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Retention of the enhanced properties reported for nanograined metallic systems requires that the nanostructure be insensitive to temperature and deformation. In situ transmission electron microscopy annealing experiments were employed to investigate the structural changes associated with the formation of micron-sized grains in nanograined evaporated gold thin films. This abnormal grain growth occurs randomly throughout the film. Twinning but not dislocation slip occurs in the growing grains until the grain size is in the hundreds of nanometer range. The twins appear to hinder growth and for grain growth to continue the twins must either be annihilated or be able to grow with the grain concurrently.
One of the most widely studied types of magnetic nanostructure is that used in devices based on the giant magnetoresistance (GMR) or tunnel magnetoresistance (TMR) phenomena. In order to understand the behaviour of these materials it is important to be able to follow their magnetisation reversal mechanism, and one of the techniques enabling micromagnetic studies at the sub-micron scale is transmission electron microscopy. Two techniques can be used: Lorentz transmission electron microscopy and off-axis electron holography, both of which allow the magnetic domain structure of a ferromagnetic material to be investigated dynamically in real-time with a resolution of a few nanometres. These techniques have been used in combination with in situ magnetizing experiments, to carry out qualitative and quantitative studies of magnetization reversal in a range of materials including spin-tunnel junctions, patterned thin film elements and magnetic antidot arrays. Quantitative analysis of the Lorentz TEM data has been carried out using the transport of intensity equation (TIE) approach.
Mode I cracks introduced in Si at the ductile-brittle transition temperature (DBTT) have been examined extensively using transmission electron microscopy. Cross-sectional as well as plane-view specimens suitable for the observation were prepared using a focused ion beam technique. Many small dislocation loops nucleate at the fracture surface of a mode I crack during the propagation at DBTT.
Microtribology of Silicon single crystals is one of the important factors for the practical use of MEMS. In this study, the effect of crystal orientation on microwear of Silicon single crystal and the wear structure were mainly investigated. Microfriction experiments using atomic force / friction force microscope (AFM / FFM) were carried out to investigate the effect of crystal orientation on the microwear depth of Silicon single crystals. In these experiments, the scanning-scratching directions of a tip of AFM / FFM were <100> and <110> on Si(100) surface and <112> on Si(111) surface. As a result, it was found that the depth of the wear marks generated on Silicon surfaces increased in the following order: <112>, <100>, <100>. Cross-sectional TEM observations of the microwear marks were carried out. As a result, it was found that the small dislocation loops were generated in the surface region at the first stage of the microwear, and the size and the number of dislocations increased with the progress of the microwear.
The recent attention paid to stress migration of aluminum (Al) electrodes in thin-film transistor liquid crystal display (TFT-LCD) applications indicates that wiring materials with low electrical resistivities are of considerable interest for their potential use in higher-resolution displays. In this paper, we firstly describe how as-grown Al whiskers on Al electrodes fabricated on a LCD-grade glass substrate can be characterized by means of a high-voltage transmission electron microscope (HV-TEM) operated at 1 MV. The whiskers ranging from 300 to 400 nm in diameter are sufficient to be transparent to high-voltage electrons. This allows detailed observation of whisker characteristics such as its morphology and crystallography. In most cases, the as-grown Al whiskers in our study had straight rod shapes, and could be regarded as single crystals. Secondly, we report on the in-situ fabrication and observation of Al whiskers at elevated temperature with the HV-TEM. Since relatively thick TEM samples (up to about 1 mm) can be set on a sample holder in the HV-TEM, various growth stages of Al whiskers can be investigated under various heating conditions. Finally, we demonstrate a TEM sample preparation method for the cross-section of an individual Al whisker, using focused ion beam (FIB) etching. This technique makes it possible to reduce the thickness of an Al whisker close to the root. Both bright- and dark-field TEM images provide nanostructural information on the whisker/Al thin-film interface.
The relation between the nanostructure of pure Al and Al-0.2 wt.% Cu thin films on glass substrates and anti-stress migration properties were investigated. These films were deposited on liquid-crystal display (LCD) grade glass substrate (550 x 650 mm) by means of two types of dc magnetron multi-chamber sputtering apparatus.
We developed the nanoindentation techniques to accelerate the characterization time for stress migration test. By AFM and cross-sectional TEM observations, we found an unusual three-layer structure in a Al-Cu thin film with strong anti-stress migration property.
Annealing effects on Al-Nd (0.19 – 1.82 at. %) thin films deposited on a glass substrate have been investigated. It is found that the resistivity of an Al-Nd-alloy thin film decreases significantly after annealing at 300 °C or higher temperatures. Using cross-sectional transmission electron microscopy (X-TEM), we have observed segregation of Al-Nd inter-metallic precipitates and pure-Al grains during the annealing. The decrease of the resistivity can be attributed to the segregation. Segregation has been also detected from the increase of diffracted X-ray intensities corresponding to Al-Nd inter-metallic compounds in X-ray diffraction (XRD) analysis. Atomic force microscopy (AFM) observation has revealed that the optimum content ratio of Nd in Al-Nd alloys used as interconnect materials for thin-film-transistor liquid crystal display (TFT/LCD) applications is around 0.97 atomic %.
Hydrogenated amorphous silicon thin-film transistors (a-Si:H TFTs) are now widely used as elements for active matrix liquid crystal displays. The nanometer-scale multilayered structure of a-Si:H TFTs has been characterized by cross-sectional transmission electron microscopy (TEM). The discrete layer construction of a faulty TFTs and the generation of defects during manufacturing processes have been investigated. A combination of focused ion beam (FIB) etching and cross-sectional TEM leads to a successful failure analysis. A contamination layer with a thickness of 10–30 nm and microvoids inside multilayers are identified in faulty TFTs. An a-Si layer on silicon nitride (SiNx) is crystallized during TEM observation. Electron energy loss spectroscopy analysis indicates that the diffusion of nitrogen into a-Si layer causes the crystallization.
A rapid and precise sample preparation method using focused ion beam (FIB) etching was developed for cross-sectional transmission electron microscopy (X-TEM) analysis of a thin-film transistor (TFT) fabricated on a glass substrate. Gallium (Ga) ions accelerated at 30 kV and at various incident beam angles were applied during FIB etching to create a uniform thin wall. We successfully prepared X-TEM specimens of long and fragile aluminum (Al) whiskers formed on thin Al films in TFT metallization, where a strong charge is built up during FIB etching. The effect of ion-beam-assisted tungsten deposition prior to FIB etching is discussed. A whisker having a length not exceeding approximately 10 #x00B5;m can be successfully etched to a thickness of 200 nm while keeping its original shape. The performance of this technique is demonstrated in applications to etching at other fragile locations related to TFTs.
In this study, the microstructural change of the surface of Si single crystal (Si(100)) after the scratching tests under very small loading forces was investigated. At first, line-scratching tests and scanning-scratching tests were carried out using an atomic force/friction force microscope (AFM/FFM). Next, cross-sectional TEM observations of the wear marks which were generated by the scratching tests were carried out. As a result of the TEM observations after the line-scratching tests, it was found that dislocations were observed in the area of less than 100nm thickness from the surface of the wear marks which were formed under the loading forces of more than 5μN. In the case of the loading forces of more than 20μN, an amorphous region was also observed just under the wear marks. As a result of the TEM observations after the scanning-scratching tests, it was found that the introduction of dislocations took place and no amorphous region appeared. It was also found that the several atomic layers at the top surface of the wear marks shifted in parallel to (100).
In March 1989 a large outbreak of acute gastroenteritis occurred simultaneously among schoolchildren and teachers at nine elementary schools in Toyota City, Japan. Illness was observed in 3236 (41·5%) of 7801 schoolchildren and 117 (39·4%) of 297 teachers. The main clinical symptoms were diarrhoea, vomiting, nausea and abdominal pain. Gastroenteritis was significantly associated with the consumption of school lunch served by one particular lunch preparation centre. One food handler at the centre suffered from gastroenteritis during the outbreak.Small round structured virus (SRSV) was detected in 4 of 8 stool specimens from sick persons. The school lunch contaminated by the infected food handler is the most probable source of this outbreak due to SRSV.
The inhibitory influence of cyanuric acid on the virucidal effect of chlorine was studied. The time required for 99·9% inactivation of ten enteroviruses and two adenoviruses by 0·5 mg/l free available chlorine at pH 7·0 and 25○C was prolonged approximately 4·8–28·8 times by the addition of 30 mg/l cyanuric acid. Comparative inactivation of poliovirus 1 by free available chlorine with or without cyanuric acid revealed the following. The inactivation rate by 1·5 mg/l free available chlorine with 30 mg/l cyanuric acid or by 0·5 mg/l free available chlorine with 1 mg/1 cyanuric acid was slower than by 0·5 mg/1 free available chlorine alone. Temperature and pH did not affect the inhibitory influence of cyanuric acid on the disinfectant action of chlorine. In the swimming-pool and tap water, cyanuric acid delayed the virucidal effect of chlorine as much as in the ‚clean’ condition of chlorine-buffered distilled water. The available chlorine value should be increased to 1·5 mg/l when cyanuric acid is used in swimming-pool water.
We studied, for two years, the prevalence of indigenous human enteric viruses in wild oysters gathered each month from the bottom of Mikawa Bay, Aichi Prefecture, Japan. Viruses were detected periodically in 9 out of 54 oyster pools prepared by the acid or polyethylene glycol precipitation method although all these 9 pools met current national bacteriological safety standards. Since most of the serotypes of the enteric viruses detected in the oysters were identical with those of viruses isolated from sick children living in the area, it is suggested that contamination of enteric viruses in the oysters would depend on the prevalence of enteric viral infections in the local inhabitants.
The significant contribution of pig production in the supply of high quality protein in Nigeria is evident in the rapid increase in number of pig farms witnessed recently. However, African Swine Fever (ASF) has since ravaged pig farms and consequently resulted in loss of farmers’ investments especially in some parts of the Southwest Agro-ecological zone of Nigeria (Majiyagbe et al., 2004; Otesile et al., 2005; Olugasa and Ijagbone, 2007). Putting the growth of the enterprise back on track requires proper assessment of the socio-economic environment surrounding the spread of the disease with the aim of determining the extent of infection, the consequences in terms of mortality of animals and loss of revenue alongside identifying farm specific factors that could have contributed to the spread. This study thus investigated the incidence of ASF and its socio-economic implications on pig enterprise in the zone.
Growth of bismuth oxide (most probably Bi2O3) was observed in situ in a transmission electron microscope. Bi liquid particles were dispersed on the substrates of diamond or SiO2. Introduction of oxygen up to ∼5 × 10−4 Pa resulted in formation of bismuth oxide (most probably Bi2O3) whiskers. The growth mechanism of the whisker was discussed in terms of a vapor-liquid-solid (VLS) mechanism. It is suggested that the liquid droplet of Bi acts as a physical catalyst for growth of bismuth oxide (most probably Bi2O3) whiskers.