Assembling 100 nm Scale Particles by an Electrostatic Potential Field

The assembly of particles is one of the many methods for the fabrication of organized structures in the range of micro- to nanometer sizes. These structures have potential applications in the electronic, optical and biochemical fields. Recently, many papers have reported the patterning of particles using patterned SAM (self-assembly monolayer) films and micro molding methods. We have been developing a new technique to assemble particles using an electrostatic field. This paper describes a new technique to fabricate two-dimensional microstructures assembled from 100 nm particles. Spherical silica of 900 nm diameter and aluminum of 100 nm diameter were used as the model particles. An electrostatic image was formed on an insulating substrate by drawing a focused electron beam at 10 keV. Both types of particles were deposited on the electrostatic images. In this process, the dielectrophoretic (DEP) force plays an important role in depositing particles on the electrostatic images. The DEP forces for particles in a suspension were calculated using numerical analysis. The result showed that the DEP force above the electrified region on the substrate is larger than disturbing forces, such as Brownian motion.     

Phase behaviour and molecular dynamics in the binary system of sodium perchlorate and 1,2-propanediamine

The phase and glass transition behaviour in a binary mixture of sodium perchlorate and 1,2-propanediamine {(NaClO₄)_x(12PDA)_1?x, x < 0.40} was investigated by differential scanning calorimetry and Raman scattering measurements. A eutectic point and a peritectic point were found at x = 0.17 and 0.19, respectively. The phase diagram indicates the existence of solvated compounds of (NaClO₄)₁(12PDA)₄ and (NaClO₄)₂(12PDA)₅. The concentration dependence of the glass transition point shows a sigmoid curve implying an underlying anomaly.     

Far-infrared spectroscopy by synchrotron radiation at the UVSOR Facility

At the UVSOR Facility, Institute for Molecular Science, the practical use of the synchrotron radiation as a far-infrared light source has started. A spectroscopic system has been constructed at the beam line BL6A1 of UVSOR storage ring, which covers the wavenumber region from 5 to 250 cm^–1. The cross sectional diameter of the light beam at the sample position is as small as 3 mm with the angular divergence of about 100 mrad. The system has been made mainly for the transmission and reflection measurements of small samples with small angular divergence by the use of the high brightness of the synchrotron radiation. Examples of observed transmission and reflectivity spectra are shown.     

Excess resistance in the superconducting transition of a mesoscopic Al disk

We report resistance measurements on a mesoscopic Al disk whose size is comparable to the superconducting coherence length. As the magnetic field increases, resistance peaks successively appear and some of the peak resistances are larger than the normal state value R_N. These peaks are ascribed to the transitions between different vortex states in the superconducting Al disk. The experimental results suggest that some anomalous energy dissipation is caused by the dynamics of the vortices in the confined geometry.     

Line-Mixing Calculations for the 5.3 μm NO Band

Line-mixing coefficients of the NO-N₂ system are calculated within the infinite-order sudden (IOS) and energy-corrected sudden (ECS) approximations. The so-called sum rule between the line width and the line-mixing coefficients is used for line-mixing calculation. Line widths calculated from the ECS model are in good agreement with experimental data for the 5.3 μm NO band. The band-correction function of NO, which characterizes the deviations from the superposition of Lorentz profiles, is also calculated. The ECS results as well as experimental data indicate strong sub-Lorentzian behavior in the wing of the R branch of the 5.3 μm NO band.     

Fabrication of carbon nanotube assemblies on Ni–Mo substrates mimics law of natural forest growth

We fabricated cone-shaped carbon nanotube assemblies, which align in a densely packed geometry like a cedar tree forest, on unpatterned nanocomposite substrate of Ni and Mo by the DC plasma assisted hot filament chemical vapor deposition. Carbon nanotubes initially grew on the nickel domains created during deposition, forming cone-shaped assemblies. These assemblies grew keeping their shape with decreasing their number density by merging together. The relationship between the mean volume and the number density of conical-shaped tree-like assemblies was similar to one of natural plant forest.     

Fluid-dynamic interaction between two spheres

Experiment of fluid-dynamic interaction between two spheres was conducted to obtain basic information concerning the two-phase flow, especially in dense phase. Two or three spheres were set up in a water tunnel in the longitudinal or transverse direction with Reynolds numbers less than 10³. The flow behind the sphere was visualized by the use of condense milk and change in vortex structure due to the interaction was observed in detail. Additionally, drag force on the sphere was measured by a pendulum method which was developed to detect small drag, and the range of distance in which the drag is affected by the interaction was shown.