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Methods for the control of molecular deposition and orientation are critical for the development of organic electronic devices. Here, we show the fabrication of ribbons of the optical material polydiacetylene (PDA) using a controlled evaporative self-assembly method. The ability to form these ribbons is highly dependent on both the side groups on the PDA as well as the solvent used in the preparation. Arrays of ribbons of one type of PDA, poly[1,6-di(N-carbazolyl)-2,4-hexadiyne], with widths on the order of 1–2 µm and lengths of 100s of micrometers, could be successfully obtained with good orientation.
Mapping observations of nearby large-extended clusters of galaxies (Coma, Perseus, Virgo, etc.) are being performed with ASCA. Such clusters allow us to map physical parameters of hot gas in the clusters, such as temperature, metal abundance, and X-ray surface brightness. To determine such parameters at each part of a cluster, one should take careful care of X-ray contamination from outside of a pointed field, which is mainly due to “stray-light” X-rays (Honda et al. 1997). For this reason, the only way to obtain the distribution of hot gas parameter is to process the whole cluster data in a self-consistent way. For this purpose, we are developing the new analysis system called TERRA.
The Coma cluster has been recognized as an archetype of rich and relaxed clusters, until recent ROSAT observations reveal that the intracluster medium (ICM) has a complex distribution (Briel et al. 1992; White et al. 1993). The X-ray surface brightness distribution shows a secondary peak around the galaxy NGC 4839, at 40' SW from the cluster center.
In the Virgo cluster, we can perform a close study of the gas injection mechanism from galaxies into the cluster space and the interaction between the injected gas and the sorrouding cluster medium. In 1996 to 1997, we carried out mapping observations of a 2.°5 × 2.°5 area in the north-west region of the cluster. There are 16 pointings in total in this region, and the observed results are briefly reported here.
STJs are promising X-ray detectors as high energy resolution spectrometers due to the small excitation energy to break the Cooper pairs to product detectable electrons. The expected energy resolution is about 5 eV for a 6 keV incident X-rays (see review by Kraus et al. and Esposito et al.). We have developed a large area (178 × 178μm2) Nb/Al/AlOX/Al/Nb STJs (Kurakado et al. 1993) and series-connected STJs with a position resolution of 35μm for α particles (Kurakado 1997) at Nippon Steel Corporation. As a focal plane detector in future X-ray missions, we are developing STJs whose targert characteristics are; an energy resolution of 20 eV at 6keV, an effective area of 1 cm2, and position resolution of 100μm.
Liposarcomas rarely occur in the parapharyngeal space and only a few case reports exist. For curative therapy of liposarcoma, surgical excision remains the dominant modality. Although a wide surgical margin is important to prevent local recurrence, wide excision is often difficult in the head and neck region.
We report a case of a 19-year-old female with a well-differentiated liposarcoma arising in the parapharyngeal space. We removed the tumour surgically utilising a cervical–parotid approach. The histological diagnosis was well-differentiated sclerosing liposarcoma. There is no recurrence after five years and nine months of follow up.
The patient's age and the tumour site made it difficult for us to make a quantitative diagnosis before the operation. Well-differentiated liposarcoma rarely develop distant metastasis, but often recur locally. The benefit of adjuvant radiotherapy for well-differentiated liposarcoma is still not clear and careful and long-term follow up is necessary.
Lead-free, piezoelectric (Na,K)NbO3-BaZrO3-(Bi,Li)TiO3 films were epitaxially grown onto (100) SrTiO3 substrate via pulsed laser deposition. The effects of post-annealing temperature on the crystal phases, mosaic spread, and chemical composition of the deposited (Na,K)NbO3 and (Na,K)NbO3-BaZrO3-(Bi,Li)TiO3 films were analyzed. Results indicate the epitaxial growth of (Na,K)NbO3-BaZrO3-(Bi,Li)TiO3 films deposited at an oxygen pressure (PO2) of ≥40 Pa and substrate temperature (Ts) of 800°C. The alkaline-deficiency could be suppressed in the (Na,K)NbO3-BaZrO3-(Bi,Li)TiO3 films deposited at PO2 ≥ 70 Pa. AFM profile of the (Na,K)NbO3 post-annealed at 1000°C indicates the epitaxial growth of film with atomically flat step-terrace structure, while that of the (Na,K)NbO3-BaZrO3-(Bi,Li)TiO3 film post-annealed at 1200°C shows relatively smooth surface with step-terrace structure and several cubic crystals. It was also found that the preferential evaporation of alkaline components could be suppressed by annealing under covered substrate condition.
We examined the potential application of CuIn1-xGaxSe1-ySy (CIGS) film for visible light image sensors. CIGS chalcopyrite semiconductors, which are representative of high efficiency thin film solar cells, have both a high absorption coefficient and high quantum efficiency. However, their dark current is too high for image sensors. In this study, we applied gallium oxide (Ga2O3) as a hole-blocking layer for CIGS thin film to reduce the dark current. The dark current of this hetero-junction was 10-9 A/cm2 at less than 7 V. Moreover, an avalanche multiplication phenomenon was observed at an applied voltage of over 8 V. However, this structure had sensitivity only in the ultraviolet light region due to the much lower carrier density of the Ga2O3 layer. We therefore used a tin-doped Ga2O3 (Ga2O3:Sn) layer deposited by pulsed laser deposition (PLD) for the n-type layer to increase the carrier density. The sensitivity of the visible region was observed in the Ga2O3:Sn/CIGS hetero-junction. We also investigated the influence of the laser frequency of the PLD on the transmittance of Ga2O3:Sn and the quantum efficiency of this hetero-junction. Ga2O3:Sn film deposited at a 0.1-Hz laser repetition rate had higher transmittance than at a 10-Hz repetition rate. The Ga2O3:Sn/CIGS hetero-junction also had a higher quantum efficiency with the lower rate (50%) than with the higher rate (30%).
(Na,K)NbO3 is a promising candidate for lead-free piezoelectric materials. (Na1-xKx)NbO3 films (x = 0.3–0.7) were epitaxially grown on a (100)SrTiO3 substrate via pulsed laser deposition. The effects of substrate temperature and oxygen pressure during deposition on the crystallinity of the films were examined: both parameters affected the mosaic spread of the crystallites and the formation of an impurity phase. In this study, the optimum conditions for the preparation of highly crystalline films were a substrate temperature of 800 °C and oxygen pressure of ∼60 Pa. The lattice constants parallel and perpendicular to the substrate surface responded differently to changes in x: the constant parallel to the surface increased with increasing x, while the constant perpendicular to the surface was maximized at x = 0.5. The difference in the dependence of the lattice constants could be explained by the elastic distortion of the lattice.
The development of an iodine immobilization technique that can fix radioactive iodine in waste form for a long period and constrain its leaching into pore water is necessary in order to secure the long-term safety of geological disposal of transuranic (TRU) waste. Lead borate glass vitrified at a low temperature is regarded as a promising material for immobilizing the Iodine-129 that is recovered from spent AgI filters generated by reprocessing plants in Japan and which may have a significant effect on the long-term safety of geological disposal.
Batch leaching tests were conducted to understand glass dissolution behavior in various solutions that account for geological disposal conditions. Boron dissolved at the highest rate in all types of solutions to be used as an index element for measuring the glass dissolution rate. On the other hand, lead dissolved in these solutions at a much lower rate. These results are consistent with an electron micro-probe analysis (EPMA) of the altered glass surfaces that indicated the depletion of boron and enrichment of lead near the surfaces.
The altered glass surfaces were further examined by scanning and transmission electron microscopy (SEM/TEM) and X-ray diffraction (XRD). SEM/TEM observation showed formation of a porous altered layer consisting of fine crystallites on the pristine glass and euhedral crystals on the altered layer. XRD analysis indicated that the fine crystallites and euhedral crystals are hydrocerussite, Pb3 (CO3)2(OH) 2, which was predicted by geochemical calculation as the precipitate for the experimental system.
This paper presents several examples of defect analyses carried out in actual VLSI failure analyses and experiments, using TEM technique, process simulation and other advanced analytical tools. New TEM techniques are also described to observe a precise location which has failed.
Pressure induced structural phase transformation in nanocluster assembled GaAs is studied using parallel molecular dynamics simulations in the isothermal-isobaric ensemble. In this system the spatial stress distribution is found to be inhomogeneous. As a result structural transformation initiates in the high stress regions at the interface between clusters. Structural and dynamical correlations in the nanophase system are characterized by calculating the spatially resolved bond angle and pair distribution functions and phonon density of states and comparing them with those for a single cluster and bulk crystalline and amorphous systems.
The surface morphologies of homoepitaxial GaN films grown by molecular beam epitaxy (MBE) on metalorganic chemical vapor deposition (MOCVD) grown GaN template layers were investigated, using atomic force microscopy (AFM). Typical surface morphology of MBE-grown films on MOCVD-templates was dominated by spiral hillocks due to the high density of dislocations having a screw character and large driving force of MBE growth. Introduction of the AlN multiple interlayer (AlN -MIL) into MBE-GaN layers suppressed the formation of spiral hillocks. It was attributed to obstructing the dislocation propagation by AlN-MIL. Migration enhanced epitaxy (MEE) growth of GaN also reduced the density and tightness of spiral hillocks. This observation was attributed to that MEE growth technique decreased the driving force of growth.