Yasuo Hirabayashi

Micro Press Molding of Borosilicate Glass Using Plated Ni–W Molds

The hot embossing of glass with a size on the submicron or micron level is a target of interest for the industrial production of products such as microdevices. For fluidic micro chip applications, polymer materials have been used with the advantage of a relatively low cost of fabrication. However, glass is suitable for high-temperature applications such as in microreactors. Although glass is also a good candidate material for optical devices because of its enhanced optical properties, the development of mold materials has not been established for the hot embossing of glass. In this study, we used Ni–W as a mold material for the hot embossing of glass. A plated Ni–W film has a high heat resistance and a linear expansion coefficient, properties that are similar to those of glass materials. Focused ion beam (FIB) machining was employed for the micron and submicron structurings of a Ni–W mold material. Borosilicate glass, D263, was used as glass material. Glass patterns of 0.4 µm width were obtained by hot embossing with the Ni–W mold.

Magnetically actuated micromirror and measurement system for motion characteristics using specular reflection

Micromachined magnetically actuated torsional micromirrors have been fabricated. The micromirrors based on silicon were actuated by moving magnet system using hard magnetic (Co-Pt) or soft magnetic (Fe-Ni) thin films. And a system to measure motion characteristics of the micromirrors was assembled with an optical table, optical mounts, and optics. The system is based on a specular reflection of He-Ne laser from the micromirrors. We measured static and resonance characteristics of the micromirrors with Co-Pt film or Fe-Ni film. Then we measured Q factors of the micromirrors; with Co-Pt film in vacuum. Using our system for measurements, we obtained motion characteristics of micromirrors at large angular deflections. Measured resonance characteristics of all micromirrors are in good agreement with the equation of forced vibration with viscous damping. Micromirrors with Co-Pt films have better reproducibility of torsional motions than ones with Fe-Ni films in both dc magnetic field and ac magnetic field. And micromirrors with Fe-Ni films have torsional motion with subpeak at resonance characteristics. The Co-Pt film is more useful as a magnetic film for the micromirror than the Fe-Ni film at static and resonance characteristics.

High performance of hydrogen peroxide detection using Pt nanoparticles-dispersed carbon electrode prepared by pulsed arc plasma deposition

We propose novel electrodes with platinum nanoparticles dispersed on a glassy carbon (Pt-NPs/GC) prepared using a pulsed arc plasma deposition (APD) method. The method could coat Pt-NPs on a base material directly with a single-step process in a very short deposition time. The characteristics of the electrodes were discussed in detail. The detection of hydrogen peroxide was performed as an example for application of the electrodes. The distribution of nanoparticles was controlled easily by the number of pulse. The surface morphology changed with the pulse number and the annealing except for the sample prepared by 5 pulses deposition (APD(5)), implying that the APD(5) remained as NPs after the annealing. Average particle size was 2.7 nm on the Pt-NPs/GC. Catalyst activity for oxidizing hydrogen peroxide per Pt loading was excellent on the Pt-NPs/GC. When the Pt-NPs/GC was used as a detector for hydrogen peroxide on a flow injection analysis, the Pt-NPs/GC showed high sensitivity without deterioration. Oxidation current increased linearly with the concentration of hydrogen peroxide from 10nM to 100 μM. This fast and easily prepared electrode showed the capability to replace a conventional bulk metal electrode.

Structural modulation on multilayered bismuth cuprate observed by x-ray reciprocal space mapping

Epitaxial Bi2Sr2Ca1Cu2Ox(Bi-2212)∕Bi2Sr2Cu1Ox(Bi-2201) multilayer was investigated by x-ray diffraction methods in order to investigate the effect of internal strain on structural modulation. In multilayered structure, the effect of internal strain is more prominent than in an aliovalent substitution, such as a substitution of La3+ for Sr2+. X-ray reciprocal space mapping (XRSM) was taken on the ω-2θ plane (cross-section XRSM) in order to estimate the lattice constants along the in-plane and out-of-plane directions, and θ-2θ scan was used to verify the multilayered structure. Another XRSM method, plan-view XRSM, was employed to verify the in-plane symmetry of structural modulation on the ω-ψ plane. The structural modulation was observed on both the cross-section and plan-view XRSM. The lattice constants together with the modulation vector in multilayer were varied by the multilayer periods without any substitution in the original structure.

Optimizing coverage of metal oxide nanoparticle prepared by pulsed laser deposition on nonenzymatic glucose detection.

Metal oxide nanoparticles prepared by pulsed laser deposition (PLD) were applied to nonenzymatic glucose detection. NiO nanoparticles with size of 3 nm were deposited on glassy carbon (GC) and silicon substrates at room temperature in an oxygen atmosphere. Transmission electron microscope (TEM) image showed nanoparticles with the size of 3 nm uniformly scattered on the Si(001) substrate. Unlike co-sputtering nanoparticle and carbon simultaneously, the PLD method can easily control the surface coverage of nanoparticles on the surface of substrate by deposition time. Cyclic voltammetry was performed on the samples deposited on the GC substrates for electrochemical detection of glucose. The differences between peak currents with and without glucose was used to optimize the coverage of nanoparticles on carbon electrode. The results indicated that optimal coverage of nanoparticles on carbon electrode.

Large constriction of lattice constant in epitaxial magnesium oxide thin film: Effect of point defects on lattice constant

Epitaxial thin films prepared using an MgO target on silicon substrate often show constriction of lattice constant (a∼4.1 A). Detailed investigation of the crystal structure excluded the possibility that the epitaxial films are either cubic spinel MgO or magnesium silicate (a/2∼4.1 A). With such a constriction in rock salt MgO structure point defects must be induced into structure. An ab initio method with semicore pseudopotentials predicted such constrictions on configurations of Schottky type defects. The Schottky defects with random distribution throughout lattice cites satisfied constricted lattice constant, mass density, and crystallography experimentally observed on the epitaxial MgO films.

C-Axis lattice spacing control of As-grown Bi-Sr-Ca-Cu-O thin films by single-target excimer laser ablation

As-grown c-axis-oriented thin films of Bi-Sr-Ca-Cu-O on MgO(100) substrates were prepared by simultaneous deposition using the pulsed excimer laser ablation technique. The c-axis spacing of lattice planes could be controlled by the variation of Ca and Cu contents using simultaneous deposition with single targets. As Ca and Cu contents increased, the peaks of the X-ray diffraction pattern approached that of (Ca0.86Sr0.14)CuO2; the n=∞ parent of the Bi2Sr2Can-1CunOy superconductors with a lattice constant, 3.1995 A, of the c-axis. After postannealing, films with Tc,end over 100 K were obtained.

Nano-strip grating lines self-organized by a high speed scanning CW laser.

After a laser annealing experiment on Si wafer, we found an asymmetric sheet resistance on the surface of the wafer. Periodic nano-strip grating lines (nano-SGLs) were self-organized along the trace of one-time scanning of the continuous wave (CW) laser. Depending on laser power, the nano-trench formed with a period ranging from 500 to 800 nm with a flat trough between trench structures. This simple method of combining the scanning laser with high scanning speed of 300 m min(-1) promises a large area of nanostructure fabrication with a high output. As a demonstration of the versatile method, concentric circles were drawn on silicon substrate rotated by a personal computer (PC) cooling fan. Even with such a simple system, the nano-SGL showed iridescence from the concentric circles.

Twin-Free Epitaxial Films Lateral Relation between YSZ(111) and Si(111)

Yttria-stabilized zirconia (YSZ) films were prepared on Si(111) substrates with a slow deposition rate. X-ray diffraction clearly showed epitaxial growth of YSZ(111) film on Si(111), the X-ray scan of 3-fold symmetry confirmed single domain YSZ(111) to be rotated 180° about the surface normal from cubic on cubic relation. In contrast, single domain Si(111) films showed cubic on cubic relation with the YSZ(111) substrate.

Numerical Simulation of Glass Imprinting for Molding Temperature Prediction

For optimizing the conditions of glass imprinting, many researchers commonly use the trial-and-error method. Therefore, it is advantageous to carry out a preliminary analysis of glass imprinting. The viscoelastic property of glass is necessary for MEMS-ONE in which a viscoelastic model is used. Assuming glass materials to be viscoelastic boies, the relaxation share modulus was measured by the creep test based on traditional thermo-viscoelastic theory. The Williams–Landel–Ferry (WLF) equation is applied using the temperature dependence of liquid viscosity. We compared experimental results with the analytic results of MEMS-ONE simulation under the conditions of fixed pressure (3.56 MPa) and time (10 min). The object of evaluation is the height of the central position prong. The molding temperature can be predicted within 10 °C error by the simulation.