Shinya Terauchi

Fabrication of Au nanoparticles by radio-frequency magnetron sputtering

Abstract We have investigated the evolution of the size and the morphology of Au nanoparticles fabricated by r.f. magnetron sputtering techniques at room temperature as a function of sputtering gas pressure, p; r.f. input power, L; and sputtering time, t. For 60 ≤ p ≤ 300 mTorr, Au nanoparticles were deposited. For 60 ≤ p ≤ 250 mTorr, the particle size increased with increasing L and extending t. On increasing L and t further, film formation occurred. When p = 300 mTorr, nanoparticles formed at L = 200 W.

Structure and Corrosion Behavior of Conversion Coatings on Magnesium Alloys

We studied various types of surface treatments for magnesium alloys that involved the application of chromium or manganese by measuring their corrosion potential using X-ray diffraction, X-ray photoelectron spectroscopy, auger electron spectroscopy, and microscopic examination. The chromium-conversion coating is composed primarily of amorphous trivalent chromium oxide (or hydroxide) and a fluoride of magnesium and aluminum. The permanganate-conversion coatings, we obtained by adding HF to the immersion bath, consisted of a film that was composed primarily of manganese oxides and magnesium fluoride, We found that these films formed an amorphous composite coating In addition, we examined the corrosion resistance of AZ91D magnesium alloy die-cast panels with various surface treatments. The exposure tests, we performed in Miyakojima, indicated that the anodic c oxidation coating and the MX1-type surface treatment containing chromate, which result in relatively thick coatings, are superior in corrosion resistance. The corrosion resistance of permanganate chemical conversion coatings is comparable with that of chromium conversion coatings.

Characterization of CoO-Doped SiO2 Nanocomposite Films and Their Optical Transmittance Change by Nitrogen Oxide

We developed CoO-doped nanocomposite films which change their optical transmittance by nitrogen oxide using co-sputtering method. Films sputtered from SiO2 target with CoO pellets on at 100W under 0.27 Pa Ar atmosphere showed reversible transmittance change by NO at 350°C in the wavelength range from 400 to 800 nm. Cobalt oxide dots 4-8 nm in diameter were observed in the CoO/SiO2 nanocomposite films by TEM observation. The heat-treated CoO/SiO2 film at 600°C which showed no transmittance change by NO still had cobalt oxide nanoparticles embedded in SiO2 matrix. The sensing properties is considered to be originated from nanostructure composed of functional nanoparticles which change their optical transmittance, nanopores which give paths of gas molecules and transparent matrix,

Nanostructure and chemical state of nanocomposites prepared by co-sputtering method

Abstract We prepared two types of nanocomposites by the co-sputtering method: (a) Si-dispersed in SiO 2 , Al 2 O 3 or MgO, and (b) MO x /SiO 2 , MO x /Al 2 O 3 (M: transition metal from Ti to Zn). The nanostructures and the chemical states of nanocomposite constituents were characterized by TEM and XPS, respectively. The relationship between the optical properties and the nanostructures were also studied. For Si-dispersed nanocomposites, photoluminescence increased during the disproportionation process of SiO x . Quantitative analysis of nanocomposite series, MO x /SiO 2 and MO x /Al 2 O 3 revealed that the concentration of dispersoid did not always agree with simple estimations from the sputtering yield and the area ratio.

Automatic coarse-alignment for TEM tilt series of rod-shaped specimens collected with a full angular range.

An automatic coarse-alignment method for a tilt series of rod-shaped specimen collected with a full angular range (from alpha=-90 degrees to +90 degrees, alpha is the tilt angle of the specimen) is presented; this method is based on a cross-correlation method and uses the outline of the specimen shape. Both the rotational angle of the tilt axis and translational value of each image can be detected in the images without the use of markers. This method is performed on the basis of the assumption that the images taken at alpha=-90 degrees and alpha=+90 degrees are symmetric about the tilt axis. In this study, a carbon rod on which gold particles have been deposited is used as a test specimen for the demonstration. This method can be used as an automatic coarse-alignment method prior to the application of a highly accurate alignment method because the alignment procedure can be performed automatically except for the initial setup of some parameters.

Synthesis of GaAs nanoparticles embedded in SiO2 matrix by radio frequency co-sputtering technique

Nanoparticles of GaAs embedded in SiO2 matrix were prepared by radio a frequency co-sputtering technique. The content of GaAs in the composite films was varied by varying the number of pieces of GaAs co-targets on a SiO2 target. The as-grown composite films were amorphous in nature. the optical absorption spectra of the films revealed a large shift in the optical band gap of GaAs, which partly corresponds to the strong quantum confinement of electrons and holes in the nanoparticles and is partly due to their amorphous nature.

Calibration method of tilt and azimuth angles for alignment of TEM tomographic tilt series

This paper describes the calibration method of the tilt and azimuth angles of specimen using a digital protractor and a laser autocollimator for alignment of electron tomography. It also suggests an easy method to check whether the specimen is tilted by 180.0°, and whether the azimuth angle is 0.0°; the method involves the use of two images of a rod-shaped specimen collected before and after a 180.0° tilt. The method is based on the assumption that these images are symmetric about the tilt axis when the azimuth angle is 0.0°. In addition, we used an experiment to demonstrate the effect of the incorrect angles on reconstructed images and simulated the image quality against distance away from tilt axis.

Interdiffusion studies for HfO2/Si by GIXR and XPS

Interdiffusion at the interface between an HfO2thin film and a Si substrate was studied using grazing incidence x-ray reflectivity (GIXR) and x-ray photoelectron spectroscopy (XPS). HfO2thin films were deposited on Si sub strates by the sputtering of a metal-Hf layer, and then they were oxidized/annealed in a N2/O2gas mixture with different O2concentrations. The GIXR and XPS results showed that the out-diffusion of Si atoms from the substrate increased with the oxygen concentration during high temperature annealing, and consequently, it resulted in the formation of a Si-rich Hf-silicate interlayer, i.e., lower-density Hf-silicate with greater thickness. The GIXR results of the interfacial structures were in agreement with the results of XPS and cross-sectional transmission electron microscopy.

Formation of Platinum and Palladium Bimetallic Superfine Particles by Ultrasonic Irradiation

Pt/Pd bimetallic nanoparticles were prepared by ultrasonic irradiation of aqueous solutions containing salts of both metal ions. Uniform bimetallic particles were found to have a 2.8 nm average diameter and a narrow size distribution. The size was similar to Pt monometallic particles, and the shape was similar to Pd monometallic particles, both prepared by ultrasound in the same way.

Optimization of Image Contrast for Size Distribution Measurements of Nanomaterials by Transmission Electron Microscopies Including TEM and T-SEM

The regulations on nanomaterials, which started in several EU countries based on the definition of nanomaterial by European committee [1], have now become important issue in nano-related industry. Because, to check if a specimen meets the definition or not, we need to measure its size distribution to count the number of particles of 1100 nm in diameter. Due to technical difficulties, there are increasing discussions to find the solution for the size distribution measurements [2]. In some possible methods, transmission electron microscopy (TEM) and scanning electron microscopy (SEM) are regarded as effective tools due to their capability to easily and quickly observe individual nano-particles [3].