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Notes: The lattice disorder in GaP produced by fast neutrons with a fluence of 2.1×1018 cm−2 has been investigated with 1.5 MeV 4He+ channeling. The slight increase in the 〈111〉 aligned yield for irradiated crystals indicates that each primary knock-on (PKO) produces approximately 7×102 displaced atoms. Channeling studies also show a spread distribution of randomly located defects imbedded in the lattice structure. On the other hand, P antisite (PGa) defects produced by neutron irradiation are ∼2 per PKO. Irradiated samples also show a volume expansion of 0.13%. It is suggested that the lattice expansion mainly induced by vacancy–interstitial clusters arises from the displacement atoms rather than PGa defects. © 1999 American Institute of Physics.

Notes: Redshift of the longitudinal optical (LO) phonon relating to the defect structure in neutron-irradiated GaP has been studied using Raman scattering, electron paramagnetic resonance, x-ray diffraction, and Fourier-transform infrared absorption methods. The defect structure is discussed for the two cases of vacancy-interstitials and antisites using a simple model of the LO–transverse optical phonon frequency splitting (Δω). It is suggested that the slight reduction of Δω originates from the vacancy-interstitial clusters rather than the antisite defects, considering the annealing behavior of the antisite defect concentrations, the volume expansion, and infrared absorption in neutron-irradiated samples. The clusters are associated with a volume expansion of about 0.13% observed in the neutron-irradiated samples. © 1999 American Institute of Physics.

Notes: Many practical applications using giant magnetoresistance (GMR) have been developed, such as read-out heads and spin valve devices; however, the origin of GMR is not still fully understood. The GMR effect seems to be originated from the spin scattering mechanism whether at the interfaces or at the layer bodies. Therefore, it is necessary to investigate the spin scattering behaviors at the interfaces in GMR multilayers. It is regarded that the mixing and the diffusion of atoms at the interfaces in multilayers can be well promoted by ion bombardment to the interfaces at proper energy in dual ion beam sputtering (DIBS) method. In this study, change of magnetoresistance (MR) and crystallographic characteristics induced by interfacial mixing of atoms were investigated. Specimen films were deposited by DIBS. Additional ion bombardment to the growing surfaces arranges the mixing effect at the interfaces between Ni-Fe and Cu layers. Acceleration voltage of sputtering ion source Vmg were set at 500 V and that of bombarding ion source Vsg was varied in the range of 0–300 V. Si wafers were used as substrates. Ni–Fe/Cu multilayers with GMR were deposited on 50 A(ring) thick Fe buffer layers.Only two monolayers at the interfaces in Ni–Fe/Cu multilayers were exposed to ion bombardment to cause the local interfacial mixing. X-ray diffraction diagrams, showed that (111) orientations of Ni–Fe and Cu crystallites are obtained at Vsg below 200 V and that, on the contrary, (100) orientation became dominant in the films deposited at Vsg above 200 V. There is no apparent differences in MR ratio with increase of Vsg. However, the field sensitivity and saturation field properties were drastically degraded at Vsg above 200 V, while the crystal structure seemed to be changed. These results indicate that spin scattering were mainly occurred at the layer bodies in Ni–Fe/Cu multilayers. These results implied that the interfacial mixing is not so effective for changing MR ratio of Ni–Fe/Cu multilayers. However, the behavior of magnetization vectors are much influenced by change of local structure at the interfaces. These results seem to confirm the proposed theory; i.e., the spin scattering in layer bodies is the dominant mechanism on GMR in Ni–Fe/Cu multilayers. © 1996 American Institute of Physics.

Notes: Electron cyclotron resonance plasma chemical vapor deposition enables low-temperature SiNx deposition on Hg1−xCdxTe (MCT). The SiNx film has an excellent interface on MCT with a low surface state density of 1.0×1011 cm−2 eV−1 and a low fixed charge of −1.4×1011 cm−2. A detailed analysis by x-ray photoelectron spectroscopy and Auger electron spectroscopy spectra of Te, Cd, and Si at the SiNx/MCT interface indicated that the SiNx deposition reduces the naturally grown MCT native oxide. The oxygen taken from Te oxidizes SiH4 and produces silicon oxides which remain in the SiNx film. Since a chemical shift caused by oxidized Cd at the fresh surface of MCT is very slight, intentionally oxidized samples were used to confirm the above reaction. The analysis of the shape of the Si(2p) peak at the interface indicated that the silicon oxides are composed of SiO and SiO2. Thermodynamic considerations support such a mechanism.

Notes: Magnetic detection has been investigated for use in detecting the location of underground pipelines, such as gas and water lines, by inputting a signal current into a pipeline and detecting magnetic field ((approximately-less-than)100 μG) generated by that current. Measurement factors necessary for accurate detection have been experimentally determined and are discussed. From measurements made on signal current distribution (the current flowing in pipes and leaking from them to ground), it has been concluded that detection error is caused by the leakage current, namely, the current to ground. The detection error is due to the noncenter symmetric distribution of the ground current flowing around a pipe. Even though the ground current is inevitable when flowing a signal current into pipes, it is possible to reduce the error by reducing the nonsymmetry by lowering the signal frequency below 10 kHz in this work. The ground current distribution was obtained by measuring the potential difference between two electrodes, both of which were rod shaped and inserted in the ground to the same depth. At low frequencies below 10 kHz, the ground current distribution in a cross section perpendicular to the pipe showed a rather center symmetry around the pipe, while at high frequencies the distribution changed to a noncenter symmetry with a significant current increase in a region near the ground surface. The drastic change in the distribution of the ground current was also confirmed by magnetic field distribution measurements conducted on the ground using three orthogonally arranged magnetic sensors, each with a sensitivity of 1 μG.

Notes: Recently, it becomes more important to locate the complex piping patterns such as tee, bend, riser, and the others with high accuracy for maintenance and protection of city gas pipelines. Hence, we have developed a new pipe locator system for imaging the complex underground pipelines using magnetic remote sensing techniques. The main framework of this development is the application of the pattern recognition of the magnetic field distribution to the location of buried pipelines in urban areas. The first step for imaging the complex pipelines is to measure the three-dimensional magnetic field distribution with high accuracy which is generated by the passage of the alternating signal current through buried pipeline. For this purpose a portable trolley unit which is capable of scanning the ground to collect data, the 10 three-axes coil sensors with a sensitivity of 1 μG which are aligned in the unit, and a filter system using a FFT signal processor which eliminates urban magnetic noise as high as 10 mG in some cases, were developed. The second step is to process the magnetic field distribution data, to extract the feature of the underground pipeline using the contour diagram and the three-dimensional drawing of the magnetic field, and to identify the complex piping patterns. Further, we recognized that a nonlinear least-square method algorithm for calculation of the pipeline's position was useful to improve the location accuracy.

Notes: Scanning hot electron microscopy (SHEM) has been proposed as an experimental technique which allows for detection of hot electrons emitted from a subsurface semiconductor structure, thus making it possible to obtain the spatial distribution of hot electrons in a device. Here we present the experimental evidence of SHEM operation. Hot electrons with energies of 3 eV are injected by means of a Si/CaF2/Au heterostructure and subsequently detected at the tip of a scanning tunneling microscope in the SHEM configuration. The measured hot electron current was approximately 4 pA for a tunnel current of 5 nA. These results, although still of a preliminary nature, show the potential of SHEM as a technique suitable for the visualization of electron wave effects in semiconductor structures. © 1996 American Institute of Physics.

Notes: We propose a new structure of LiNbO3 guided wave second-harmonic generation device, in which the fundamental light beam is sufficiently confined by two distributed Bragg reflectors (DBRs) formed at input and output ports. The 40% increase in the conversion compared with a conventional device without DBR was achieved under a quasi-phase matching condition.

Notes: There is increasing evidence for the role of basophils in the pathogenesis of bronchial asthma. To examine the presence of basophils in the airways of patients with fatal asthma by immunohistochemistry, we stained lung tissues from four post-mortem cases who had died from severe asthmatic attacks and four controls with a monoclonal antibody raised against tryptase (AA-1) and anti-IgE. Mast cells and basophils were identified in the bronchioles as A A-1- and anti-IgE-positive cells, and anti-IgE-posilive cells, respectively. Airway mast cells were found beneath the basemenl membrane, near blood vessels in the submucosa, and adjacent to the submucosal glands, and scattered throughout the muscle bundles. There was a significant increase of mast cells in the asthma group compared with the control group (203.5 ± 84.6/mm2, mean ± s. d. vs 37.7 ± 8.7/mm2, P 〈 0.05, n= 4). In contrast, basophils were observed in the airway lumen, in the bronchial epithelium and in the submucosa. The number of basophils in the bronchioles was 81.8 ± 55.5/mm2 (n= 4); however, basophils were not found at all in the airways of the control group. Although eosinophils, B lymphocytes and macro-phages bear low affinity IgE receptors and could react with anti-IgE, the location of these cells in the close sections did not correspond closely with basophils. The presence of basophils in lung tissues obtained from fatal asthma patients supports the view that basophils play a role in the pathogenesis of bronchial asthma.