Interaction of π-bonds of the silicon–silicon triple bond with alkali metals: An isolable anion radical upon reduction of a disilyne

The reduction of 1,1,4,4-tetrakis[bis(trimethylsilyl)methyl]-1,4-diisopropyltetrasila-2-yne 1 with an equivalent amount of alkali metal (Li, Na, K, KC₈) in THF produced the corresponding disilyne anion radicals 2a–c. Their EPR spectra are independent of the metals used in THF, indicating that the disilyne anion radical species exists as solvent-separated ion pairs in polar solvents. The one-electron reduction also occurred with potassium in toluene to produce the potassium salt of the anion radical 3, which was isolated as extremely air- and moisture-sensitive dark brown crystals. The molecular structure of 3 was established by X-ray crystallography, which showed that the potassium ion is solvated by one toluene molecule. The EPR spectrum of 3 in toluene showed the interaction of the anionic silicon atom with the K⁺ ion.     

Control of carbon incorporation in AlAs grown by atomic layer epitaxy using variously orientated substrates

We demonstrate a method for successfully controlling carbon incorporation in AlAs layers grown by atomic layer epitaxy (ALE) using various GaAs substrates with different orientations. The number of alkyl radicals attached to an Al atom at the surface, which is a main factor in carbon incorporation, can be intentionally controlled by changing substrate orientation. We found that the carbon incorporation in ALE-AlAs using the (3 1 1)B surface is 2 x 10¹⁷,cm^-3, which is the lowest value ever reported for ALE-AlAs that satisfies one-monolayer self-limiting growth conditions.     

Up-to-date development of lithium-ion batteries in Japan

In this paper, the authors review the up-to-date development of lithium-ion batteries (LIBs), focusing mainly on the situation in Japan. The materials, constructions, and electrochemical performance of the latest commercially available LIBs, including lithium polymer batteries, which have come onto the market only fairly recently, are described in the first half of this article. The authors then discuss the recent trends in the development of battery materials for LIBs as well as those of large-scale LIBs     

Pb-free surface-finishing on electronic components’ terminals for Pb-free soldering assembly

Pb-free solderable surface finishing is essential to implement Pb-free solder assembly in order to meet with the growing demand of environmental consciousness to eliminate Pb from electronic products. Two types of widely applicable Pb-free surface finishing technologies are developed. One is the multilayer-system including Pd with Ni undercoat. Heat-resistance of Pd enables whole-surface-plating on to leadframe before IC-assembling process. The other is the double-layer-system with low-melting-point-materials, for example, thicker Sn underlayer and thinner Sn-Bi alloy overlayer, dilutes Sn-Bi alloy’s defects of harmful reactivity along with substrate metal and mechanical brittleness with keeping its advantages of solder-wettability and no whisker.     

SAW velocity measurement of crystals and thin films by the phasevelocity scanning of interference fringes

We present principle and application of a novel noncontact velocity measurement of surface acoustic waves (SAW) on crystals and thin films using laser interference fringes scanned at the phase velocity of SAW. The scanning interference fringes (SIF) are produced by intersecting two laser beams with a frequency difference. The SAW velocity within the laser beam spot is measured as the ratio of observed SAW frequency and predetermined wave number of the SIF. The frequency measurement can be quite precise because of a large number of generated SAW carriers and amplitude enhancement effect. The SAW velocity measurement is free from the water loading effect accompanying the leaky SAW measurements. This principle was successfully applied to evaluate Si ₃N₄ and SiO₂ films deposited on Si (001) surface     

Experimental verification of image detection in highly scattering media using antenna properties of optical heterodyne microscope scheme

The spatial resolution capability for image detection in the presence of strong scattering inside a medium is verified by virtue of the antenna properties of the optical heterodyne method. The image formation of test microletters in a highly scattering solution is successfully achieved using an optical heterodyne scanning microscope.<>     

An Information-Based Elite-Guided Evolutionary Algorithm for Multi-Objective Feature Selection

<正>Dear Editor, This letter is concerned with the evolution strategy for addressing multi-objective feature selection problems in classification. Previous methods suffer from limitations such as being trapped in local optima and lacking stability. To overcome them, we propose a novel eliteguided mechanism based on information theory. Firstly, an elite solution is generated through a dimension reduction strategy and incorporated to the initialization population. Then,     

Comparison of the SiH4---C2H4 and SiH2Cl2---C2H4 systems during the synthesis of silicon carbide ultrafine particles by laser-induced gas-phase reaction

The synthesis conditions of SiC ultrafine particles from SiH₄ and C₂H₄ using a CO₂ laser were studied and a comparison was made between SiH₄---C₂H₄ and SiH₂Cl₂---C₂H₄ systems. Ultrafine SiC particles were synthesized by irradiating a SiH₄ and C₂H₄ gas mixture with a CO₂ laser at atmospheric pressure. SiC particles were obtained at a laser power of more than 0·92 kW/cm².

The behavior of the reaction flame temperature and the extent of the laser light absorption by SiH₄---C₂H₄ was different from that of SiH₂Cl₂---C₂H₄, although an abrupt temperature increase was observed in both cases. In the case of SiH₄---C₂H₄ an abrupt increase in the laser light absorption was not observed, whilst it was observed in the case of SiH₂Cl₂---C₂H₄. This difference resulted from the difference in liability to form solid carbon particles.     

Elastic properties measurement of glass layers fabricated onsilicon wafers for microelectronics and micromachines

Elastic properties such as the Young's modulus, the Poisson's ratio and the density of Si-B-O glass layers fabricated on (100) silicon substrates by the flame hydrolysis deposition method were measured. Thicknesses of the layers were about 20 μm. It was found that the Young's modulus decreased with the boron dopant concentration. The Poisson's ratio was about 0.26 regardless of the boron dopant concentration. The measured elastic properties will be used in the design of micromachines fabricated with silicon substrates and glass layers