Table of contents

We summarize our correlated scanning tunnelling microscopy and optical spectroscopy investigations of the electronic level structure and single-electron charging effects in CdSe quantum rods. Both optical and tunnelling spectra show that the level structure depends primarily on rod diameter and not on length. With increasing diameter, the bandgap and the excited state level spacings shift to the red. The level structure is assigned using a multi-band effective-mass model. The tunnelling spectra also exhibit, depending on the tunnel-junction parameters, single-electron charging effects that yield information on the degeneracy of the electronic states.

The influence of wetting-layer states on quantum-dot states and vice versa is analysed numerically for electrons in the conduction band in the general case with arbitrary kinetic energy in the plane of the quantum-well wetting layer. Since the analysed quantum dot is embedded in a barrier material with different properties, the effective mass approximation methodology leads to a Schrödinger model with discontinuous coefficients. This complicates the analysis and, in addition, requires a special attention to the formulation of boundary conditions for the entire structure, consisting of the quantum dot with wetting layer embedded in a barrier material. In the present paper, the complete model is formulated and solved numerically via a variational approach based on finite element approximations and Arnoldi iterations. By analysing different geometrical configurations, we demonstrate that the ground eigenstate of the entire structure can be considerably affected by the presence of the wetting layer. The dependency demonstrated between eigenstates of the 'pure' quantum dots and the quantum-well wetting layers indicates that a conventional analysis of quantum-dot structures without accounting for wetting layers may not be sufficient for an adequate characterization of quantum dots as active regions in future electronic and optical devices.

The growth of carbon nanofibres (CNF) by plasma enhanced chemical vapour deposition (PECVD) and the integration of CNFs into devices are studied using high throughput methodology. A growth compatibility chip containing candidate metal contact underlayers and transition metal catalyst layers are used to explore growth activity from various pairings of these two layers. In addition, catalyst density microarray chips (CDMCs) where each chip consists of catalyst patterns with various feature sizes and densities were used to investigate CNF growth and integration. The CDMCs were used to efficiently explore CNF growth conditions as well as subsequent downstream integration and testing for applications in ultrasensitive biosensing and field emission. The methodology described here is widely applicable as a general approach for optimizing the bottom-up growth and integration of nanostructures.

Effective surface passivation of lead sulfide (PbS) nanocrystals (NCs) in an aqueous colloidal solution has been achieved following treatment with CdS precursors. The resultant photoluminescent emission displays two distinct components, one originating from the absorption band edge and the other from above the absorption band edge. We show that both of these components are strongly polarized but display distinctly different behaviours. The polarization arising from the band edge shows little dependence on the excitation energy while the polarization of the above-band-edge component is strongly dependent on the excitation energy. In addition, time-resolved polarization spectroscopy reveals that the above-band-edge polarization is restricted to the first couple of nanoseconds, while the band edge polarization is nearly constant over hundreds of nanoseconds. We recognize an incompatibility between the two different polarization behaviours, which enables us to identify two distinct types of surface-passivated PbS NC.

Pb_1−xFe_xS nanoparticle films were grown on silicon substrates under zero, positive and negative biasing by the chemical bath deposition technique. The grain size for films with a fixed x was observed to increase with positive biasing and decrease with negative biasing of the substrates. Distortion of the lattice is observed to increase and the average grain size decreases as the substrate bias is changed from positive through zero to negative values. The DC conductivity of the films decreases with decrease in grain size due to enhanced surface scattering. The nanoparticle films are semiconducting and show a predominance of variable range hopping of the carriers among localized states.

Highly ordered vanadium–iron cyanide molecular magnet nanowire arrays have been prepared for the first time using an electrodepositing technology with two-step anodized anodic aluminium oxide films. Selectable diameters and lengths of the nanowires can be obtained by controlling the diameters of the nanopores in the anodic aluminium oxide films and the electrodepositing time, respectively. X-ray diffraction and transmission electron microscopy measurement results show that the vanadium–iron cyanide nanowires are straight, continuous, and highly crystalline with a face-centred cubic cubic structure of a = 10.14 Å. The x-ray photoelectron system, Mössbauer spectrum and infrared spectrum measurement results indicate that the oxidation state of the metal ions in the vanadium–iron nanowires can be expressed as V⁴⁺–CN–Fe²⁺. The hysteresis loop of the vanadium–iron cyanide nanowires at 1.9 K indicates that there are magnetic exchange interactions between vanadium and iron ions in the nanowires.

We have synthesized Pb(Zr_0.52Ti_0.48)O₃ fibres with diameters ranging from 500 nm to several microns using electrospinning and metallo-organic decomposition techniques (Wang et al 2002 Mater. Res. Soc. Symp. Proc.702 359). By a refinement of our electrospinning technique, i.e. by increasing the viscosity of the precursor solution, and by adding a filter to the tip of the syringe, the diameter of the synthesized PZT fibres has been reduced to the neighbourhood of 100 nm. The complex thermal decomposition was characterized using Fourier-transform infrared (FTIR) spectroscopy and x-ray diffraction (XRD). It was found that alcohol evaporated during electrospinning and that most of the organic groups had pyrolysed before the intermediate pyrochlore phase was formed. There is a good correspondence between XRD and FTIR spectra. We also verify that a thin film of platinum coated on the silicon substrate catalyses the phase transformation of the pyrochlore into the perovskite phase.

Controlling the size, shape and structure of nanocrystals is technologically important because of the strong effect of size and shape on optical, electrical, and catalytic properties. Monodispersed nanocrystals of copper oxide were prepared by the precipitation–pyrolysis method. By controlling the starting materials, reactive concentration and annealing temperature, we can obtain spherical monodispersed CuO nanocrystals of different sizes or rodlike CuO nanocrystals. The particle sizes of CuO monodispersed nanocrystals can be tuned in the range between and 30 nm. The products have been characterized by x-ray diffraction, transmission electron microscopy, high-resolution transmission electron microscopy and the UV–visible absorption spectrum. The absorption spectra of CuO nanocrystals show clear evidence of the quantum size effect. The possible formation mechanism of monodispersed CuO nanocrystals is discussed.

Carbon-coated Co and Ni nanocrystallites were effectively synthesized by an AC arc discharge method under an N₂ atmosphere with yields over 80%. The metal content of as-made Co and Ni samples was determined by a thermogravimetric method and it was found that the metal content increased by raising the metal loading ratio in the electrodes. The morphology, structure and magnetic properties of the Co and Ni samples were investigated by transmission electron microscope, x-ray powder diffractometer and vibrating sample magnetometer, respectively. In addition to the carbon-coated Co and Ni nanocrystallites, a small number of carbon nanotubes were also observed in the as-made Co and Ni samples. The values of saturation magnetization (M_s) for the sample containing 26.2 wt% of Co and the sample containing 37.6 wt% of Ni prepared under N₂ gas were 21.7 and 14.0 emu g⁻¹, respectively. However, M_s for 28.8 wt% of Co and 40.9 wt% of Ni prepared under He gas were 16.8 and 9.0 emu g⁻¹, respectively. This suggested that the carbon-coated Co and Ni nanocrystallites prepared under N₂ gas had larger values of M_s than that of those prepared under He gas.

For the continuous monitoring, diagnosis, and treatment of neural tissue, implantable probes are required. However, sometimes such neural probes (usually composed of silicon) become encapsulated with non-conductive, undesirable glial scar tissue. Similarly for orthopaedic implants, biomaterials (usually titanium and/or titanium alloys) often become encapsulated with undesirable soft fibrous, not hard bony, tissue. Although possessing intriguing electrical and mechanical properties for neural and orthopaedic applications, carbon nanofibres/nanotubes have not been widely considered for these applications to date. The present work developed a carbon nanofibre reinforced polycarbonate urethane (PU) composite in an attempt to determine the possibility of using carbon nanofibres (CNs) as either neural or orthopaedic prosthetic devices. Electrical and mechanical characterization studies determined that such composites have properties suitable for neural and orthopaedic applications. More importantly, cell adhesion experiments revealed for the first time the promise these materials have to increase neural (nerve cell) and osteoblast (bone-forming cell) functions. In contrast, functions of cells that contribute to glial scar-tissue formation for neural prostheses (astrocytes) and fibrous-tissue encapsulation events for bone implants (fibroblasts) decreased on PU composites containing increasing amounts of CNs. In this manner, this study provided the first evidence of the future that CN formulations may have towards interacting with neural and bone cells which is important for the design of successful neural probes and orthopaedic implants, respectively.

A novel microemulsion process was introduced for the large-scale synthesis of uniform Ag₄SiW₁₂O₄₀ nanowires with an average diameter of about 8 nm and length of up to 10 µm. The ageing time of the reaction mixture played an important role in controlling the morphology of the products, and the interaction between ethanol and AOT (sodium bis-(2-ethyexylsulfosuccinate)) can be used to illustrate the formation of the nanowires. The products were characterized by IR, TEM and XRD techniques.

The paper describes the self-assembly synthesis of Co–P alloy nanowire arrays in an anodic alumina membrane (AAM) by electroless deposition and presents their corresponding magnetic properties. The images of Co–P alloy nanowire arrays and single nanowires are obtained by scanning electron microscopy and transmission electron microscopy, respectively. Selected area electron diffraction, x-ray diffraction and energy dispersive spectra are employed to study the morphology and chemical composition of the nanowires. The results show that Co–P alloy nanowire arrays are amorphous. The magnetic properties of Co–P alloy nanowire arrays is characterized using a vibrating sample magnetometer. The hysteresis loops indicate that the easily magnetized direction of Co–P nanowire arrays is parallel to the nanowire arrays and has obvious magnetic anisotropy as a result of the shape anisotropies. Electroless deposition can be extended to many other materials and opens up significant opportunities in nanoscalar fabrication magnetic materials for ultra-high-density magnetic recoding media. Compared with the electrodeposition method, electroless deposition need not supply power or sprinkle Au on one side of the AAM before deposition and some defects of electrodeposition can be overcome.

A 340-element array of microhotplates was used to characterize the chemical vapour deposition growth of carbon nanotubes and nanofibres under a variety of process conditions. One dimension of the 17 by 20 element array was used to vary the thickness of a Ni catalyst layer. The second dimension was used for temperature control. Growth took place in an ambient temperature gas flow system, with processes only occurring on activated heaters. This allowed different process sequences to be defined on different columns of the array. Four parameters were varied: pre-anneal temperature of the catalyst, growth temperature of the carbon nanostructures, growth pressure, and growth time. Scanning electron microscope images of each array element revealed trends in microstructure as these parameters, together with the catalyst thickness, were varied.

Conducting polypyrrole nanotubes are synthesized by an oxidation polymerization technique using an Anodisc alumina membrane as a template. The morphology is varied from solid rod-like structures to hollow tubes by changing the concentration of the ammonium persulphate (used as the oxidant) solution. The current distribution over the selected area of the membrane and the current–voltage (I–V) characteristics of a single nanotube have been investigated by atomic force microscopy. From the current distribution, the lowest wall thickness has been estimated to be and from the I–V characteristics it is seen that the intrinsic conductivity of the tube changes with the wall thickness. The conductivity for tubes with a wall thickness of has been calculated as .

Monodisperse cobalt nanoparticles (NPs) are synthesized via a high-temperature thermal decomposition method in the presence of oleic acid and triphenylphosphine. The as-synthesized NPs are stable against further deep oxidation when they are kept in heptane (C₇H₁₆). Time-dependent x-ray photoelectron spectroscopy studies indicate that the oxidation of the as-synthesized cobalt NPs by air is slow and the valence change of cobalt from the Co NP sample kept in heptane under air is not observed for 120 days. The cobalt NPs have β-manganese type structure (also called ε-cobalt). Annealing the NPs at 500 °C under Ar (95%)+H₂ (5%) converts these particles from ε-Co to fcc-Co. Two-dimensional (2D) and three-dimensional (3D) self-assembled superlattices of passivated cobalt NPs are formed by slow evaporation of the carrier solvent.

Nanocrystalline yttrium oxide doped with the lanthanide ions Sm³⁺, Dy³⁺ or Tm³⁺ with a particle diameter of approximately 10 nm was prepared by propellant synthesis. The Y₂O₃:Sm³⁺ nanocrystals showed a visually dominant red emission from the transition and a strong concentration dependence of both the emission spectra and decay was observed. The decay time of the ⁴G_5/2 excited state in the 1 mol% nanocrystalline Y₂O₃:Sm³⁺ sample was determined to be longer than in the identically doped bulk (microcrystalline) sample. We have shown that the lifetime of this state in the nanocrystalline material is strongly dependent on the index of refraction of the medium surrounding the nanoparticles and a 0.75 filling factor was obtained. Yellow emission was observed from the Y₂O₃:Dy³⁺ nanocrystals from the transition. The decay curves of the ⁴F_9/2 state deviated from exponentiality and were fitted with the Inokuti–Hirayama model in order to probe the energy transfer processes. The model revealed that a dipole–dipole mechanism was responsible for the interactions and a critical transfer distance (R₀) of 6.05 Å was obtained. Tm³⁺ doped Y₂O₃ nanocrystals showed predominantly blue emission from the and transitions. Red-to-blue up-conversion was detected following excitation with 656 nm into the ³F₂ state which occurred via a two-photon ESA/ETU process.

Fractal Pd islands have been used to demonstrate that a metal patterned highly oriented pyrolytic graphite (HOPG) is a suitable template for direct molding of cavities and channels on elastomeric polymeric materials. Due to the low reactivity of the surface the method requires neither substrate surface modification nor subsequent steps so that it is very simple and inexpensive. Features larger than 20 nm in size can be easily transferred from the template to the mold. Damage was observed neither in the patterned polymeric material nor in the HOPG template after release of the polymer film.

We present a 'flip chip' technique for testing electronic self-assembled monolayers (SAMs). Metal–SAM–metal junctions with contact areas of approximately (25 nm)² and smaller have been created and tested. While the approach is similar in spirit to conductive atomic force microscope measurements, it requires only straightforward optical lithography to create the test chips and a simple gravitational-force flexure to close the junction with sub-angstrom scale precision. The junction is formed in a vertical manner, in which the SAM is grown on one or both metal electrodes, and the circuit is closed via the pressure-induced flexing of one chip into another. This method of creating a junction is rapid and facilitates multiple measurements per chip set. We have investigated the electrical transport characteristics of a variety of SAMs using this technique, including aliphatic alkanethiols and aromatic dithiols. Results are consistent with junction contact areas , and elucidate information regarding the role of pressure and defects on SAM transport.

An agarose gelatin having nanoscale transport properties similar to those of in vivo mammalian brain was employed as a surrogate for living brain tissue in the evaluation of infusion therapy protocols and neurocatheters to be used in the treatment of brain tumours. The catheters under study were a polyimide tube of 950 µm outer diameter (OD) and 750 µm inner diameter (ID), and a silicone tube of 2.5 mm OD and 1.25 mm ID. From the pressure profiles that were measured during infusions of a solution of Bromphenol Blue dye into this gel, we infer that forces on the order of 0.1 fN were driving the solute molecules through the  nm intramatrix voids in the gel at rates of , which is within a factor of 5 of the value derived from the time rate of change of the volume of distribution of the infusate. In some of the infusions, a column of trapped air was left purposely in the catheter prior to delivery of dye into the gel in order to mimic the clinical situation where the neurosurgeon must keep the catheter unprimed because of the need to use a stylet to guide it into the brain. (In those cases, the catheter is attached to the infusion pump only following withdrawal of the stylet, and there is thus a column of air inside the catheter.) In our series of such 'unprimed infusions', an oscillatory behaviour in the pressure profiles was observed, with a centre frequency of  mHz. Surface tension effects in the resulting air bubbles within the gel likely limited to <3 nm the range of pore sizes into which flows could be coupled in that case. Circumstances associated with backflow of the dye along the catheter insertion path are also discussed.

Nanocomposite materials consisting of monodisperse SiO₂ particles embedded in a polymerized resin matrix were produced by the adhesion of silica globules on the surface of a chemically modified phenolic-formaldehyde resin (MPFR) substrate that incorporates carboxylic groups in its molecules. Two routes were followed to obtain SiO₂ nanoparticles–MPFR materials. The first procedure consisted of the growth of an SiO₂ phase concurrently with the presence of MPFR molecules. The second procedure involved the preparation of a monodisperse SiO₂ sol that was subsequently mixed with an MPFR solution. The thermal curing of the MPFR resin phase at 80 °C brought about thin SiO₂–MPFR flakes from samples obtained from procedure 1 whilst monolithic pieces arose from samples from procedure 2. During the curing process, silanol surface groups of the silica globules reacted with carboxylic groups of the MPFR molecules to create a reinforced SiO₂–MPFR substance that displayed ester bonds across the interface. Thermal treatments of specimens prepared by procedure 2 were performed at 150, 250, 400, 600 and 800 °C to monitor the integrity of the resultant hybrid substrates. To assess the characteristics of SiO₂–MPFR materials, some of the main chemical, structural and textural characteristics of several specimens have been determined via FTIR, SEM and N₂ adsorption studies.

This paper presents both experimental and theoretical studies on the atomic structure changes of monocrystalline silicon brought about by surface nano-modification. The experiment revealed amorphous transformations with boundaries featuring faceting along {111} planes near the sample surface, which were altered to a random nature at the bottom of the transformation zone. The deformation outside the zone was minor near the surface, but advanced to heavy bending, extensive dislocations and plane shifting in the depth of the samples. Theoretical analysis closely reproduced this deformation, highlighting some scaling effects.

An advanced controller consisting of a feedback and feedforward part is presented to improve the performance of an atomic force microscope (AFM) enabling topography measurements at higher scan rates with a reduced measurement error. The tip–sample interaction force is held constant by an -controller while the scanner is simultaneously tracked to the topography of the last recorded scan line by a model-based feedforward controller. The designed controller is implemented on a commercial AFM system to compare the performance to a standard proportional integral controlled AFM. The new controller reduces the measurement error and enables imaging at higher speeds and at smaller tip–sample interaction forces.

Caesium structures encapsulated in CNTs were investigated using a structural optimization process applied to a steepest descent method. As the radius of the CNTs increased, the optimal structures were found in various phases from an atomic strand to multi-shell packs composed of coaxial cylindrical shells, and both helical and layered structures were found. The numbers of helical atom rows composed of coaxial tubes and the orthogonal vectors of the circular rolling of a triangular network can explain the structures of ultra-thin caesium nanowires encapsulated in CNTs.

The cytoskeleton is a dynamic structural framework fundamental to cell shape and to intracellular structural elements within each cell and their functioning. Using techniques and concepts from the fields of physics and cell biology, our study attempted to find out whether and how the intracellular structures change under applied stress acting on the cytoskeletal fibres within living cells. Here we report that in vitro atomic force microscopy, using the force curve technique during the tapping mode, was used as a tool to apply a nanonewton force. This was achieved by tapping a cytoskeletal fibre bundle within living rat cerebral microvessel endothelial cells on a nanometre scale. The results show that tapping a single point on a certain cytoskeletal fibre bundle artificially removes certain structural elements and to a certain degree results in the rebuilding of the cytoskeletal networks. This suggests that certain stress-sensitivity points exist on the cytoskeletal fibre network and elaborate change in cell structure and shape could be achieved through the application of stress from outside cells.

Vacancy induced p–n homojunctions have been successfully grown in situ from an aqueous solution bath in Pb_1−xFe_xS (x = 0.25 and 0.50) semiconductor nanoparticle films. An abrupt change of DC bias to the substrate during growth has been used as a technique to fabricate p–n junctions. (I–V) and (C–V) measurements confirm the formation of homojunctions in the nanoparticle thin films.

We report the first ever demonstration of using silane directly in the gas phase and molten gallium in a microwave plasma for bulk nucleation and growth of single-crystal quality silicon nanowires. Multiple nanowires nucleated and grew from micron- to millimetre-sized gallium droplets. The resulting nanowires were tens to hundreds of nanometres in diameter and were tens to hundreds of microns long. Transmission electron microscopy results confirmed the nanowires to be single crystalline, devoid of structural defects, and grown along the direction. The as-synthesized silicon nanowires were sheathed with an ultrathin (<1 nm) non-uniform native oxide amorphous layer that could be directly used in the assembly of electronic and optoelectronic devices.

We have investigated a novel soft-imprint technique for the fabrication of submicron scale polymer structures that can be simply performed at room temperature by polymerization with an elastomeric polydimethylsiloxane (PDMS) mould. The proposed technique is a simple, cheap and reproducible method for the patterning of large areas, and that allows the transfer of polymer patterns at the submicron scale without high pressures. The PDMS mould is placed on a fluid mixture of prepolymer and monomer after a brief UV exposure, full polymerization follows, and then the mould is removed. SEM and AFM observations confirm that the submicron scale polymer structures are produced without any defect or distortion and with good pattern fidelity over a large area.

Nanojunctions made from one-dimensional nanostructures could provide fascinating opportunities to reveal new mesoscopic physics and could offer huge technological potential as well. Here we report highly controlled fabrication of boron nanowire nanojunctions with unilateral feather-like morphology by radio-frequency magnetron sputtering of a boron and boron oxide mixture in argon atmosphere. The branched boron nanowires nucleated on the same sidewall of the stems, grew airwards, and aligned in parallel to form multiple T- and/or Y-type nanojunctions. The boron nanofeathers self-assembled into large-scale, highly ordered arrays on various substrates without the use of patterned catalysts. This process might enable the creation of nanometre-size heterojunctions of a wide variety of one-dimensional nanostructures.

We have numerically studied the band structure and the spin polarization effect in a periodic one-dimensional array of quantum point contacts (QPCs) formed in a two-dimensional electron gas in a plane-layered semiconductor system. In this study we used a self-consistent model developed within the framework of the Kohn–Sham local spin-density formalism. We have found that the band structure contains a mixture of flat and dispersed bands, and the role of transverse modes in the formation of such a band structure has been clearly demonstrated. We have also shown that spin polarization occurs mainly in the regions occupied by the QPCs and that it is qualitatively similar to the spin polarization in a single QPC.

We report on efficient blue organic light-emitting devices with an emission layer featuring a quasi-molecular quantum dot nanostructure as a charge carrier confining barrier, which was formed by doping a wide band gap molecule, 2-(2-hydroxyphenylbenzoxazole) lithium, into a newly synthesized blue host molecule, 9,10-bis-[4-(2,2-diphenylvinyl)-phenyl]-anthracene. The charge carrier confinement was greatly improved by doping with 10% wide band gap molecules, that led to a theoretical molecular quantum dot distance of 33 Å. The device showed enhanced efficiency () and good colour purity (x = 0.16,y = 0.15), while the projected device lifetime reached approximately 20 000 h at 150 cd m⁻².

The effects of single-walled carbon nanotubes on the polymerase chain reaction (PCR) were investigated via quantitative PCR product measurements, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (TEM) and x-ray photoelectron spectroscopy (XPS). The results showed that adding single-walled carbon nanotubes (SWCNTs) into the reaction liquid increases the amount of PCR product at SWCNT concentrations below 3 µg µl⁻¹, but this effect is reversed at higher SWCNT concentrations. Similar effects were observed in PCR reactions with or without Mg²⁺. Both SEM and HRTEM results showed that the DNA templates and Taq enzymes are attached to bundles of SWCNTs in PCR products. XPS results showed that the C 1s binding energy in PCR products increased after reaction, with the emergence of two new peaks beside the main peak compared with carbon nanotubes before reaction, suggesting that there might be a chemical reaction between SWCNTs and PCR components. In conclusion, SWCNTs may increase the PCR efficiency at a concentration range of less than 3 µg µl⁻¹ in the reaction liquid and have the potential to act as catalysts in a variety of biochemical reactions.

We describe a direct write technique using an electron beam to pattern ZrO₂ on a sub-10 nm scale that bypasses the conventional method of sputtering and lift-off. This technique utilizes spin-coatable ZrO₂ resist prepared by chemically reacting zirconium n-butoxide with benzoyl acetone in ethanol. The patterned resist has a sensitivity and contrast of and 3, respectively. Baking the resist at 85 °C increases the sensitivity to . The electron-beam-exposed regions become insoluble in acetone, thus yielding negative patterns. This property was exploited to write high-resolution patterns as small as 9 nm wide. Such negative patterns can be written with a pitch as close as 30 nm.

Photoinduced electron transfer in composites of CdSe and InP nanocrystals (NC) with a conjugated polymer [2-methoxy-5-(3-,7-dimethyl-octyloxy)-1, 4-phenylene vinylene] (OC₁C₁₀-PPV) is studied by means of light-induced electron spin resonance (LESR), photoluminescence (PL) as well as quasi steady-state photoinduced absorption (PIA) spectroscopy. The quenching of PL, the occurrence of two new optical absorption bands, and the formation of light-induced paramagnetic species on the polymer chain are altogether interpreted as an electron transfer between a donor polymer and acceptor NC in the excited state. In particular the LESR provides evidence of an electron transfer rather than energy transfer due to an overlap of absorption and emission bands of NC and the conjugated polymer. The g-factor of the signal is consistent with the cationic origin of OC₁C₁₀-PPV radicals. Additionally, the LESR signal is sensitive to NC surface coating being smaller in blends with the tri-n-octylphosphine oxide–tri-n-octylphosphine (TOPO–TOP) coated CdSe surface and completely absent in blends with TOPO–TOP–InP. LESR probes predominantly positive polarons on the conjugated polymer chain generated at room temperature in the course of an electron transfer to NC. This is very different from the situation in blends of OC₁C₁₀-PPV with fullerenes, another promising photovoltaic acceptor, where the photogenerated cation and anion were both observed in the LESR. In PIA we found contributions of both polymer polarons and electrons on the NC. The recombination kinetics shows a broad distribution of lifetimes, which is characteristic for dispersive (diffusive) recombination processes with fractional power frequency dependence.

Silver nanowires are prepared by electroplating into an anodic aluminium oxide (AAO) template. After the AAO template was removed by chemical etching, the surface of Ag nanowires was further modified by pulse DC electroplating. Various Ag nanobranches are grown on the surface of the Ag nanowire. This study discusses the influence of the pulse DC voltage and bias on the surface morphologies of Ag nanowires. The curvature of the nanowire surface is found to be the main factor in the growth of nanobranches. The surface morphology of the nanowire is adjustable by changing its growth rate. Radii of curvatures of the surfaces of approximately 33, 12 and 3 nm are obtained by electroplating at 1, 3 and 4 V DC voltages, respectively. The crystal size of a nanowire determined by x-ray diffraction analysis is almost independent of the growth conditions. Pulse DC electroplating conditions yield different growth rates of the nanobranch and create various surface morphologies of the nanowire. A more highly curved surface has a more localized charge and grows nanobranches faster. Surface roughness dominates the growth of nanobranches from silver nanowire.

The aligned growth of carbon nanofibres (CNFs) and carbon nanotubes (CNTs) via a simple sheath-dependent technique for orientation control is demonstrated. Significant difference in the alignment behaviour of CNFs/CNTs, involving the transition of sheath-dependent electric fields, is found to depend on the relation between the sheath width and the sample dimension. The electric field within the plasma sheath contributes to the aligned growth of CNFs/CNTs with an absolute orientation, and can be used to direct the assembly of CNFs/CNTs in a predetermined manner relative to the substrate by tilting the sample in a sheath region. The consequent application for synthesis of kinked carbon nanostructures by altering the alignment angle to the substrate during growth is also achieved.

An attempt is made to study the Einstein relation for the diffusivity–mobility ratio (DMR) in quantum wells (QWs) and quantum well wires (QWWs) of tetragonal compounds on the basis of a newly formulated electron energy spectrum taking into account the combined influences of the anisotropies in the effective electron mass, the spin–orbit splitting and the presence of crystal field splitting. The corresponding results for QWs and QWWs of III–V compounds form a special case of our generalized analysis. The DMR has also been studied for QWs and QWWs of II–VI and IV–VI materials. It has been found, taking QWs and QWWs of CdGeAs₂, InAs, CdS and PbSe as examples, that the DMR increases with increasing carrier degeneracy and decreasing film thickness in various oscillatory manners, emphasizing the influence of dimensional quantization and the energy band constants in different cases. An experimental method for determining the DMR in QWs and QWWs having arbitrary dispersion laws has also been suggested and the present simplified analysis is in agreement with the suggested relationship. The well-known results for QWs and QWWs of relatively wide gap materials having parabolic energy bands have also been obtained as special cases from this generalized analysis under certain limiting conditions.

Alumina nanowire arrays standing on the surface of a porous anodic alumina membrane have been achieved by first forming a porous anodic alumina membrane with parallel Y-branched nanochannels by reducing the applied anodizing voltage by a factor of in the anodization process of high-purity Al foil, and then chemically etching the Y-branched nanochannel alumina membrane in an aqueous phosphoric acid solution. The novel nanostructures may be used for two-dimensional photonic bandgap structural materials.

Nanoelectronic devices are anticipated to become exceedingly noisy as they are scaled towards thermodynamic limits. Hence the development of nanoscale classical information systems will require optimal schemes for reliable information processing in the presence of noise. We present a novel, highly noise-tolerant computer architecture based on the work of von Neumann that may enable the construction of reliable nanocomputers comprised of noisy gates. The fundamental principles of this technique of parallel restitution are parallel processing by redundant logic gates, parallelism in the interconnects between gate resources and intermittent signal restitution performed in parallel. The results of our mathematical model, verified by Monte Carlo simulations, show that nanoprocessors consisting of gates incorporating this technique can be made 90% reliable over 10 years of continuous operation with a gate error probability per actuation of and a redundancy of . This compares very favourably with corresponding results utilizing modular redundant architectures of with , and with no noise tolerance. Arbitrary reliability is possible within a noise limit of , with massive redundancy. We show parallel restitution to be a general paradigm applicable to different kinds of information processing, including neural communication. Significantly, we show how our treatment of para-restituted computation as a statistical ensemble coupled to a heat bath allows consideration of the computation entropy of logic gates, and tentatively sketch a thermodynamic theory of noisy computation that might set fundamental physical limits on scaling classical computation to the nanoscale. Our preliminary work indicates that classical computation may be confined to the macroscale by noise, quantum computation possibly being the only information processing possible at the extreme nanoscale.

Micro/nanomechanical characterization of the shell of a scallop, a member of the Pectinidae family, has been carried out. Hardness and elastic modulus were measured by nanoindentation using a nanoindenter. Micro/nanoscale cracks were generated by microindentation using a microindenter. The shell's crossed lamellar structure and indentation cracks were imaged using an optical microscope, an atomic force microscope and a scanning electron microscope. It was found from nanoindentation tests that the shell exhibits a hardness of about 5 GPa and elastic modulus of about 87 GPa. Nanoindentation resulted in pile-up around the indent. In the middle and bottom layers primary cracks propagate along the first-order lamellar boundaries and numerous secondary cracks branch off along the second-order lamellar boundaries. The additional energy required for crack propagation results from the secondary cracks along the second-order lamellar boundaries. Cracks formed in the top layer of the shell do not show the crack diversion mechanism due to the lack of first-order lamellar organization. Fracture mechanisms were discussed in conjunction with architecture, hardness, elastic modulus, and energy-dissipation during cracking.

Single-crystal Cu nanorods have been fabricated on carbon films by manipulating electron beam irradiation on a Cu powder charge in a transmission electron microscope (TEM). By adjusting the intensity of the electron beam, we observed lively nucleation and growth of the Cu nanorods with the TEM. Individual Cu nanorods are straight with diameters ranging from 40 to 50 nm. The length of the rods is controlled by e-beam irradiation duration, and can be extended to . Selective area electron diffraction showed that the sidewalls of the Cu nanorods were associated with the (110) planes, while facets on the tips were associated with the (111) planes. We believe that the growth process is mainly controlled by high surface mobility of Cu atoms on the C surface, and surface diffusion of the Cu atoms from high surface energy planes to low surface energy planes of the Cu nanorods.

Metal electrode structures for biosensors with a high spatial density and  nm gaps have been produced using focused megaelectronvolt (MeV) proton beam writing of poly-(methyl methacrylate) positive resist combined with metal lift-off. The minimal proximity exposure and straight proton trajectories in ( nm) resist layers for focused MeV proton beam writing are strongly indicative that ultimate electrode gap widths approaching a few nanometres are achievable.

Single-walled carbon nanotube (SWNT)/MgO composite films were fabricated by growing carbon nanotubes while simultaneously sintering a MgO film. The effect of iron and molybdenum concentrations in liquid catalysts and the effect of the density of carbon nanotubes in the composite films on the quality of the films were investigated. Microstructure analysis showed that SWNTs were uniformly grown in the MgO film. The presence of a controlled amount of carbon nanotubes in MgO films is believed to greatly improve the performance of the composite films as well as impart new functions. These MgO/nanotube composite films are expected to have a very high second-electron emission, which is very desirable for use in vacuum electronic devices.

A transmission electron microscopy examination of hydrothermally produced carbon nanofibres/nanotubes with outer diameter 50–200 nm suggests that the tube walls are inclined with respect to the tube axis. The apex angles are in the range 8°–16°. The structure of these tubes and their growth mechanism can be described by a conical-scroll model. The conical-scroll structure enables functionalization of both inner and outer tube surfaces. The outer wall of these nanofibres is shown to be covered by a hair-like layer, with a characteristic length of about 0.5 nm. Electron energy loss spectroscopy suggests that these 'hairs' are functional groups containing oxygen and carbon. The presence of these groups on the tube surface can account for the reported hydrophilic character of these tubes.

In this paper, results of the ageing of metal/ultra-thin oxide/semiconductor structures under Fowler–Nordheim constant current injections are presented. The oxide (silicon dioxide, SiO₂) thickness layer of these structures varies from 3 to 12.5 nm for a p-type semiconductor. It is shown that ageing induces trapped charges in the oxide layer (positive and negative near the cathode and positive near the anode) and new interface states at the oxide/semiconductor interface.

The positive charge created near the oxide/semiconductor interface, during current injection from the metal (accumulation regime, V_g<0), cannot be observed on current–voltage (I(V_g)) characteristics in the inversion regime (V_g>0). It is shown that these charges can trap electrons injected from the semiconductor during acquisition of the I(V_g) characteristics (V_g>0). This induces a shift in the I(V_g) characteristics as opposed to that what is obtained from capacity–voltage (C(V_g)) characteristics. So, the characteristics (density and centroid) of charges trapped in the oxide layer cannot be obtained, as in the case of thick layers (thickness greater than 20 nm), from the shift obtained from the I(V_g) characteristics in accumulation and inversion regimes. Also, it has been shown that the capture of electrons by the positive charge at the oxide/semiconductor interface promotes the creation of interface states.