Tens Of Μm Research Articles

Development of micro-beam NRA for 3D-mapping of hydrogen distribution in solids: Application of tapered glass capillary to 6 MeV 15N ion

A micro-beam NRA system, by means of a resonant nuclear reaction 1H(15N, αγ)12C, has been developed for the purpose of the 3D mapping of the hydrogen distribution in solids. To obtain the tens μm size of the beam spot, the combination of the newly proposed tapered glass capillary and a conventional quadrupole magnetic lens is employed. An Y patterned film on a substrate is prepared as an application of the developed system. The 6MeV 15N beam focused by glass capillaries down to 50μm successfully shows the hydrogen distribution. The in-plane NRA profile implies that the beam emitted from the glass capillary outlet is parallel, although the original beam has a considerable divergence. The NRA measurements in the 103Pa N2 atmosphere due to the low gas conductance of the glass capillary is also demonstrated.

Acoustic charge and spin transport in GaAs quantum wires

AbstractOptical investigation of the transport of electrons and holes in GaAs quantum wires by surface acoustic waves shows that carriers can be efficiently transported over several tens of mm. Despite the efficient charge transport, the transport distances for photoexcited spins were found to be very short.These short spin transport lengths indicate that spin dephasing is not limited by spin motion (the DP mechanism) but rather by spin relaxation during momentum scattering. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Hydrogen isotope fractionation by Methanothermobacter thermoautotrophicus in coculture and pure culture conditions

We grew a hydrogen-utilizing methanogen, Methanothermobacter thermoautotrophicus strain ΔH, in coculture and pure culture conditions to evaluate the hydrogen isotope fractionation associated with carbonate reduction under low (< several tens of μM; coculture) and high (>6 mM; pure culture) concentrations of H 2 in the headspace. In the cocultures, which were grown at 55 °C with a thermophilic butyrate-oxidizing syntroph, the hydrogen isotopic relationship between methane and water was well represented by the following equation: δ D CH 4 = 0.725 ( ± 0.003 ) · δ D H 2 O - 275 ( ± 3 ) , in which the hydrogen isotope fractionation factor ( α H) was 0.725 ± 0.003. The relationship was consistent with the isotopic data on methane and water from terrestrial fields (a peat bog in Washington State, USA, and a sandy aquifer in Denmark), where carbonate reduction was reported to be the dominant pathway of methanogenesis. In the pure cultures, grown at 55 and 65 °C, the α H values were 0.755 ± 0.014 and 0.749 ± 0.014, respectively. Dependence of α H on growth temperature was not observed. The α H value at 55 °C in the pure culture was slightly higher than that in the coculture, a finding that disagrees with a hypothesis proposed by Burke [Burke, Jr. R. A. (1993) Possible influence of hydrogen concentration on microbial methane stable hydrogen isotopic composition. Chemosphere 26, 55–67] that hydrogen isotope fractionation between methane and water increases (and α H decreases) with increasing H 2 concentration.

Depth profiling of carbon in silicon using the 12C(p, p′γ) reaction

An analytical method has been developed for the measurement of a carbon depth profile of the region a few tens of μm from the surface, using a 12C(p,p′γ) reaction. Measurements for a SiC sample coated with a silicon layer and a carbon-implanted silicon sample were performed using this method. Two charged particle detectors and two γ-ray detectors were utilized for the coincident detection of scattered protons and γ-rays from the first excited state (Ex=4.4MeV) of 12C. The measured depth profiles agree well with results obtained using a surface profiler and an Auger microprobe. These results demonstrate that this method is useful for the non-destructive analysis of carbon at depths of a few tens of μm from the surface.

Fabrication of micro-dot arrays and micro-walls of acrylic acid/melamine resin on aluminum by AFM probe processing and electrophoretic coating

Micro-dot arrays and micro-walls of acrylic acid/melamine resin were fabricated on aluminum by anodizing, atomic force microscope (AFM) probe processing, and electrophoretic deposition. Barrier type anodic oxide films of 15 nm thickness were formed on aluminum and then the specimen was scratched with an AFM probe in a solution containing acrylic acid/melamine resin nano-particles to remove the anodic oxide film locally. After scratching, the specimen was anodically polarized to deposit acrylic acid/melamine resin electrophoretically at the film-removed area. The resin deposited on the specimen was finally cured by heating. It was found that scratching with the AFM probe on open circuit leads to the contamination of the probe with resin, due to positive shifts in the potential during scratching. Scratching of the specimen under potentiostatic conditions at −1.0 V, however, resulted in successful resin deposition at the film-removed area without probe contamination. The rate of resin deposition increased as the specimen potential becomes more positive during electrophoretic deposition. Arrays of resin dots with a few to several tens μm diameter and 100–1000 nm height, and resin walls with 100–1000 nm height and 1 μm width were obtained on specimens by successive anodizing, probe processing, and electrophoretic deposition.

Effects of Compatibility of Acrylic Block Copolymer and Tackifier on Phase Structure and Peel Adhesion of Their Blend

The effect of compatibility of polymer and tackifier on the adhesion properties of pressure-sensitive adhesive tape was investigated. For this purpose, a model pressure-sensitive adhesive tape was prepared. A mixture of poly(methyl methacrylate)-block-poly(butyl acrylate)-block-poly(methyl methacrylate) triblock copolymer and a similar diblock copolymer was used as the base polymer. And three kinds of tackifiers, namely a rosin phenolic resin (A), a special rosin ester resin (B) and a hydrogenated cycloaliphatic resin (C) were used. The compatibility with the base polymer was in the order of tackifier A > B > C. Transmission electron microscopy studies confirmed that the tackifier A had good compatibility, where agglomerates of the tackifier with a size of about 10 nm only were observed. Larger and distinct agglomerates of tackifier were observed for tackifier B and the size increased with the tackifier content. The tackifier C formed domains with a mean size of several tens μm. Dynamic mechanical analysis indicated that both the glass transition temperature and modulus increased at low temperature and the modulus at high temperature decreased by the addition of tackifier for tackifiers A and B. This tendency was more remarkable for tackifier A as compared to tackifier B. An increase of the glass transition temperature was never observed for tackifier C. The peel adhesion was in the order of tackifier A > B > C. It was found that the compatibility of tackifier and base polymer had strong effect on adhesion properties.

Microstructures and Properties of High-strength Alloys Severely Deformed by Machining

Microstructures and properties were examined on the chip specimens severely deformed to a given shear strain (y) by machining in the high-strength Ni-base Inconel X-750 alloy and 6061-T6 aluminum alloy. Chip specimens has a deformation structure principally composed of elongated grains (for example, a few μm to about 100 μm in length and about 1 μm to a few tens μm in width for the chip specimen of γ≈3 of the Inconel X-750 alloy). Many subgrains separated by small or medium angle grain boundaries (misorientation, 0<15°) were also observed within relatively large grains. In the case where detailed analysis by FESEM/EBSP was possible, the fraction of large angle grain boundaries (θ≥15°) and that of medium angle grain boundaries (5°<0<15°) were relatively small, and most of grain boundaries were small grain boundaries (1°≤θ<5°) in the chip specimens of both alloys. Internal friction of the chip specimen was much larger than that of the original material. Large internal friction of the chip specimens was principally attributed to many cracks formed during machining. The hardness of chip specimens largely increased with increasing shear strain imposed by machining in the Inconel X-750 alloy, although the increase of hardness with shear strain was not so large in the 6061-T6 alloy.

Output Voltage Characteristics of Eddy Current Displacement Sensor for Various Heat Treatments of Measuring Objects

The output voltage of an eddy current displacement sensor (EC displacement sensor) depends on the heat treatment of the measuring object. The EC displacement sensor must detect a displacement of several tens of μm to allow the examination of the change in output voltage due to the heat treatment of the measuring object. Thus, we measure the relative permeability and resistivity of four objects made of chromium molybdenum steel that have undergone different heat treatments (initial condition (INT), salt quenching (SAQ), annealing (ANL), and vacuum furnace cooling (VFC)). In addition, we examine the relationship between the heat treatment of the measuring objects and the output voltage characteristics of the sensor at a displacement between the measuring object and the sensor of 1 mm. The result shows that the relative permeability of measuring object varies between 35 and 80, and resistivity varies between 0.18 μΩm and 0.35 μΩm due to different heat treatment conditions. The sensitivities of the sensor after SAQ and VFC treatments of the measuring object are 82.0 V/m and 73.0 V/m, respectively; thus, the difference is -11%.

Spectral properties of edge-emitting semiconductor laser subject to optical feedback from extremely short external cavity

We experimentally and theoretically study the impact of optical feedback from an extremely short external cavity (tens of μm) on the spectral behavior of edge emitting lasers (EELs). We are able to investigate a broad range of external cavity lengths and feedback strengths, by using a nanometer precision movable mirror attached to a fiber facet. A discrete modulation of the wavelength of operation is observed and its amplitude depends on the external cavity length and the external mirror reflectivity. We show that it is possible to optimize the tuning range of such a discrete wavelength tunable laser with respect to the external cavity and laser parameters.

Quantum Beam Studies on Polymer Crystallization under Flow

One of the longstanding issues in polymer science is crystallization of polymers under flow, especially formation of the so-called shish-kebab. Recent progress in quantum beam technology shed light on the substantial nature in the shish-kebab formation. In this paper we review our recent experiments on polymer crystallization under flow using time-resolved depolarized light scattering, small-angle and wide-angle X-ray scattering and small-angle neutron scattering in a wide spatial scale from 0.1 nm to several tens μm. These studies revealed that the shish-kebab formation is governed by a competition between the crystallization rate and the chain relaxation rate. Small-angle neutron scattering study on an elongated blend of deuterated low molecular weight and protonated ultra-high molecular weight polyethylenes showed that a long cylindrical object 2 μm in diameter and 12 μm in length was formed from deformed network of ultra-high molecular weight chains, which included three shishs (or extended chain crystals) 9 nm in diameter.

Morphology and Viscoelastic Properties of Poly(Vinyl Chloride)/ Poly(Vinyl Alcohol) Incompatible Blends

The effects of the pre-mixing method and degree of saponification poly(vinyl alcohol) (PVA) on the morphology of poly(vinyl chloride) (PVC)/PVA blends were investigated. Two pre-mixing methods were employed: a powder method and an aqueous solution method. In the powder method, both components were blended in powder form before melt kneading using a mixing roll. In the aqueous solution method, the PVC powder was added to an as-prepared PVA aqueous solution, followed by drying and then pounding before melt kneading. In the case of PVA with a degree of saponification of 98 mol%, PVA domains several hundred μm across were dispersed in the PVC matrix in the powder method system, whereas finer PVA domains with sizes ranging from sub μm to several μm were observed in the aqueous solution method. In the cases of PVA with saponification degrees of 88 and 78 mol%, domain sizes of several tens of μm were observed for both powder and solution methods. This indicates that there was no apparent influence of pre-mixing method on the domain size. When poly(methyl methacrylate) (PMMA) was added to the PVC/PVA blend, smaller PVA domains (with sizes ranging from 5 to 10 μm) were observed in both powder and solution method systems than without the PMMA. Viscoelastic properties showed specific interactions between PVC and PMMA, and between PMMA and PVA.

Diamond-like carbon for MEMS

Sputter-deposited amorphous diamond-like carbon (DLC, a-C) on silicon has been investigated with respect to micro electro mechanical systems (MEMS) applications. Sputtered a-C with a content of diamond-like sp3 bonded carbon of around 25% showed a high hardness of up to 30 GPa. Self-supporting cantilevers of 0.5 µm in thickness, several hundreds of µm in length and some tens of µm in width have been successfully realized using lift-off patterning of DLC and anisotropic silicon etching. The mechanical properties of DLC (Young's modulus, stress, stress gradient fracture strength) were characterized by cantilever deflection analyses. DLC strain gauge resistors integrated on micromachined silicon boss membranes were investigated under tensile and compressive loading. Piezoresistive gauge factors in the range of 20–30 were observed at temperatures between room temperature and 50 °C.

Surface composition of the largest dwarf planet 136199 Eris (2003 UB${_{313}}$)

Aims. The surface composition of the largest TNO, the dwarf planet 136199 Eris, is studied and compared to Pluto’s. Methods. High signal-to-noise visible and near-infrared reflectance spectra were obtained at the TNG and ESO-VLT observatories. The nature and properties of the compounds present on the surface of Eris are investigated by applying Hapke and Shkuratov radiative transfer models to our spectra. Results. The surface of Eris can be modeled using two areas of distinct composition: about 50% appears to be covered with pure methane ice, while the rest of its surface would be made of an intimate mixture of methane, nitrogen and water ices, and ice tholin. The use of nitrogen in our model is shown to improve significantly the data fit, in particular for high surface albedo values. The icy grains are found to be large, from sub-mm to a few tens of mm in size.

Direct synthesis of an anatase-TiO2nanofiber/nanoparticle composite powder from natural rutile

A new, environmentally friendly route to obtain an anatase TiO2 nanopowder from natural rutile sand is reported. The powder has been prepared via the direct hydrothermal process from natural rutile, followed by an ion-exchanging with HCl (aq). The new TiO2 powder possessed unique morphology, i.e., it was composed of anatase nanofibers (one to several tens μm in length and 10–50 nm in diameter) and anatase nanoparticles (about 10 nm in diameter). The direct hydrothermal process acted not only as a reaction step but also as a semi-purification step (from 96%-TiO2 in natural source to 99%-TiO2 in final product). This new direct hydrothermal process can be an industrial process to prepare low-cost TiO2 chemicals from natural source. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Imaging the Impact of Cortical Microcirculation on Synaptic Structure and Sensory-Evoked Hemodynamic Responses In Vivo

In vivo two-photon microscopy was used to image in real time dendrites and their spines in a mouse photothrombotic stroke model that reduced somatosensory cortex blood flow in discrete regions of cortical functional maps. This approach allowed us to define relationships between blood flow, cortical structure, and function on scales not previously achieved with macroscopic imaging techniques. Acute ischemic damage to dendrites was triggered within 30 min when blood flow over >0.2 mm2 of cortical surface was blocked. Rapid damage was not attributed to a subset of clotted or even leaking vessels (extravasation) alone. Assessment of stroke borders revealed a remarkably sharp transition between intact and damaged synaptic circuitry that occurred over tens of μm and was defined by a transition between flowing and blocked vessels. Although dendritic spines were normally ~13 μm from small flowing vessels, we show that intact dendritic structure can be maintained (in areas without flowing vessels) by blood flow from vessels that are on average 80 μm away. Functional imaging of intrinsic optical signals associated with activity-evoked hemodynamic responses in somatosensory cortex indicated that sensory-induced changes in signal were blocked in areas with damaged dendrites, but were present ~400 μm away from the border of dendritic damage. These results define the range of influence that blood flow can have on local cortical fine structure and function, as well as to demonstrate that peri-infarct tissues can be functional within the first few hours after stroke and well positioned to aid in poststroke recovery.

Tensile-strained Si layers grown on Si0.6Ge0.4 and Si0.5Ge0.5 virtual substrates: I. Film thickness and morphology

We have studied the structural properties of tensile-strained Si layers grown on polished Si0.6Ge0.4 and Si0.5Ge0.5 virtual substrates as a function of their thickness. Two gaseous precursor chemistries have been assessed for the reduced pressure–chemical vapour deposition of the sSi layers: SiH2Cl2 at 700 °C and SiH4 at 600 °C. We have used specular x-ray reflectivity and spectroscopic ellipsometry to gain access to the sSi layer thickness (and the associated sSi growth rate). The surfaces of sSi layers grown at 600 °C using SiH4 are characterized by a small spatial wavelength (a few hundred nm) roughness. Meanwhile, some lines along the ⟨1 1 0⟩ directions can be observed for thick sSi layers grown at 700 °C using SiH2Cl2, hinting at the presence of stacking faults. We obtained (for 10 µm × 10 µm atomic force microscopy images) surface root-mean-square roughness (Z ranges) between 0.19 and 0.36 nm (1.8 and 3.9 nm). By comparison, the rms roughnesses (the Z range) associated with 360 µm × 368 µm optical interferometry images are between 0.7 and 1.4 nm (7.1 and 12.1 nm), with some small amplitude but very long spatial wavelength (tens of µm) surface cross-hatch remaining on Si0.6Ge0.4 VS. The interfaces between sSi and SiGe are very abrupt, as illustrated by high-resolution transmission electron microscopy and by the Ge decay profile in secondary ions mass spectrometry: 0.73 nm/decade for sSi on Si0.5Ge0.5 VS and 1.06 nm/decade for sSi on Si0.6Ge0.4 VS, more or less independently of the sSi growth chemistry. The larger value for sSi on Si0.6Ge0.4 VS is most probably due to some instrumental broadening linked to the small remaining cross-hatch.

Affinity and Kinetic Analysis of Fcγ Receptor IIIa (CD16a) Binding to IgG Ligands

Binding of pathogen-bound immunoglobulin G (IgG) to cell surface Fc gamma receptors (FcgammaRs) triggers a wide variety of effector functions. The binding kinetics and affinities of IgG-FcgammaR interactions are hence important parameters for understanding FcgammaR-mediated immune functions. We have measured the kinetic rates and equilibrium dissociation constants of IgG binding to a soluble FcgammaRIIIa fused with Ig Fc (sCD16a) using the surface plasmon resonance technique. sCD16a interacted with monomeric human IgG and its subtypes IgG1 and IgG3 as well as rabbit IgG with on-rates of 6.5 x 10(3), 8.2 x 10(3), 1.1 x 10(4) and 1.8 x 10(4) m(-1) s(-1), off-rates of 4.7 x 10(-3), 5.7 x 10(-3), 5.9 x 10(-3), and 1.9 x 10(-2) s(-1), and equilibrium dissociation constants of 0.72, 0.71, 0.56, and 1.1 mum, respectively. The kinetics and affinities measured by surface plasmon resonance agreed with those obtained from real time flow cytometry and competition inhibition binding experiments using cell surface CD16a. These data add to our understanding of IgG-FcgammaR interactions.

One-dimensional gallium nitride micro/nanostructures synthesized by a space-confined growth technique

Hexagonal GaN prismatic sub-micro rods and cone nanowires have been synthesized in a large scale by a novel and controllable space-confined growth method. The as-synthesized GaN products are highly crystalline with a wurtzite structure. The prismatic rods have lengths of 15∼20 μm and diameters of 400∼500 nm enclosed by hexagonal smooth side surfaces and a pyramidal end. And the cone nanowires have average diameters of 150∼200 nm and lengths up to several tens of μm with a cone tip. The photoluminescence (PL) studies reveal prominent band-gap UV emission properties of GaN products and narrow FWHM, indicating the excellent luminescent performance and high crystal quality. For field emission characteristic of GaN nanowires, the turn-on field is about 9.5 V/μm and the current density reaches 1.0 mA/cm2 at an electric field of 18 V/ μm. The contrast experiments indicate a novel growth control can be achieved by using a graphite tube as reaction vessel. The sealed graphite tube combined with metallic initiator is greatly responsible for large-scale and uniform preparation of GaN prismatic rods and cone nanowires. Highly symmetric GaN hexagonal micropyramids are grown on a bare Si substrate. The growth mechanism and the control function of the graphite tube are demonstrated. These low-dimensional structures not only enrich semiconducting GaN family, but also are good building blocks for optoelectronic devices.

Phase separation and dewetting in polymer blend thin films

We have studied morphology and kinetics of phase separation and dewetting in thin films of polystyrene and poly(vinyl methyl ether) blend on glass substrate using light scattering (LS) and optical microscope (OM) techniques as well as using atomic force microscopy (AFM). As the film thickness decreases from several tens μm, a peak in LS profiles characteristic to phase separation once disappears at the film thickness of ∼1μm, which corresponds to the characteristic wavelength of phase separation. Below this film thickness, we found dewetting is triggered in addition to the phase separation. In thin films below about 100 nm a scattering peak is again observed, which has been assigned to the characteristic wavelength of the dewetting. The results are discussed in terms of the characteristic wavelength of phase separation in relation to the film thickness.

Gas Electron Multipliers for Potential Applications to Digital Radiography

The gas electron multiplier (GEM), placed in the drift volume of a conventional gas detector, is a conceptually simple device for producing a large gas gain by concentrating the drift electric field over a very short distance to the point that electron avalanching occurs. This device consists of a thin insulating foil of several tens of μm in thickness, covered on each side with a thin metal layer, with tiny holes, usually 100 μm or less in diameter, and with a spacing of 100-200 μm through the entire foil, perforated by using chemical etching or high-powered laser beam technique. In this study, we have investigated its operating properties with various experimental conditions and demonstrated the possibility of using this device as a digital X-ray imaging sensor, by acquiring X-ray images based upon the scintillation lights of the GEM with a standard CCD camera.