the electrochemical deposition method, with the intention of studying magnetic texture in this system. Crystal texture with the [110] direction along the axis of the nanowires is demonstrated by x-ray diffraction measurements. The orientation of the magnetic moments is along the long axis of the nanowire, a result deduced from the transmission Mössbauer spectra of the as-prepared sample and the remanent states. However, as the intensity of the second and fifth lines is larger in conversion electron Mössbauer spectra than that in transmission Mössbauer spectra for the same diameter samples, the orientation of the magnetic moments appears to deviate from the axis more at the ends than that in the middle of the nanowires. On increasing the nanowire diameter, the magnetic texture becomes weaker. Large coercive force can be found for the small diameter samples when the external magnetic field is applied along the long axis of the nanowires.

By directly reducing C₂Cl₄ with Na, both multi-wall carbon nanotubes and graphite nanosheets were acquired at 140 °C in the presence of silver nanocrystals. Based on weak interaction between the p orbital of Cl in C₂Cl₄ and the empty d orbital of Ag, C₂Cl₄ can in some cases be located on the surface of silver nanocrystals. The carbon nanostructures can be directed by the morphology of silver nanocrystals. The crooked sites of silver nanocrystals lead to the formation of multi-wall carbon nanotubes while the planar sites result in the yield of graphite sheets.

Photoluminescence (PL) from SiO_x (0<x<2) thin films, prepared by evaporation of SiO powder onto the Si(100) substrate followed by thermal annealing, was investigated for various film thickness and annealing temperatures. For the film thickness ranging from 120 to 700 nm and annealing at 1100 °C for 30 min in nitrogen, the Si nanocrystals (nc-Si) embedded in SiO₂ matrix were formed due to the phase separation process, and the PL of nc-Si exhibited a continuous red-shift with increasing film thickness in an exponential decay manner. This thickness dependence was explained by a model modified from that of Zacharias and Streitenberger (2000 Phys. Rev. B 62 8391) regarding the nucleation barrier for Si clusters versus their distances away from the substrate. Further, for the film thickness of 270 nm and annealing temperature ranging from 700 to 1100 °C, it was found that a green/yellow PL structure developed at elevated annealing temperatures, which reached the maximum in intensity at 900 °C, and then dropped down for higher annealing temperatures. This PL emission was identified as due to the structural defects mainly consisting of oxygen vacancies in SiO₂ matrix.

The equilibrium water contact angles of vertically aligned nanorod Si films were measured by the sessile drop method. For as-deposited hydrophilic films, there was a contact angle transition from a rough surface to a 'hemi-wicking' porous surface at normal film thickness d = 500 nm; while for the HF treated hydrophobic films, a transition from a partially composite to a composite surface was observed at the same film thickness. The observed results can be reasonably interpreted within the framework of the classical Young theory.

We investigated atomically resolved NC-AFM images of NiO(001) surfaces obtained with ferromagnetic Fe- and Ni-coated tips and bare Si tips. The cross-sections of atomically resolved images were analysed by adding the atomic corrugation amplitude on the basis of the periodicity of the image. The topographical asymmetry is defined as an index representing the difference of the adjacent maxima. We compare the topographical asymmetry calculated from the images obtained with ferromagnetic metal- and non-coated Si tips and discuss the possible origin of the asymmetry of NC-AFM images.

A proposed method based on combining the concepts of shape functions of the finite element method (FEM) and a molecular dynamics (MD) technique was developed to evaluate the chip formation and strain and stress distribution in the cutting of single-crystal copper by a nano-scale mechanism. The displacement components for the atom in any temporary situation during the nano-scale cutting could be found.

In this paper, the atom is regarded as a node and the lattice is regarded as an element. Using the atom displacements calculated by the MD program and combining the concepts of shape functions of FEM we calculate the equivalent strain for material deformation in the atomic-scale cutting mechanism. The equivalent stress was derived from the equivalent strain from the corresponding flow stress–strain curve, whereas the flow stress–strain curve was obtained from the regression of the stress–strain curve of a nano-copper thin film tension test simulation.

In addition, the chip atoms within the diamond space were moved along the tool surface using a mathematical method. Also, this study introduced a new concept: 'a combined Morse potential function and rigid tool space restrictions criterion as the chip separation criterion' for the nano-scale cutting model.

Despite intensive research on optimizing the methods for depositing carbon encapsulated ferromagnetic nanoparticles, the effect of the carbon cages remains unclear. In the present work, the effect of the graphitic cages on the magnetization of the ferromagnetic core has been studied by comparing the magnetic properties of pure and carbon encapsulated Ni particles of the same size. The carbon encapsulated Ni particles were formed using an electric arc discharge in de-ionized water between a solid graphite cathode and an anode consisting of Ni and C in a mass ratio of Ni:C = 7:3. This method is shown to have potential for low cost production of carbon encapsulated Ni nanoparticle samples with narrow particle size distributions. X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM) analysis were used to study the crystallography, morphology, and size distribution of the encapsulated and pure Ni nanoparticle samples. The availability of encapsulated particles with various sizes allowed us to elucidate the role of carbon cages in size-dependent properties. Our data suggest that even though encapsulation is beneficial for protection against hostile chemical environments and for avoiding low proximity phenomena, it suppresses the saturation magnetization of the Ni cores.

The formation of iron particles from the supersaturated gas phase is investigated by molecular dynamics simulation. The atomic interaction is modelled with a recent parameterization of the embedded atom method which is able to describe the bcc phase of bulk iron. The influence of the state conditions such as temperature and density on the growth mechanisms of the iron particles is analysed. With the common neighbour analysis method the structural changes of the particles over the course of the growth process is traced. Furthermore, the surface fraction is investigated as an order parameter for the morphology of the particles. It appears that in the early state of the growth process the atomic structure is dominated by icosahedral structures which are, over the course of the growth process, transformed into other structures such as fcc or hcp. Iron atoms in the bcc structure were not found for small particles. The structural reorganization depends mainly on the temperature of the system and on the magnitude of the heat removal from the system. The results are in agreement with experimental and other theoretical investigations on the structure of iron nanoparticles.

Nanotubes of zinc sulfide (ZnS) have been synthesized conveniently by a simple route of solid-state reaction at room temperature and were characterized by inductively coupled plasma atomic emission spectroscopy (ICP-AES), x-ray powder diffractometry (XRD) and transmission electron microscopy (TEM). XRD showed the product obtained to be crystalline sphalerite (cubic ZnS) and TEM clearly demonstrated the nanotubes of ZnS with average diameters of about 90 nm and lengths of up to 10 µm.

Nano-TiO₂ powders were successfully prepared by laser pyrolysis of TiCl₄ (vapours). Alternatively, air and nitrous oxide were used as oxygen precursors. C₂H₄ was used as an energy transfer agent. The underlying phenomena for this photon-based molecular nanotechnology are discussed. For the present report, different titania nanosized powder batches were obtained by variation of the oxidizer nature and TiCl₄ precursor flows. X-ray diffraction, transmission electron microscopy, electron energy loss spectroscopy, x-ray dispersive energy analysis, and IR and Raman spectrometry have been used to analyse the nanostructures and morphologies of the as-synthesized powders. Medium and high resolution TEM analyses indicate mean grain sizes between 12 and 28 nm. The different characterization techniques suggest that in the obtained anatase and rutile mixture the fraction of rutile phase depends on the nature of the oxygen precursor. At low TiCl₄ flows, no chlorine contamination was detected in the reaction product. Further examination of the influence of other important system parameters will open new possibilities for titania preparation by the laser pyrolysis of TiCl₄.

We report on the synthesis of single-walled carbon nanohorns (SWNHs) by arc discharge between two graphite electrodes submerged in liquid nitrogen. The product in its powder form was found to consist of spherical aggregates with sizes in the range of 50–100 nm. The nanohorns are characterized by transmission electron microscopy (TEM), Raman and electron energy loss spectroscopies and surface area measurements. TEM observations revealed that the internal structure of the aggregates could be described as a mixture of 'dahlia-like' and 'bud-like'. A structural transition above 300 °C was inferred from the Raman data. Here we show that a simple technique that does not require relatively expensive laser and vacuum equipment provides an economical alternative for the synthesis of SWNHs.

Carbon nanotubes (CNTs) are grown by a combination of sputtering and transition metal catalysis. By focused electron-beam (FEB) irradiation, the extremely large radial dilation of the CNTs is observed. Within the deformed region (), the minimum amount of accumulated electron energy required for CNT deformation is estimated to be about 5.61 × 10¹³ eV. The successful fabrication of a CNT drive shaft component could be considered as a first attempt towards developing arduous nanoscale alteration of a target individual CNT. Our new 'dry' FEB method provides a better solution with the advantages of fast-imaging and well-positioning simultaneously.

In a DC arc-plasma method, in deionized water, used to synthesize multi-walled carbon nanotubes (MWCNTs), hard deposits collected on the surface of the cathode are the main product rich in MWCNTs and they are easier to collect than the products collected in water. The top surface of the deposit bestrewed with column-shaped clumps also gives a hint as to potential applications of the field emission. In order to increase the yield of the deposits on the cathode surface, different parameters are used to investigate their formation. An auto-formed chamber between two electrodes during the arc discharge is found to have a determining effect on the formation of deposits on the cathode surface. Deposits are examined using SEM and TEM to investigate their structure and the CNTs in them.

Using argon as the transporting gas, freestanding macroscopic ZnO strands have been synthesized by evaporating metal zinc pellets at 900 °C in a quartz tube. Scanning electron microscopy images show that the macroscopic ZnO strands are self-twined by ZnO nanowires with a diameter in the range of 20–30 nm. A ZnO strand synthesized under larger argon flux contains more oxygen vacancy, which will result in a stronger green emission at 2.43 eV. Under illumination with a power of 10 W, the photosensitivity of the ZnO strand is found to be about 800 at the bias voltage of 20 V. It is also experimentally demonstrated that the recovery time of the ZnO strand is relatively long due to the dominating surface process.

We explore Raman microprobe capabilities of visualizing single-wall carbon nanotubes (SWCNTs). Although this technique is limited to the micron scale, we demonstrate that images of individual SWCNTs, bundles, or their agglomerates can be generated by mapping Raman active elementary excitations. We measured the Raman response from carbon vibrations in SWCNTs excited by confocal scanning of a focused laser beam. Carbon vibrations reveal key characteristics of SWCNTs such as the nanotube diameter distribution (radial breathing modes (RBM), 100–300 cm⁻¹), the presence of defects and functional groups (D-mode, 1300–1350 cm⁻¹), strain and oxidation states of SWCNTs, as well as the metallic or semiconducting character of the tubes encoded in the lineshape of the G-modes at 1520–1600 cm⁻¹. In addition, SWCNTs are highly anisotropic scatterers. The Raman response from a SWCNT is maximal for incident light polarization parallel to the tube axis and vanishing for perpendicular directions. We show that the SWCNT bundle shape or direction can be determined, with some limitations, from a set of Raman images taken for two orthogonal directions of the incident light polarization.

Large-scale Y₂O₃:Eu nanotubes have been successfully fabricated by an improved sol–gel method within the nanochannels of porous anodic alumina templates. In this method, yttrium nitrate, europium nitrate and urea were used as precursors, yttrium nitrate and europium nitrate were acting as sources of europium and yttrium ions, and urea offered a basic medium through its hydrolysis. X-ray diffraction techniques, scanning electron microscopy, transmission electron microscopy and selected-area electron diffraction were used to characterize the Y₂O₃:Eu nanotubes obtained. It is found that the prepared Y₂O₃:Eu nanotubes can be indexed as a polycrystalline cubic structure and their outer diameters are about 50–80 nm, with the thickness of the tube wall estimated to be around 5 nm. The emission peaks of the as-prepared Y₂O₃:Eu nanotubes are broader than those of bulk Y₂O₃:Eu because of the disordering of the crystal phase possibly induced by the increase of the surface/volume ratio in the nanotubes.

Nanostructured ZnSe (Q-ZnSe) films synthesized by a wet chemical route have been studied. The evolution of particle size dependent strain, morphology and luminescence properties have been investigated, using x-ray diffraction, atomic force microscopy, transmission electron microscopy and optical absorption and luminescence spectroscopy. It is shown that the degree of structural orientation, self-organization and the nature of strain are dependent on particle size. Self-organized Q-ZnSe films with narrow particle size distribution have been successfully synthesized. Systematic particle size dependent blue shifts in the optical absorption edge and PL maxima have also been reported.

Single-crystalline wurtzite ZnS nanobelts were synthesized by the VPT process for the first time in the presence of Au catalyst on the Si substrates. Each ZnS nanobelt is fairly straight. The ZnS nanobelts are 50–100 µm in length, 150–600 nm in width and 3–10 in ratio of the width to the thickness. The crystalline directions along the length and the width dimensions of the ZnS nanobelts are perpendicular to and make angles within the range 0°–15° to and [0001] crystalline directions, respectively. Strong near-band-edge emission at 344 nm was detected.

The incorporation of 23 nm titanium dioxide nanoparticles into an epoxy matrix to form a nanocomposite structure is described. It is shown that the use of nanometric particles results in a substantial change in the behaviour of the composite, which can be traced to the mitigation of internal charge when a comparison is made with conventional TiO₂ fillers. A variety of diagnostic techniques (including dielectric spectroscopy, electroluminescence, thermally stimulated current and photoluminescence) have been used to augment pulsed electro-acoustic space charge measurement to provide a basis for understanding the underlying physics of the phenomenon. It would appear that, when the size of the inclusions becomes small enough, they act cooperatively with the host structure and cease to exhibit interfacial properties, leading to Maxwell–Wagner polarization. It is postulated that the particles are surrounded by high charge concentrations in the Gouy–Chapman–Stern layer. Since nanoparticles have very high specific areas, these regions allow limited charge percolation through nano-filled dielectrics.

The practical consequences of this have also been explored in terms of the electric strength exhibited. It would appear that there was a window in which real advantages accrue from the nano-formulated material. An optimum loading of about 10% (by weight) is indicated.

Large-scale single-crystalline In₂O₃ nanowires were successfully synthesized by a simple physical evaporation method at 950 °C. The as-synthesized products, characterized by XRD, SEM and TEM, are pure, structurally uniform and single crystalline with typical diameters of 10–100 nm and lengths of up to a few hundreds of micrometres. Two strong and wide violet emission bands centred at 388 and 401 nm are observed in the room-temperature photoluminescence measurements and their mechanism is discussed.

A wide range of nanomaterials has been grown by thermal treatment of patterned condensed-phase precursors. We present a systematic study of the thermolysis of fullerene, amorphous carbon and transition metal thin films, trying to bridge previously reported results in the high temperature regime (>900 °C) and reporting novel structures for low temperature (<550 °C) processing. The synthesis of crystals of single-walled carbon nanotubes from high temperature annealing of patterned, multilayered fullerene and nickel precursor films, could not be reproduced. A thicker fullerene layer in the presence of nickel was, however, transformed into a web-like carbon network. Low temperature processing of similar precursor patterns on sulfur-containing molybdenum grids resulted in the self-assembly of nickel sulfide nanowires and filled MoS₂ nanotubes. Cobalt was found to form cobalt sulfide structures. The strongly oxidizing behaviour of iron resulted in an abundance of needle-like molybdenum oxide crystals. None of the structural formations could be seen for amorphous carbon as a substitutional thin film precursor. Based on the ease of changing precursor materials, this simple, scaleable method addresses many nanomaterials, giving new insight into growth mechanisms as well as offering synthesis control for future applications.

Two tunnel-coupled few-electron quantum dots were fabricated in a GaAs/AlGaAs quantum well. The absolute number of electrons in each dot could be determined from finite-bias Coulomb blockade measurements and gate voltage scans of the dots, and allows the number of electrons to be controlled down to zero. The Zeeman energy of several electronic states in one of the dots was measured with an in-plane magnetic field, and the g-factor of the states was found to be no different from that of electrons in bulk GaAs. Tunnel coupling between dots is demonstrated, and the tunnelling strength was estimated from the peak splitting of the Coulomb blockade peaks of the double dot.

We investigated fullerene and metallofullerene nano ball bearings using classical molecular dynamics and steepest descent methods based on both the Tersoff–Brenner and the Lennard-Jones 12–6 potentials. Under hydrostatic pressures, the bulk modulus and the ultimate pressure of K @C₆₀ were higher than those of C₆₀. While C₆₀ rolling dynamics were the same as K @C₆₀ rolling dynamics, the sustaining pressure of K @C₆₀ intercalated between layers was higher than that of C₆₀ intercalated between layers. In molecular dynamics simulations of C₆₀ and K @C₆₀ rolling motions, periodic variations of the frictional forces were found and the mean dynamical frictional forces were almost zero. We were able to conclude that K @C₆₀ was more effective than C₆₀ for the application of nano ball bearings.

Flower-like ZnO nanostructures, which consisted of sword-like ZnO nanorods, have been prepared by an organic-free hydrothermal process. The XRD pattern indicated that the flower-like ZnO nanostructures were hexagonal. The SAED and HRTEM experiments implied that the sword-like ZnO nanorods were single crystal in nature and preferentially grew up along the [001] direction. The effects of temperature, pH value and mineralizer on the morphology have been also investigated. It is considered that pH value is the main factor to influence the morphology because of its effect on the initial nuclei and growth environment of ZnO. Finally, the mechanism for organic-free hydrothermal synthesis of the flower-like ZnO nanostructure is discussed.

The phase mode of electrostatic force microscopy (EFM-phase) is a scanning probe microscopy (SPM) technique used to measure electrostatic force gradient. EFM-phase has a higher resolution than scanning Kelvin probe microscopy (SKPM or SKM), but unlike SKPM it does not yield a direct measurement of local potential. Analytical calculations of tip–surface capacitances and their gradients are presented, and the origin of the measurement resolution in EFM-phase and SKPM is explained based on the calculation results. We show that EFM-phase data fit the analytical calculation well, and can be interpreted using a simple analytic model, which allows phase shift to be related to the local surface potential. The analytic formula is easy to calibrate and can be used to convert the EFM-phase data to potential data. This procedure is demonstrated on a poly-(3-hexylthiophene-2,5-diyl) (P3HT) thin film, contacted with Au electrodes, and the potential distributions of the Au/P3HT/Au structure under various biases are presented.

We report on the properties of a new air-stable nanowire material with the chemical formula Mo₆S₃I₆. The distinguishing features of the material are rapid one-step synthesis, easy isolation and controllable dispersion into small-diameter wire bundles. Elemental analysis, x-ray diffraction, thermogravimetry, differential thermal analysis, Raman scattering and electron microscopy were used to characterize the material.

We report on the production of large-area 2D photonic crystals from high-index material with laser interference lithography (LIL). A new image reversal photoresist is used in combination with an anti-reflection coating to suppress undesired reflections. The photonic crystals possess a cubic pattern of air holes in a 500 nm silicon layer and cover an area of 1 cm².

We describe the use of Er(tBuNC(CH₃)NtBu)₃ as a dopant source in the preparation of silicon nanocrystals, particularly as regards their observed structure, composition, and photophysical properties. These nanocrystals were prepared by the co-pyrolysis of Er(tBuNC(CH₃)NtBu)₃ and disilane in a dilute helium stream at 1000 °C. Characterization methods include high resolution electron microscopy, selected area electron diffraction, energy dispersive x-ray measurements, extended x-ray absorption spectroscopy, and photoluminescence spectroscopy. In conditions identical to those used previously for β-diketonate precursors, nanocrystals doped using this amidinate source are larger in size, of a narrower size distribution, and contain more erbium in the nanocrystal on average. Steady state photoluminescence measurements as a function of excitation wavelength confirm that the characteristic 1540 nm emission detected in these nanocrystals emit by a silicon exciton-mediated pathway. These results are a clear example of precursor dopant chemistry exerting a significant effect on resultant nanoparticle properties.

Nanoscale particles of Ni₃Al-type intermetallic phase have been produced by extracting precipitates from Ni-base superalloys. The process is flexible and can be easily manipulated to tailor particle size and composition. Further, it can be readily adopted to produce nanoparticles of many other intermetallic phases with diverse compositions. The Ni₃Al-type nanopowder ( nm particle size) was characterized by x-ray diffraction and electron microscopy and compared with a micropowder ( nm particle size). The nanopowder shows enhanced specific magnetization and a slight increase in Curie temperature relative to the micropowder. This change is possibly due to small changes in composition rather than to the reduction in particle size.

Raman spectroscopy was used to investigate excimer laser annealing and thickness determination of amorphous silicon (a-Si) layers which are less than 20 nm thick. The a-Si layers were produced on silicon (Si) substrates using Si⁺ ion implantation with an energy of 10 keV and a dose of 1 × 10¹⁵ cm⁻². Excimer laser annealing was applied to re-crystallize the a-Si layers. The dependence of re-crystallization on laser fluence was investigated using Raman spectroscopy. A threshold laser fluence of 0.4 J cm⁻² was required to re-crystallize the a-Si layers. In Raman spectroscopy, the Raman intensity shows a periodical variation with a period of 90° as a function of the angle between the Si orientation and the laser polarization. Based on this phenomenon, a method to determine nanoscale a-Si film thickness was proposed in two ways. One way was carried out without sample rotation to determine the a-Si thickness provided that the reference c-Si and a-Si/c-Si samples are in the same crystal orientation. The other way was carried out with sample rotation to determine the a-Si thickness without knowing the crystal orientation beforehand.

Carbon nanotubes (CNTs) and zirconium carbide (ZrC) composite films were directly grown on Zr–Fe coated glass by chemical vapour deposition. The Zr–Fe film not only acts as a catalyst to facilitate the nanotube growth, but also offers a template to form the ZrC phase. The Zr content in the Zr–Fe bimetallic catalyst can influence the carbon production rate so as to grow long CNTs, yielding a high aspect ratio. In comparison with CNTs grown on a pure Fe catalyst, the composite film promotes the growth of sparse and long nanotubes. Field emission measurements revealed that the composite film exhibits a relatively low turn-on field of 3.2 V µm⁻¹.

Recent experiments have shown that multi-phase epilayers may self-organize into ordered nanoscale patterns on a solid substrate. In this paper, we present a phase field model for the self-assembly of three-phase epilayers. Nanoscale patterns are developed by two competing actions: coarsening due to phase boundary energy and refining due to substrate-mediated elastic interaction. The continuum phase field approach leads to a set of nonlinear diffusion equations, which couples the two concentration fields in the epilayer and the stress field in the substrate. Numerical simulations reveal remarkably rich dynamics in the self-assembly of multi-phase epilayers. An epilayer may evolve into various patterns, suggesting a significant degree of experimental control in growing nanoscale structures.

In this paper we describe the technological and fabrication methods necessary to incorporate both photonic and electronic-band engineering in order to create novel surface-emitting quantum cascade microcavity laser sources. This technology offers the promise of several innovative applications such as the miniaturization of QC lasers, and multi-wavelength two-dimensional laser arrays for spectroscopy, gas-sensing and imaging. This approach is not limited to light-emitting devices, and may be efficiently applied to the development of mid- and far-infrared normal-incidence detectors.

The thermal behaviour of octadecylphosphonic acid (OPA) self-assembled bilayers (SABs) was investigated by atomic force microscopy employing ex situ and in situ annealing treatments. An interesting stacking effect was observed for OPA SABs deposited on different substrates within the temperature range 80–110 °C, which was associated with the formation of hydrogen bonds between OPA headgroups at the surface of bilayers. Infrared spectroscopy was used to confirm the formation of H-bonds during the stacking process.

We report a technique to grow a single tungsten nanowire at a predetermined location by using field emission in a low-pressure tungsten carbonyl atmosphere. A sharp tip is first made to contact the intended location of growth. Electrical current is then passed through the contact. When the contact is broken, the resulting localized plasma discharge at the point of breakage causes a nanowire to initiate. Continued growth at low currents results in a single nanowire a few nanometres in diameter and up to tens of micrometres in length. The nanowire is overcoated by a thin carbon layer which protects the metal core from oxidation and corrosion. Electrical measurements of nanowires grown between two pads show resistivity one to two orders of magnitude higher than that of bulk tungsten. The technique can be applied to the interconnection of nanostructures to electrodes on a die.

Molecular dynamics (MD) simulations have been carried out in order to investigate morphological changes in three different crystallographically oriented silicon surfaces during nanoindentation. Transformations to fivefold and sixfold coordinated structures are observed during the contact loading. However, the atoms are arranged in a complex mix of different local structures rather than forming a new crystalline phase. This region forms a thin layer of around 15 Å under the contact area. The thermal vibration of the atoms is found to have an important role in the recovery of the damage region during tip retraction.

Three-dimensional (3D) Ta₂O₅/SiO₂ photonic crystals in the visible-violet spectral region are fabricated by an auto-cloning technique on patterned substrates with triangular lattice configurations and their in-plane (the stack XY plane) optical properties are studied. Reflection measurements by normal incidence of light on to the cleaved facet of the photonic crystal reveal maximum reflections at certain photon energies. Comparison with calculated band structure demonstrates that the reflection peaks are either due to the photonic bandgap (PBG) within which the light propagation is forbidden, or due to heavy photons associated with flat bands. A two-step deposition method is adopted to insert luminescent rhodamine 590 into the photonic crystal and the emission property is strongly modified by the photonic crystal. Possible applications of such 3D photonic crystals in optical components are discussed.

The method of spectroscopic ellipsometry has been applied to study in situ the adsorption of bovine serum albumin (BSA). The porosity and amount of adsorbed BSA were determined by fitting the ellipsometric data to the Bruggeman effective medium approximation model. The presence of intermediate adsorbed layers of polyelectrolytes was found to increase protein adsorption.

We attempted molecular dynamics (MD) simulation of non-contact atomic force microscopy (nc-AFM) of a self-assembled monolayer (SAM) on Au(111) by modifying a previously developed MD simulation method. In the previous simulation, the interaction between a single gold atom tip and a SAM sample consisting of the united atoms (CH₃) with a mass (m₀) and a continuum gold substrate was treated explicitly in terms of microscopic potentials. On the other hand, the probe tip with an artificial reduced mass (m_sl) was bound to a cantilever spring in order to describe its macroscopic nc-AFM behaviour. In the present study, we treated explicitly the interaction between a gold probe tip (the radius = R) having a single gold atom at the apex and the same SAM on gold. By using this new MD method, we succeeded in interpreting our recent experimental nc-AFM observation. Namely, the local atom–atom interactions in terms of Lennard-Jones potentials together with the long-range sphere–substrate interaction are responsible for inversion and molecular-dependent imaging of van der Waals (i.e. chemically inert) molecules bound on gold substrates.