Table of contents

The progress of electronic devices has been supported by advances in 'top-down' nanotechnology, namely lithography, which reached a scale of 90 nm on the mass production stage in 2005. The energy of the exposure source would exceed the ionization potential of the resist materials at the 32 nm scale with the deployment of extreme ultraviolet (EUV) light or an electron beam (EB). Among the issues of nanoscale fabrication with chemically amplified (CA) resists, line edge roughness (LER) is the most serious concern. Here, we report a Monte Carlo simulation of a latent image LER caused by ionization, in terms of proton dynamics, acid diffusion, and the effect of amine additives. The minimum LER (defined as three times the standard deviation) after post-exposure baking was ∼9.5 nm for a 5 µC cm⁻² exposure dose with 0.5 wt% amine. Although the deployment of a high-energy exposure source is the only method that allows further miniaturization after ArF immersion lithography, the acid generation mechanism, clarified for the first time in this paper, will emerge as a critical factor in limiting the availability of post-optical lithography.

Single-molecule imaging and spectroscopy using an aperture scanning near-field optical microscope operating at 1.8 K in a helium bath cryostat is demonstrated. From near-field images at constant excitation frequency, the orientation of single molecules can be deduced. Spectral information is obtained using both near-field and confocal excitation schemes by scanning the excitation frequency at a fixed sample position. Differences between near-field and confocal spectra are discussed in terms of the position with respect to the aperture and the molecular orientation.

An effective functionalization method was investigated to take full advantage of the exceptional performance of both carbon nanotubes and epoxy polymer for composite application. Epoxy polymer curing agent, EPI-W, was grafted to the single-walled carbon nanotubes through diazotization. Fourier transformed infrared spectroscopy, Raman spectroscopy, differential scanning calorimetry, dynamical mechanical analysis and thermo-gravimetric analysis were performed to characterize the functionalization effect. The degree of functionalization was estimated to be 1 in 50 carbons in the nanotube framework. The elastic modulus of the nanocomposite was enhanced 24.6% with only 0.5 wt% loading of functionalized carbon nanotubes, in contrast to the 3.2% increase of un-functionalized carbon nanotube reinforced composite. This significant improvement suggested an effective way to realize an industrial application of nanotubes reinforcing epoxy composite.

Nylon-4,6 nanofibres with diameters ranging from about 1 µm down to 1 nm were prepared by electrospinning. The fibre diameter was varied by adjusting the concentration of the polymer solution. Electrospinning of a concentrated solution of as high as 20% nylon-4,6 by weight in formic acid produced a ribbon-like electrospun fibre with a ribbon width of about 850 nm. A semi-dilute concentration of 2% nylon-4,6 by weight produced the thinnest nylon-4,6 nanofibres with diameters of 1.6 nm or less. A small amount of pyridine was added to the electrospinning solution to avoid the formation of beaded nanofibres in the course of electrospinning at low concentrations. Scanning and transmission electron microscopy were used to characterize the size of the nanofibres. An ultra-thin nylon-4,6 nanofibre of 1.2 nm diameter might contain six or seven nylon-4,6 molecules in a typical cross-section of the fibre.

The secondary electron emission (SEE) of ZnO-coated carbon nanotubes (CNTs) was measured using a biasing technique in a scanning electron microscope. The SEE yield of the ZnO-coated CNTs is higher than that of the ZnO film deposited on Si substrates. Direct observation of the variation in SEE from tip-end and non-CNT positions was demonstrated. Local measurement reveals that the SEE yield at the tip-end of the ZnO-coated CNTs is much higher than that of non-CNT positions. The enhancement of SEE is attributed to the strong local field generated at the tip of the CNTs.

Ordered growth of 3,4,9,10-perylene-tetracarboxylic-dianhydride (PTCDA) on Ag(111) partially covered by one or two monolayers of KBr was investigated by non-contact AFM with molecular resolution. Different adsorption patterns are found on the pure substrate, the one covered by a single monolayer, and the one covered by two monolayers KBr. Simulations with an extended Ising-type model reproduce these experimental patterns very well. The adsorbate–adsorbate and the adsorbate–substrate interaction parameters obtained from the simulation are discussed with respect to the interactions at the Ag(111)|KBr interface. As a result, alkali halide covered metals can be used for tuning the interactions and designing adsorption systems, which opens up new possibilities in the control of self-assembled nanostructures.

Scanning probe imaging is often limited by disturbances, or mechanical noise, from the environment that couple into the microscope. We demonstrate, on a modified commercial atomic force microscope, that adding an interferometer as a secondary sensor to measure the separation between the base of the cantilever and the sample during conventional feedback scanning can result in real-time images with inherently suppressed out-of-plane disturbances. The modified microscope has the ability to resolve nanometre-scale features in situations where out-of-plane disturbances are comparable to, or even several orders of magnitude greater than, the scale of the topography. We present images of DNA in air from this microscope in tapping mode without vibration isolation, and show improved clarity using the interferometer as the imaging signal. The inherent disturbance suppression approach is applicable to all scanning probe imaging techniques.

The formation and photoluminescence (PL) of InP nanowires grown by metal organic vapour phase epitaxy on InP(111)B substrates, using colloidal gold nanoparticles as catalysts, are investigated. The dependence of the orientation and dimensions of the nanowires on the growth temperature is studied using scanning electron microscopy. Vertically aligned oriented nanowires with a mean base diameter in the range 50–150 nm, and a tip diameter of 50 nm, show a PL blue-shift of about 80 meV compared to the substrate. Blue-shift due to quantum confinement is ruled out because of the large diameter of the nanowires. A clear correlation between the orientation of the nanowires on the substrate and the PL peak position is observed. Based on x-ray diffraction and transmission electron microscopy measurements, it is proposed that the as-grown vertically oriented nanowires have crystallized in the wurtzite lattice instead of in the zinc-blende structure, which results in a blue-shifted PL.

Samples of rutile TiO₂ have been prepared by sintering compacted powders under argon flow. Long (above 20 h) sintering times at 1500 °C led to the formation of rods with squared cross-sections in a broad range of sizes. A two-step annealing treatment, at two temperatures, was found to favour the growth of low-dimensional elongated structures as well as a terraced structure on the grain surface, producing samples with high surface to volume ratio. The cathodoluminescence (CL) spectrum of the initial powder, shows an emission centred at about 2.40 eV, which can be separated into three Gaussian bands at 2.19, 2.30 and 2.55 eV. The main features of the CL spectra of sintered samples are an infrared band at 1.52 eV and a complex band in the visible range, whose peak position shifts with the annealing temperature. In samples sintered for 30 h an emission at 1.80 eV appears, while the dominant emission at 1.52 eV, due to titanium interstitials, is quenched.

In this work, we developed a convenient and efficient method for solubilization, purification and functionalization of carbon nanotubes (CNTs) using a versatile reagent (phosphotungstic acid (HPW)). Because HPW can spontaneously attach to graphite walls as polyanions and provide static repulsion, CNT aggregates were divided into individual and small bundles of CNTs and turned into a stable solution by sonication in the presence of HPW. Amorphous carbon impurities and metal catalysts in the raw CNTs were removed by centrifugation and filtration. Finally, purified CNTs with a yield of 82 wt% were obtained. Using HPW on graphite walls as an electrostatic and acid anchor, positively charged titania nanoparticles and albumin molecules were successfully assembled around CNTs without altering their delocalized π-electron system. The versatility of this simple approach could be extended beyond inorganic nanoparticles and proteins, to other systems with desired properties.

Highly uniform Fe nanoring arrays in porous anodic alumina templates are fabricated by physical vapour deposition and grazing ion milling techniques. The nanorings have aspect ratios ranging from 0.8 to 4, depending on the deposition conditions. The outer diameter of the individual nanorings, and the area density and distribution patterns are completely determined by the template used. Selected-area electron diffraction reveals that these nanorings have a polycrystalline microstructure. The nanoring fabrication method demonstrated here can be extended to other materials.

Uniform platinum nanodendrites have been prepared at a water/oil interface by a facile catalyst-free method at room temperature. This is carried out by introducing NaBH₄ into the platinum precursor solution in the presence of the second generation of carboxyl-cored dendrimer ([G-2]-CO₂H dendrimer) and toluene to act as a protective agent and a linker, respectively. The average fractal dimension of 1.61 of the obtained platinum nanodendrites is calculated by analysing the transmission electron micrographs using the programs Fractal Dimension Version 1.1 and Fractal Dimension Calculator. Control experiments show that the fabrication of platinum nanodendrites can be operated with a wide parameter window, which undoubtedly raises the degree of control of the synthesis process. The potential application of such a nanostructure as a catalyst is investigated, and the results reveal that they show highly efficient catalytic properties for the typical redox reaction between hexacyanoferrate (III) and thiosulfate ions at 301 K.

A microsquare fabrication process is developed for the investigation of the processing characteristics of boron nitride and carbon (C/BN)_n and (BN/C)_n films with a 4 nm nanoperiod multilayer structure. Simultaneous surface topography, friction and current measurements were performed on the multilayer films by conductive atomic force microscopy (AFM) with force modulation, which permits the quantitative recording of current and frictional force as functions of the applied force. The current image showed that highly conducting sites formed on carbon (C) layers and that nonconducting sites existed on boron nitride (BN) layers and/or mixed layers. Furthermore, amplitude response (friction force) images show that the conducting sites have a low frictional force, whereas the nonconducting sites have a high frictional force. This is thought to be due to the structure phase of the nanostructure of the films. Further, the result that the nonconducting sites have a high amplitude response (friction) implies the existence of a mixed layer (interface) between the C and BN layers. It is suggested that friction and surface-current measurements are effective methods of investigating multilayer nanostructural surfaces and fabricating micro-electro-mechanical processing systems of a high precision.

Frequency-dependent dynamic behaviour in piezoresponse force microscopy (PFM) implemented on a beam-deflection atomic force microscope (AFM) is analysed using a combination of modelling and experimental measurements. The PFM signal is comprised of contributions from local electrostatic forces acting on the tip, distributed forces acting on the cantilever, and three components of the electromechanical response vector. These interactions result in the flexural and torsional oscillations of the cantilever, detected as vertical and lateral PFM signals. The relative magnitudes of these contributions depend on geometric parameters of the system, on the stiffnesses and frictional forces of the tip–surface junction, and on the frequency of operation. The dynamic signal formation mechanism in PFM is analysed and conditions for optimal PFM imaging are formulated. An experimental approach for probing cantilever dynamics using frequency–bias spectroscopy and deconvolution of electromechanical and electrostatic contrast is implemented.

We investigate the effect of lattice geometry on the magnetic anisotropy and transport properties of Ni₈₀Fe₂₀ antidot nanostructures. The structures were fabricated using deep ultra-violet lithography at 248 nm exposure wavelength. For an antidot array with a square lattice, a fourfold magnetic anisotropy with alternating hard axis and easy axis every 45° was observed. The honeycomb and rhomboid antidot lattice, however, both show a sixfold anisotropy, conforming well to the symmetry of their respective lattices. The magnetic hysteresis and micromagnetic simulation of the spin states at remanence show that the magnetization reversal process is very sensitive to the lattice arrangement of the holes. From the magnetotransport measurements, both the current density distribution and the magnetoresistance behaviour are markedly dependent on the antidot lattice geometry, in agreement with our transport simulations.

The energetic, electronic and structural properties of a heterojunction formed by BN and AlN (10,0) nanotubes have been studied using first principles density functional theory. The differences between the AlN and BN nanotubes lead to structural rearrangements mainly at the junction layers. Two different types of junction occur, and net charges of opposite signs appear in each of them, with a resulting electric dipole along the heterojunction axis. The calculated band offset shows a staggered band line-up, with the heterojunction forming a one-dimensional array of quantum dots.

GdF₃:Eu³⁺ nanocrystals (NCs) and nanorods were synthesized by a microemulsion-mediated hydrothermal process. The structure, shape and particle size were characterized by means of x-ray diffraction (XRD) and transmission electron microscopy (TEM). The vacuum ultraviolet (VUV) spectrum of GdF₃:Eu³⁺ NCs shows that the Gd³⁺ ion can absorb one VUV photon excited in the ⁶G_J levels and relaxes through two-step energy transfer to Eu³⁺, yielding two visible photons at room temperature. The visible quantum efficiency of GdF₃:Eu³⁺ NCs was calculated to be close to 170% by the peak intensity ratio of correlative transition emission under VUV excitation at 160 nm.

InAs mid-infrared emissive quantum dots (QDs) grown on a graded In_xGa_1−xAs/InP matrix with more uniform size and higher dot density have been successfully prepared by low pressure metal organic chemical vapour deposition (LP-MOCVD) under safer growth conditions. Low toxic tertiarybutylarsine and tertiarybutylphosphine sources were used to replace the high toxic arsine and phosphine in the MOCVD growth. To improve the process safety further, inertial N₂ instead of the normally used explosive H₂ was used as the carrier gas. Initially, by using a two-step growth method, uniform InAs QDs with a high dot density of 1.3 × 10¹⁰ cm⁻² have been successfully grown on a InGaAs/InP matrix. The emission wavelength of the QDs reaches >2.1 µm. The low temperature photoluminescence spectrum of the QDs grown by the two-step growth has much narrower linewidth and higher intensity than that of the QDs grown by using normal Stranski–Krastanow (S–K) and atomic layer epitaxy (ALE) growth methods.

We prepared ordered sub-100 nm pseudo-spin-valve (PSV) element arrays by electrodeposition of NiFe/Cu/Co into the pores of self-organized nanoporous anodized aluminium templates. Field-emission scanning electron microscopy reveals that the sub-100 nm PSV arrays, of uniform size, are well separated and exhibit a perfect two-dimensional array with a hexagonal pattern. The easy-axis hysteresis loops show two distinct steps related to the separate reversal of soft (NiFe) and hard (Co) layers. The switching fields of the PSV arrays are approximately −50 Oe for the NiFe and 570 Oe for the Co. The dependence of the magnetoresistance on the Cu spacer layer thickness indicates the presence of an oscillatory interlayer exchange coupling through the Cu layers.

We present a novel model of the effective thermal conductivity for carbon nanotube composites by incorporating the interface thermal resistance with an average polarization theory. The dependence of the effective thermal conductivity on nanotube length, diameter, concentration, and interface thermal resistance has been taken care of simultaneously in our treatment. The model predicts that the large length of the carbon nanotubes embedded plays a key role in the thermal conductivity enhancement, while the large interface thermal resistance across the nanotube–matrix interface causes a significant degradation. Interestingly, the model predicts that the nanotube diameter has a very small effect on the thermal conductivity enhancement of the nanotube composites. In addition, the model predicts that the thermal conductivity enhancement of nanotube composites increases rapidly with decreasing the thermal conductivity of the matrix and increases with increasing the thermal conductivity of the carbon nanotube. Predictions from the novel model are in excellent agreement with the experimentally observed values of the effective thermal conductivity of carbon nanotube nanofluids which the classical models have not been able to explain.

A facile strategy for fabricating polypyrrole–chitosan (PPy–CS) hollow nanostructures with different shapes (sphere, cube and plate) and a wide range of sizes (from 35 to 600 nm) is described. These hollow structures have been fabricated using silver bromide as a single template material for polymer nucleation and growth. PPy–CS hollow nanostructures are formed by reaction with an etching agent to remove the core. These hollow nanostructures have been extensively characterized using various techniques such as TEM, FT-IR, UV–vis, and XRD.

Copper nanoparticles with a mean carbon coating of about 1 nm were continuously produced at up to 10 g h⁻¹ using a modified flame spray synthesis unit under highly reducing conditions. Raman spectroscopy and solid state ¹³C magic angle spinning nuclear magnetic resonance spectroscopy revealed that the thin carbon layer consisted of a sp²-hybridized carbon modification in the form of graphene stacks. The carbon layer protected the copper nanoparticles from oxidation in air. Bulk pills of pressed carbon/copper nanoparticles displayed a highly pressure- and temperature-dependent electrical conductivity with sensitivity at least comparable to commercial materials. These properties suggest the use of thin carbon/copper nanocomposites as novel, low-cost sensor materials and offer a metal-based alternative to the currently used brittle oxidic spinels or perovskites.

A mathematical model for the evaporation of micro- and nano-sized solution droplets is developed. This model is used to predict whether the particles produced by spray drying and pyrolysis are fully filled or hollow. The model includes the non-continuum effects on the droplet evaporation. This is achieved by combining an interpolation formula based on the numerical solution of the Boltzmann equation for the transition regime with the continuum based governing equations. Results show that the non-continuum effects can be significant for the evaporation of submicron and nano-sized droplets in atmospheric pressures. Correlations for the final particle size and its wall thickness in terms of reactor temperature and pressure and the initial solution concentration are developed. The predictions are in good agreement with experiments performed on the submicron zirconia particles, prepared by spray pyrolysis.

The departure from perfect spherical symmetry in the case of fullerenes (C₆₀ being the sole exception) induces instabilities due to the stresses generated by the pentagonal protrusions in the σ-bonded surfaces. By assuming σ–π separability and treating π electrons as a degenerate Fermi gas in the two shells around the central σ structure, the resulting degeneracy pressures can further enhance the σ-surface initiated instabilities for non-icosahedral structures (especially for those <C₆₀) as well as the icosahedral fullerenes (>C₆₀) with large protrusions. Under certain circumstances the net degeneracy pressure across the σ surface may have a structure stabilizing effect. The role of the π-electron degeneracy in a broad range of fullerenes from C₂₀ to C₁₅₀₀ and its effects on fullerene stability are investigated.

Ultra-long rutile tin dioxide nanowires and nanobelts are synthesized by thermal oxidation of tin powder using gold film as the catalyst. Nanowire or nanobelts can be selectively produced by tuning the reaction temperature. The vapour–liquid–solid growth mechanism is proposed. The band gaps of the nanowires and nanobelts are 3.74 and 3.81 eV respectively, determined from UV/visible absorption spectral results. The SnO₂ nanowires show stable photoluminescence with two emission peaks centred at around 470 and 560 nm. Their wavelengths stay almost fixed while their intensities depend sensitively on the temperatures within the examination ranges from 10 to 300 K. The SnO₂ nanobelts show similar photoluminescence behaviours and the origin of the luminescence is discussed.

Bi₂Se₃ nanorods have been synthesized through a simple hydrothermal reduction approach. The nanorods formed were ≈10 nm in diameter and 100–200 nm in length. XRD characterization suggested that the product consisted of the hexagonal phase of pure Bi₂Se₃. EDX and XPS studies further confirmed the composition and purity of the product. A possible mechanism for the reaction is proposed, where Bi₂Se₃ microsheets are presumed to be the intermediate for the formation of the nanorods. The effect of solvent on the morphology of the final product is discussed, where, in the presence of aprotic solvent DMF, nanoparticle formation is observed. A bandgap of 2.25 eV is observed from the UV–visible absorption spectra.

Thermoelectric material Bi₂Te₃ nanowire arrays have been successfully prepared by pulsed electrochemical deposition into the nanochannels of porous anodic alumina membranes. X-ray diffraction analyses show that the as-synthesized nanowires have a highly preferential orientation. Scanning electron microscopy, transmission electron microscopy, and high-resolution transmission electron microscopy observations indicate that the high-filling-rate and uniform Bi₂Te₃ nanowires are single crystalline. Energy dispersive spectrometer analyses indicate that the compositions of the nanowires can be controlled by changing the potentials and the solution concentrations. The electrical resistance measurements indicate that the resistances increase with decreasing temperature and show a typical semiconductor characteristic. The growth mechanism is discussed together with the electrochemical deposition process studies.

Self-assembled InGaN quantum dots (QDs) were grown by metal–organic chemical vapour deposition with growth interruption at low V/III ratio and low growth temperature on sapphire substrates. The effects of the interruption time on the morphological and optical properties of InGaN QDs were studied. The results show that the growth interruption can modify the dimension and distribution of InGaN QDs, and cause the QD emission wavelength to blue shift with increasing interruption time. A density of InGaN QDs of about 4.5 × 10¹⁰ cm⁻² with an average lateral size of 11.5 nm and an average height of 1.6 nm can be obtained by using a growth interruption time of 60 s.

We report a method to improve the efficiency of surface-enhanced Raman scattering (SERS) from a silver oxide film. A 632.8 nm He–Ne laser beam was focused on silver oxide films deposited on different substrates (silica, TiO₂, Si). We found that the substrate material greatly affected the SERS efficiency, and that silica substrate showed the highest efficiency among the materials measured. Scanning electron microscopy observations revealed that silver nanoparticles were generated within the focused laser spot. Computer simulations of the thermal profile based upon data from experimental observations were also carried out. It was found that the temperature of the silver oxide film differed greatly according to the substrate. We infer that substrates that allow higher silver-oxide-film temperatures to be attained are more suitable for efficient SERS.

A parametric study was carried out on a novel carbon nanotube (CNT) synthesis using 'arc-discharge in solution' (ADS). The carbon nanostructure yield as a function of time, the rate of erosion of the anode, and the rate of deposition of carbonaceous materials on the cathode electrode were investigated. Amperage dependent normalized kinetic parameters were evaluated. The production rate of carbon nanostructures including CNTs at 75 A is as high as 5.89 ± 0.28 g min⁻¹. Thermogravimetric analysis and x-ray diffraction studies reveal high purity of the carbon nanostructures collected from water and have a very good agreement with electron microscopy analyses. Very high surface area of the pristine multiwalled CNTs and nanostructures (84 ± 3.5 m² g⁻¹) was measured using BET. The dynamic light scattering (DLS) analysis shows further agreement with the amperage dependent studies.

Lanthanum and niobium doped PZT with composition (Pb_0.93La_0.07)[(Zr_0.60Ti_0.40)]_0.9825Nb_0.0175O₃ (PZTLN) was prepared by the gel-combustion method. A precursor sol was obtained from lead nitrate, zirconyl nitrate, lanthanum oxide, peroxo-citrato-niobium and a peroxo-citrate complex of titanium isopropoxide as starting precursors. Various molar ratios of citrate/nitrate (CA/NO₃⁻ = 1.3, 0.36 and 0.09) were used to prepare very fine powders of PZTLN. The gels resulting from these sols were transformed into powders by an auto-combustion process at ≤400 °C. The powders consisted of rhombohedral PZT (PbZr_0.60Ti_0.40O₃), pyrochlore (Pb₂Ti₂O₆) and lead carbonate (Pb₂O·CO₃) phases. The pure rhombohedral phase is found in PZTLN pellets sintered at 1100 °C for all citrate/nitrate ratios. Titanium and niobium precursors were modified with peroxo radicals. During the gel-combustion reaction, the temperature of the gel increases, leading to lead evaporation. The loss of lead as well as the particle size increases as the CA/NO₃⁻ ratio decreases. The smallest grained powder (about 50 nm) was obtained with the ratio CA/NO₃⁻ equal to 0.09.

This paper reports the synthesis of well-aligned copper nanowires using an electrochemical deposition template technique. The electrical properties of copper nanowire arrays synthesized within vertical pores of alumina template were measured using a current-sensing atomic force microscope (AFM), with bias voltage applied between the AFM tip and the gold back-electrode. Nonlinear current–voltage (I–V) characteristics of copper nanowire arrays are observed; this is attributed to the impurities near the wire–lead contact region. These vertical copper nanowire arrays are suitable for use in fabricating nanoelectronic devices.

Tubular ZnO microstructural arrays were fabricated by a hydrothermal decomposition method. The dependence of the morphologies on the growth time and temperature was investigated in detail. An experiment was carried out to determine the mechanism of tubular ZnO formation. Our results showed that ZnO microtubes originated from an ageing process from ZnO microrods at a lower temperature (compared to the temperature when hydrothermal deposition of ZnO microrods was dominant) due to the preferential chemical dissolution of the metastable Zn-rich (0001) polar surfaces. A growth model was proposed based on the coexistence of hydrothermal deposition and dissolution of ZnO in the fabrication process.

Gd₂O₃:Eu³⁺ and Gd₂Ti₂O₇:Eu³⁺ films 10 nm in thickness were individually coated onto silica spheres (particle size of 150–170 nm) using the sol–gel method. The synthesized materials were addressed as Gd₂O₃:Eu³⁺@SiO₂ and Gd₂Ti₂O₇:Eu³⁺@SiO₂ phosphors. An x-ray powder diffractometer (XRD), field emission scanning electron microscope (FE-SEM), high-resolution transmission electron microscope (HR-TEM), and photoluminescence spectrophotometer (PL) were employed to characterize the core–shell phosphors. Uniform core–shell phosphor particles were observed using FE-SEM. The XRD and HR-TEM results indicated that the coated-shell layer was well crystallized after sintering at 1000 °C. The Gd₂O₃:Eu³⁺@SiO₂ PL measurement showed a red emission at the main 615 nm wavelength. The Gd₂Ti₂O₇:Eu³⁺@SiO₂ phosphor showed an orange–red emission at the 588 and 615 nm wavelengths. In comparison with the Gd₂O₃:Eu³⁺ and Gd₂Ti₂O₇:Eu³⁺ bulk material results, the core–shell phosphors maintained the same emission ability as the bulk materials and the novel core–shell phosphors possessed great potential in quantum phosphor applications.

Current versus voltage characteristics (I–V) of nanocrystalline SnO₂ materials have been investigated in air at room temperature. The samples were prepared by the inert gas condensation technique (IGCT) as well as by chemical methods. X-ray diffraction studies showed a tetragonal rutile structure for all the samples. Microstructural studies were performed with transmission electron microscopy. All the samples exhibited nonlinear I–V characteristics of the current-controlled negative resistance (CCNR) type. The results show that the threshold field (break down) voltage is higher for the samples prepared by the IGCT method than for those prepared by the chemical method due to the formation of a tin oxide layer over the crystalline tin. It is also found that the threshold field increases with the decrease in grain size.

This work investigates the critical issues in the focused ion beam (FIB) nanopatterning of semiconducting devices. Matrixes of holes with diameter of about 150 nm were drilled by FIB on the topmost layers of a quantum dot based device. In order to study the presence of artefacts in the active region of the device, the milling parameters were investigated. A careful analysis of the ion beam effects on the structural and morphological features of the holes, mainly due to the heterogeneous composition of the layers to be milled, demonstrated that important deviations from the expected structures, in terms of size, shape and geometry of the holes, as well as layer amorphization and damage, occur.

A general and template-free 'disproportionation and reversal' route was developed to synthesize one-dimensional (1D) nanostructures of Te, Se and Se–Te alloys directly from Te or/and Se powders. The products were characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and scanning electron microscopy (SEM). Te nanorods and nanowires with a width varying from about 40 nm to about 300 nm, Se nanowires with a width of 60–100 nm and a length of 4–6 µm, and Se_xTe_100−x alloy nanorods with x in a wide range, and with a width of 30–70 nm and an aspect ratio of three to five, were prepared. The mechanism of formation of the nanorods and nanowires and the effects of the experimental conditions, such as solution concentration, cooling rate, solvent nature and heating process, on the morphology and size of the products have been discussed. We believe that this general route and some other proper reversible processes between solid state and solution state can be extended to the transformations from various bulk materials into nanosized materials with various morphologies.

A unique combination of acid treatment, aqueous colloidal processing, and spark-plasma sintering (SPS) has been used to fabricate high-density Al₂O₃ /single-wall carbon nanotube (SWNT) composites with well-distributed SWNTs and other carbon nanostructures ('nano-onions', diamond) at Al₂O₃ grain boundaries. This approach could be used to obtain well-controlled microstructures of ceramic/SWNT composites for tailored mechanical, electrical, and thermal properties. In addition, the colloidal approach for dispersing SWNTs presented here could be used for the controlled manipulation of SWNTs.

In this paper, a hybrid device based on a microcantilever interfaced with bacteriorhodopsin (bR) is constructed. The microcantilever, on which the highly oriented bR film is self-assembled, undergoes controllable and reversible bending when the light-driven proton pump protein, bR, on the microcantilever surface is activated by visible light. Several control experiments are carried out to preclude the influence of heat and photothermal effects. It is shown that the nanomechanical motion is induced by the resulting gradient of protons, which are transported from the KCl solution on the cytoplasmic side of the bR film towards the extracellular side of the bR film. Along with a simple physical interpretation, the microfabricated cantilever interfaced with the organized molecular film of bR can simulate the natural machinery in converting solar energy to mechanical energy.

Hollow zinc oxide microspheres have been synthesized from a micro ZnBr₂·2H₂O precursor obtained by an autoclave process in bromoform steam at 220 °C /2.5 MPa. Field-emission scanning electron microscropy (FE-SEM) and transmission electron microscopy (TEM) show that the products are about 1.0 µm single crystal spherical particles with hollow interiors, partly open surfaces and walls self-assembled by ZnO nanoparticles. X-ray diffraction (XRD) analysis shows that the as-prepared ZnO hollow spheres are of a hexagonal phase structure. A possible formation mechanism is suggested on the basis of the shape evolution of ZnO nanostructures observed by SEM and TEM. The room-temperature photoluminescence (PL) spectrum shows UV emission around 386 nm and weak green emission peaks indicating that there are few defects in the single crystal grains of the ZnO microspheres.

Bovine serum albumin (BSA) microspheres incorporated with CdTe quantum dots (QDs) have been prepared via a spray-drying and thermal-denaturizing approach. The results show that the morphology of the composites obtained was greatly affected by the inlet temperature and the initial concentration of BSA in the precursor. Most of the composites prepared with 0.6 mM BSA in the precursor at 40 °C were spherical in shape and hollow. The thermal-denaturized microspheres were water-insoluble, and separated from each other after dispersing in water. Each microsphere had bright fluorescence with pure colour. The microspheres without thermal-denaturation dissolved easily in water, and released nanospheres (>8 nm) that consisted of many CdTe nanoparticles (<3 nm). This approach opens the possibility of rapidly preparing QDs microspheres with controlled fluorescence intensity or with separated multiemission peaks for biomedical applications.

For the first time, single crystalline Ni nanosheets have been successfully synthesized with the aid of iron species. The as-prepared nanosheets are mainly triangular and hexagonal in shape, with edge lengths ranging from several tens to several hundreds of nanometres. The exposed sheet planes are assigned to be (111) planes of a face-centred cubic nickel crystal. The well defined geometry enhances the anisotropic energy of Ni nanosheets, and therefore increases its blocking temperature (T_B) to room temperature. Notably, the coercive force of the Ni nanosheets is 172 Oe at 300 K, which is significantly higher than that of the bulk one (ca. 0.7 Oe at room temperature). A possible mechanism is proposed to explain the formation of the thermodynamically unfavorable morphology of nanosheets. We suggest that crystal twinning, which is formed by etching of the introduced iron species with oleic acid, lowers the system energy, and leads to the growth of these Ni nanosheets.

A recent article (Miwa et al 2005 Nanotechnology 16 2427) casts doubt on the four-dimer-wide Haiku model for the Bi nanoline on Si(001), suggesting instead that the three-dimer-wide Miki model (which had been ruled out) is a better fit in particular to x-ray data. The reasons why the Haiku model provides the best fit to all published data among currently proposed structures are discussed, concentrating on the width and registry of the Bi nanoline, and mentioning new data which shows that under appropriate conditions the two structures coexist in the same surface.

The registry of bismuth dimers, integral components of the bismuth nanoline on Si(001), is examined. In contrast to the currently accepted view, the bismuth dimers are found to be in registry with the two-dimensional lattice created by the silicon dimers. The consequences of this finding are briefly explored.

The review that was allocated pages R41–R56 has been withdrawn at a late stage. If you have already downloaded this paper, please consider it unpublished. If you have any queries, please contact nano@iop.org.