Crystal face dependent chemical effects in surface-enhanced Raman scattering at atomically defined gold facets

Among electromagnetic and chemical (CM) contributions to surface-enhanced Raman scattering (SERS), the former is becoming controllable according to the recent progress in nanofabrication of plasmonic metal structures. However, it is still difficult to control the latter effect. Here, the degree of each contribution to SERS signals is examined on well-defined single crystalline facets of gold by using optical field localization within sphere-plane type plasmonic cavities. Crystal face dependent SERS studies of aminobenzenthiol adsorbates clearly show the distinction between CM enhancements on different surfaces, suggesting that the CM-activity of "SERS-hotspots" is closely related to interfacial dipoles formed at metal-molecular junctions.     

Contribution of Ti addition to characteristics of extruded Cu40Zn brass alloy prepared by powder metallurgy

The aim of this paper was to investigate the properties of Cu40ZnTi for the purpose of developing a new high-strength, lead-free brass by powder metallurgy. The effect of Ti addition on precipitation hardening behavior of Cu40Zn (denoted as BS40) brass was studied with respect to mechanical properties and microstructures. BS40 and Cu40Zn − 1.0 wt.%Ti (denoted as BS40-A) brass powders were prepared by water atomization process, and β phase was retained in the raw powders predominately. The BS40 powder and Ti powder were elementally mixed to prepare Cu40Zn + 0.5 wt.%Ti (denoted as BS40-B) and Cu40Zn + 1.0 wt.%Ti (denoted as BS40-C) premixed powders. The alloy powders and premixed powders were solidified at 1053 K for 600 s by spark plasma sintering (SPS) and extruded subsequently. It was observed that Cu₂ZnTi intermetallic compound (IMC) and CuZnTi metastable phase resulted from the reaction between Ti and CuZn showed distinct grain refinement effect on extruded Cu40Zn brass. Thus, the excellent strengthening effect processes by precipitation hardening and deform working was obtained, which responding to an yield strength of 345 MPa, and a ultimate tensile strength of 597 MPa, showed 65.9% and 30.4% higher than that of extruded Cu40Zn brass, respectively.     

Fabrication and properties of lead-free machinable brass with Ti additive by powder metallurgy

The aim of this paper was to investigate the properties of Cu40Zn2.2Bi + Ti for the development of a new lead-free, high-strength and machinable brass by powder metallurgy. The effect of Ti addition on the mechanical properties and machinability of BS40-2.2Bi (Cu40Zn2.2Bi) brass was studied with respect to different contents of Ti addition. BS40 (Cu40Zn) and BS40-2.2Bi brass powders were prepared by water atomization process, and the β phase was retained in the raw powders predominately. The BS40-2.2Bi powder and Ti powder were elementally mixed to prepare BS40-2.2Bi + xTi (x = 0.3, 0.5 and 1.0 wt.%) premixed powders. The alloy powders and premixed powders were solidified at 1053 K for 600 s by spark plasma sintering (SPS) and extruded subsequently. It was observed that intermetallic compounds (IMCs) such as Ti₂Bi were formed via the reaction between additive Ti and Bi alloying elements, and improved the ductility of BS40-2.2Bi significantly. The yield strength (YS) and ultimate tensile strength (UTS) were increased by increasing the contents of Ti addition, however, the elongation showed a decrease trend and the machinability became worse. The optimal content of Ti addition was 0.3 wt.%, which served excellent mechanical properties and machinability comparing with BS40-2.2Bi. For example, it had a YS of 235 MPa, a UTS of 459 MPa and an elongation of 39%, which showed 4.9%, 4.1% and 18% higher than that of extruded BS40-2.2Bi brass, respectively.     

Effect of stereoregularity and molecular weight on the mechanical properties of poly(vinyl alcohol) hydrogel

The effect of the stereoregularity and molecular weight of poly(vinyl alcohol) (PVA) on the mechanical properties of hydrogel was investigated. Compressive strength, creep behavior, and dynamic viscoelasticity were measured on hydrogels of syndiotacticity‐rich PVA derived from poly(vinyl pivalate) (D_p = 1690 diad‐syndiotacticity = 61%, D_p = 8020 diad‐syndiotacticity = 62%) and atactic PVA (D_p = 1750 diad‐syndiotacticity = 54%, D_p = 7780 diad‐syndiotacticity = 54%). Increasing the molecular weight of molecular chains constituting the gel improved the compressive strength of atactic PVA hydrogel. The stereoregularity of PVA had a greater effect than molecular weight on the strength of the hydrogel. Gel prepared from 8.8 g/dL syndiotacticity‐rich PVA had a high compressive modulus of 10 kPa, and the compressive modulus of the gel prepared from 3.3 g/dL was comparable with that of atactic PVA hydrogel prepared with more than 6 g/dL. The dynamic storage modulus of the gel derived from syndiotacticity‐rich PVA was remarkably higher than that of the atactic PVA gel and remained constant up to 60°C. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Development of a System for Location Finding of Low-Level Sound Source by Using Human Acoustic System with Stochastic Resonance

The purpose of this study is to develop a system that enables location finding of a small sound. The location finding of a small sound has some difficulties such as high computational costs or disturbances from the ambient noises and reflected waves. The proposed system is composed of a biologically-inspired system which uses a hearing mechanism based on the human ear and a mechanism for perceiving weak signals that uses stochastic resonance. The location finding mechanism in the proposed system is based on the time-lag detecting architecture. On the other hand, the stochastic resonance mechanism can pick up the small sound source in the ambient noises. Using this proposed system, we implemented the location finding of small sounds through numerical simulations and hardware experiments. Good results were obtained for the small sound source location finding.     

Fabrication process of intrinsic Josephson junction stacks in Bi2Sr2CaCu2O8+x crystals by double-sided patterning process using dilute hydrochloric acid

We have developed a new double-sided patterning (DSP) process that employs dilute acid (pH = 1.65) to fabricate Bi₂Sr₂CaCu₂O_8+x (Bi-2212) stacks of intrinsic Josephson junctions. These stacks, which were fabricated from a single crystal of Bi-2212, were surrounded by an acid-treated product. The critical aspect of this process is that the Bi-2212 surrounding the photoresist pattern was converted into a transparent material, BiOCl, which was connected with the Bi-2212 crystal. Consequently, this process provides a simple way to achieve DSP of the surfaces of Bi-2212 crystals. This new DSP process realizes a remarkably improved reproducibility in fabricating Bi-2212 stacks that exhibit good current–voltage characteristics with a large hysteresis and multiple branches at T = 77 K.     

The combinational or selective usage of the laser SQUID microscope,the non-bias laser terahertz emission microscope,and fault simulations in non-electrical-contact fault localization

Recently, in the field of fault localization of LSI chips, several non-electrical contact techniques have been proposed. The techniques include the laser SQUID microscope (L-SQ) and the non-bias laser terahertz emission microscope (NB-LTEM). Both techniques have pros and cons. The L-SQ, for examples, can localize open defects in some cases, but it requires closed circuit. The NB-LTEM can localize open defects and short defects, and not requires closed circuit. The NB-LTEM, however, cannot localize open defects in some cases. The fault simulation specially designed for the L-SQ or the NB-LTEM makes it precise or efficient to localize defects. The combinational or selective usage of the L-SQ, the NB-LTEM and the related simulations makes it possible to localize defects in many cases. In this paper, we would like to review our results and organize them from the viewpoint of failure mode and defect sites.     

Laser THz emission microscope as a novel tool for LSI failure analysis

We have proposed and developed a novel technique for a non-contact inspection of defective interconnections in an LSI chip using a laser terahertz emission microscope (LTEM). The LTEM measures the THz emission images of an LSI chip by scanning it with fs laser pulses. When a fs laser pulse irradiates a p–n junction in an LSI chip, transient photocurrent flows into interconnections resulting in the emission of the THz pulse into free space. We investigated the characteristics of the THz emissions from simple test element group samples which consist of p–n junctions connected to metal lines. It was found that the metallic lines connected to photo-excited p–n junctions worked as THz emission antennae which enhance the emission efficiency of THz pulses near their resonant frequencies corresponding to the line lengths. This result indicates that THz emission signals from p–n junctions in circuits strongly depend on the structure of the interconnections. We show the successful results on the inspection of defective interconnections in MOSFET devices and C7552 ISCAS’85 benchmark circuits using LTEM. By comparing the THz emission images between a normal circuit and a defective one, it is possible to identify the p–n junctions connected to the defective interconnections without electrical contacts.