Yoshinobu Mori

Cathodoluminescence and electroluminescence of undoped and boron‐doped diamond formed by plasma chemical vapor deposition

Visible luminescence between 2.0–3.5 eV of undoped and boron‐doped diamond formed by plasma‐assisted chemical vapor deposition has been investigated by cathodoluminescence. Electroluminescence from Schottky diode of boron‐doped semiconducting diamond has been observed for the first time and found to be due to the same luminescent center as that of cathodoluminescence. In the particles or films where the content of nitrogen and boron was greatly reduced, the cathodoluminescence peaks occurred at 2.8–2.9 eV. The characteristics of these emission spectra are very similar to those obtained in type‐IIa diamond where dislocations are luminescent. The doping of boron during the deposition form another luminescent center at 2.3–2.4 eV. From the monochromatic cathodoluminescence imaging, the luminescent regions differ in the two peaks. {100} sectors are much more luminescent than {111} sectors at the signal of 2.8 eV. This phenomenon has been discussed based on the difference in defect or impurity concentration of...

Planning for PACS at Osaka University Hospital

We have a plan to adopt PACS as a medical image information system in the new hospital. In order to construct PACS suitable for our hospital, a preliminary survey was carried out to determine how PACS should be introduced and what are the physicians requirements for a new medical image system. The most important requirement of the physicians was a good quality workstation. Our plan of a new medical image information system is as follows. A primary database will be constructed according to each of modalities in the Department of Radiology. In the Department of Medical Information Science, we will make a secondary database according to the patient. Although it may be difficult for us to obtain a sufficient budget digitalizing all medical images by our move to the new hospital, our goal is to establish total PACS throughout the new hospital in 1995.

Technology assessment of PACS in Osaka University Hospital

This paper describes a methodology of PACS technology assessment and gives examples of the results of measurement of 24 items of PACS-related situations of image diagnosis systems in Osaka University Hospital before a PACS is installed. These data are to be compared with the data which will be measured after PACS is installed in the new Osaka University Hospital, in order to complete our technology assessment. We propose common variables, units, and conditions of measurement, in order to establish a standard method of data comparison between before and after PACS installation in hospitals at large. We designed our PACS taking technology assessment into account. We do not stop the technology assessment at the efficacy evaluation, because PACS must be more than a tool for radiological practice. We extend the technology assessment into the effectiveness evaluation, so that PACS is a part of radiological practice itself, and diagnostic accuracy, economy and efficiency are the results of PACS operation.

A first-principles investigation on the mechanism of nitrogen dissolution in the Na flux method

The origin of the drastic enhancement of the N solubility in Na-rich GaxNa1−x liquid alloys compared to pure Ga and Ga-rich alloys is clarified using density functional theory. Liquid simulations show that Ga atoms tend to aggregate in Ga-rich alloys, while Ga atoms are isolated or form small clusters in Na-rich alloys. The calculated N solubility for model crystals shows good agreement with the experimental results. In Ga-rich alloys, the interaction between Ga and N is weak because Ga interacts strongly with surrounding Ga atoms. In Na-rich alloys, Ga–N bond becomes strong because Ga is chemically active, leading to the enhancement of the N solubility.

Dislocation confinement in the growth of Na flux GaN on metalorganic chemical vapor deposition-GaN

We have demonstrated a GaN growth technique in the Na flux method to confine c-, (a+c)-, and a-type dislocations around the interface between a Na flux GaN crystal and a GaN layer grown by metalorganic chemical vapor deposition (MOCVD) on a (0001) sapphire substrate. Transmission electron microscopy (TEM) clearly revealed detailed interface structures and dislocation behaviors that reduced the density of vertically aligned dislocations threading to the Na flux GaN surface. Submicron-scale voids were formed at the interface above the dislocations with a c component in MOCVD-GaN, while no such voids were formed above the a-type dislocations. The penetration of the dislocations with a c component into Na flux GaN was, in most cases, effectively blocked by the presence of the voids. Although some dislocations with a c component in the MOCVD-GaN penetrated into the Na flux GaN, their propagation direction changed laterally through the voids. On the other hand, the a-type dislocations propagated laterally and c...

PACS in Osaka University Hospital

To develop the hospital information system, the radiological information system, and the picture archiving and communication system for our new hospital, we analysed the data volume at each step of the flow in our present film-based system. After that, we used a small PACS, and it indicated the problems in it. From the analysis of the data volume of the film-based system, it was found out that digital data should be compressed, and prefetching techniques should be employed for digital PACS. Several types of display terminals had been proved to be necessary for different purposes. An RIS connection was thought to be obligatory to avoid incorrect input of ID on the image. Image input terminals should have edit functions for easy recognition of the image information. Taking account of these requirements for digital PACS, we are developing an actual total PACS.

Structural analysis of ion-implanted chemical-vapor-deposited diamond by transmission electron microscope

Abstract A transmission electron microscope (TEM) study of ion-implanted chemical-vapor-deposited (CVD) diamond is presented. CVD diamond used for transmission electron microscope observation was directly deposited onto Mo TEM grids. As-deposited specimens were irradiated by C (100 keV) ions at room temperature with a wide range of implantation doses (1012–1017/cm2). Transmission electron diffraction (TED) patterns indicate that there exists a critical dose (Dc) for the onset of amorphization of CVD diamond as a result of ion induced damage and the value of critical dose is confirmed to be about 3 × 1015/cm2. The ion-induced transformation process is clearly revealed by high resolution electron microscope (HREM) images. For a higher dose implantation (7 × 1015/cm2) a large amount of diamond phase is transformed into amorphous carbon and many tiny misoriented diamond blocks are found to be left in the amorphous solid. The average size of these misoriented diamond blocks is only about 1–2 nm. Further bombardment (1017/cm2) almost kills all of the diamond phase within the irradiated volume and moreover leads to local formation of micropolycrystalline graphite.

Time and flow study for technology assessment of PACS

Quantitative description of the value of Picture Archiving and Communication System (PACS) in the health care environment is essential to assess the benefits with which PACS provides us. It is necessary to obtain data related to our film-based system before PACS installation in order to make quantitative comparison of before-and-after PACS operation, so that we can assess the clinical effectiveness brought by the PACS itself. We conducted flow study to acquire the whole chart of data flow related to radiological examination. And then defined the parameters and employed them to conduct time study for measuring several items concerning order entry, report making and image delivery at outpatient clinics and wards of eight departments using stopwatches, IC cards and time-recorders. This paper describes the results of measurement. For example, the location of each clinic/ward affected the time spent for images/reports delivery, and that hand writing time occupies more than half of the time required for making a single diagnostic report in 16 percent of cases. These results indicate that acceptability by medical staff is the key to successful operation of PACS. For instance, simple man-machine interaction at image display workstation must be properly realized. By using the same parameters mentioned above, we can compare those data with the results measured after PACS operation in a few years.

Cathodoluminescence Of Vapour-Synthesized Diamond

Cathodoluminescence of diamond films has been investigated in the range of 2.0-3.5 eV. The CL spectra of diamond films are very sensitive to impurities such as nitrogen and boron. The main emission peak occurs around 2.8 eV in the films where the content of these impurities are lowered. The shape and behaviour of the spectra of the films are very similar to those obtained in natural type IIa diamond. The boron doping to the films increases the CL intensity. The luminescence is explained by donor-acceptor pair recombination where the acceptor is substitutional boron. In the semiconducting film, electroluminescence has been observed at metal/diamond(p-type) interfaces for the first time. From the CL imaging study, (100) growth sectors of diamond particle are much more luminescent than (111) sectors. This result indicates that the introduction of impurity or defect during crystal growth differs in each sectors.

Structural modification of ion‐implanted and postannealed polycrystalline diamond studied by transmission electron microscopy

We have presented a convenient and effective method to ex situ study ion‐implanted and postannealed polycrystalline diamond by transmission electron microscopy (TEM) without thinning the specimens. Chemical‐vapor‐deposited (CVD) diamond used for transmission electron microscopy study was directly deposited onto Mo TEM grids, and then implanted and postannealed. TEM images clearly reveal that there exists an ion‐induced amorphous layer on the as‐implanted CVD diamond surface, in which graphitelike structure is embedded. The amorphization processes depend on the irradiation conditions. Hydrogen plasma treatment was employed to anneal the as‐implanted CVD diamond. High resolution electron microscopy images indicate that hydrogen plasma treatment can effectively remove the ion‐induced surface amorphous layer without graphitizing the diamond. After treatment, high density ball‐like diamond blisters appear on the surface, of which the average diameter is only about 2.5 nm, implying the critical size for the sta...