Mine Nakagawa

Electrocatalytic properties of ultrafine gold particles towards oxidation of acetaldehyde and ethanol

Abstract The structural and electrocatalytic properties of ultrafine gold particles deposited onto a flat glassy carbon support (Au/GC) were investigated by means of high-resolution scanning electron microscopy (SEM) and cyclic voltammetry (CV). Gold particles of the Au/GC electrodes prepared had a hemispherical shape and were 1–12 nm in diameter. The mean particle size d decreased with decreasing amount of gold deposited M . In alkaline solutions, these electrodes oxidized acetaldehyde and ethanol anodically at the surface, when covered incompletely with the gold oxide layer. Their electrocatalytic activities per real surface area S Au increased with increasing M , or d so as to exceed those of a gold wire electrode.

Mapping of multiple-quantum-well layers and structure of V defects in InGaN/GaN diodes

Cathodoluminescence mapping reveals threading defects, frequently formed by the lattice misfit between GaN and sapphire substrate, as a dark contrast connected with changes in the energy state. Multiple quantum wells, 2.5 nm In0.25Ga0.75N and 13.9 nm GaN layers, are resolved in the secondary electron image as well as in the backscattered electron image. The backscattered electron image, providing compositional mapping without surface effects such as cleaved steps, reveals the presence of V defects and confirms the thin six-walled structure of the V defect with InGaN/GaN {1011} layers. These scanning electron microscopy observations can be performed after very simple specimen preparation, namely just cleaving the sapphire substrate with the epilayers.

High-resolution scanning electron microscopy observation of GaN/AlGaN strained-layer superstructures in GaN-based violet laser diodes

Two hundred coupled layers of n-Al0.14Ga0.86N (3 nm)/n-GaN (3 nm) strained-layer superstructures (SLSs) with a n-GaN:Si layer were grown directly on a (0001) sapphire substrate by metalorganic vapor-phase epitaxy. With the aid of image processing, each SLS was definitely resolved as a bright or dark fringe 3 nm wide in the mapping of secondary electrons in a high-resolution scanning electron microscope.

A Study of the Behavior of SE and BSE in UltraLow Landing Voltage Condition

In the study, we set our motivation to consider the mechanism to explain such an interesting phenomena particularly happened at the ultra low voltage situation. At first we gathered a set of SE and BSE images simultaneously at ultra low voltage condition from various kinds of specimen. Second, we compared the SE and BSE image to investigate the difference. A simulation results by CASINO [3] was also applied for the theoretical consideration. In the study the recent cold FE-SEM (Hitachi SU8000) is used. The SEM is offering the SE/BSE filtering capability even at ultra low voltage condition as shown in Fig.1.

A Study of Beam Sensitive Materials Using High Resolution, ULV Scanning Electron Microscopy

Low voltage scanning electron microscopy has become common both for topmost surface imaging and reducing beam damage [1]. Lately, high resolution, ultra-low-voltage (ULV) imaging (less than 500 V) has been realized by beam retarding [2] and/or boosting [3] techniques. In this study, some beam sensitive materials are observed by the Hitachi S-4800, which employs a cold field emission source, snorkel type objective lens and a retarding function [4].

Low voltage, high resolution SEM imaging for mesoporous materials

Mesoporous silicas (MPSs), which possess highly ordered structures with a pore size of 2–15 nm, must be widely applied to catalysts, adsorbents, membranes, and sensors. Direct SEM observation of MPSs provides detail information on the external and internal structures, though it consistently faces charge-up problems of insulating silica frameworks. Several skills such as choosing low resistance substrate or replica method succeed to avoid charge-up phenomena [1]. In this contribution, high resolution, direct SEM imaging of MPSs is tried under the condition of low voltages. A cold FEG SEM, which employs the snorkel type objective lens, retarding device [2] and E cross B (ExB) filter [3] for detecting secondary electron (SE) are used for this study.

New evaluation method for the depth of field in terms of the information-passing capacity

A new evaluation method for the depth of field in a scanning electron microscope (SEM) images in terms of the quality of an optical image is introduced. The depth of field, in our method, is evaluated by calculating the image resolution along the optical axis defined in terms of the information passing capacity (IPC) of an optical system. The IPC corresponds to the mean information content included in an optical image, i.e., the quality of the image, evaluated based on the theory of Linfoot. The depth of field in a high resolution observation evaluated by our method depends on the accelerating voltage of the primary beam and signal- to-noise ratio of the image. The calculated results has agreed well with experiment.