Akio Kondo

Degradation induced by the Sr2+ vacancies in SrS:Ce electroluminescent devices

Abstract The degradation mechanism of SrS:Ce electroluminescent (EL) devices is proposed. Degradation is induced by the Sr2+ vacancies in a SrS phosphor film. The Sr2+ vacancies are formed by Ce doping and S excess deposition condition. Ce has a special influence on Sr2+ vacancy formation in comparison with other trivalent rare-earth ions because of the partial existence of Ce4+. We have found that phosphorus codoping, which quenches the Sr2+ vacancies, drastically improves the stability of SrS:Ce EL devices.

Magnetic Properties and Recording Characteristics of Co-Cr-Ta-Pt Thin Film Media

Magnetic properties and recording characteristics of Co-Cr-Ta-Pt film for high-density recording media were investigated. It was found in this study that high coercivity of more than 1800 Oe can be obtained by addition of 3 at.% Pt and deposition at 250°C. The increase of coercivity by the addition of Pt atoms is considered to be due to the increase of magnetic anisotropy. The cause of high coercivity of the samples deposited at high substrate temperature is considered to be the growth of hcp(11.0) parallel to the film plane. It was also found that Co-Cr-Ta-Pt media had lower media noise level than Co-Cr-Pt media and that the media noise level of Co-Cr-Ta-Pt can be reduced to the same level as in Co-Cr-Ta media by increasing Cr composition.

Magnetic properties and crystal structure of CoCrTaPt thin film for longitudinal recording media

Magnetic properties and crystal structure of sputtered CoCrTaPt/Cr and CoCrTa/Cr thin films were studied as a function of Pt content and the substrate temperature. It was observed that the coercivity increased with Pt content or the substrate temperature, and that the coercivity was saturated with a small amount of Pt at high substrate temperature compared to at low substrate temperature. X‐ray diffraction study showed that at high substrate temperature, Co(11.0) grew epitaxially on Cr(200). That indicates c axis of hexagonal‐close‐packed Co phase lies in the film plane. It was also shown that diffraction angles of Co planes shifted lower with the addition of Pt. These shifts are attributed to the diffusion of Pt into the Co lattice, and the shifts are promoted by the increase of the substrate temperature. The addition of Pt led to the increase of crystalline magnetic anisotropy constant (Ku), and the increase of Ku was also promoted by the increase of the substrate temperature. The increase of the coerci...

Magnetic properties of CoNiPt and CoNiPd thin films

CoNiPt and CoNiPd thin films were investigated for high‐density longitudinal recording media. The samples were prepared by dc magnetron sputtering. Concentration of Pt or Pd was controlled by changing the number of Pt or Pd chips put on the Co 20 at. % Ni target. It was observed that the coercivity of the samples increased with increasing the Pt or Pd concentration. The x‐ray diffraction intensity of Co(002) of the CoNiPt and CoNiPd samples also increased as Pt and Pd content increased, respectively. As a result, it was found that the coercivity increased as the intensity of Co(002) in both films increased. There was no significant difference between CoNi and CoNiPt and CoNiPd films in SEM surface micrographs. The cause of the difference in coercivity may be attributed to the difference in magnetocrystalline anisotropy of the films.

Basic Study of Quantitative Ion Scattering Spectroscopy I Correction Factors for Quantification

Basic problems in quantification by ion scattering spectroscopy (ISS), i.e., energy dependence of the detection efficiency of a micro channel plate (MCP) and neutralization probabilities, have been studied using a newly constructed time of flight (TOF)-ISS apparatus. For primary ion energy below keV (1) marked dependence of the detection efficiency of MCP on the signal energy, and (2) strong contribution, to the ISS spectrum, of those neutral signals that are backscattered through the collision with the second or subsequent atomic layer atoms have been clearly revealed. It has also been pointed out that the energy dependence of the detection efficiency is described very well by a simple statistical treatment of secondary electron generation in the detector.

Copying Characteristics of the Magnetically Induced Superresolution Disk

Copying characteristics of recorded domains from the recording layer to the readout layer were studied for the magnetically induced superresolution disk. It was found that the larger the difference of the wall energy between the switching layer and the readout layer was, the better copying characteristics were. The copying field of a domain tended to be much less than that without or outside of a domain. To explain this behavior, it was proposed that the interface wall within a domain sinks into the recording layer in comparison with the one without or outside of a domain.

Sr1−x Znx S:Ce, F Phosphor for Thin Film Electroluminescent Devices

SrS is one of the most noticed thin film electroluminescent (TFEL) materials. At first, SrS:Ce was found to be an efficient blue phosphor/1,2 /. Although it emits bluishgreen light, its efficiency is 100 times greater than ZnS:Tm blue phosphor. Recently, Tanaka et al. /3/ reported efficient white phosphors which are SrS:Ce,K,Eu and SrS:Pr,K. SrS:Ce,K,Eu especially has a potential of a full color display, because it has a wide range of electroluminescent spectrum from blue to red.

New Neutral- and Ion-Scattering Spectroscopy as Applied to Selective Adsorption of Hydrogen on Cu–Pt Alloy Surfaces

A newly developed time-of-flight system equipped with an accelerating tube was applied to hydrogen adsorption on Cu–Pt alloy surfaces. The simultaneous measurements of the scattered neutrals, Ne0, and ions, Ne+, from adsorbates have shown that selective adsorption of hydrogen on Pt atoms does occur on polycrystalline Cu–Pt alloy surfaces. Correlation of hydrogen coverage with the neutralization of an ISS signal is also discussed.

The effect of additives on MSR performance of GdFeCoM/TbFeCo (M=Ta, Pt) double layer

Magnetically induced super‐resolution performance for a center aperture detection scheme in a double layered magneto‐optical storage is discussed. In order to make a readout layer thinner for better media lifetime, the effect of Ta and Pt additive elements in a readout layer GdFeCo on recording performance is systematically studied. Ta is found to be most effective in making it possible to reduce the readout layer thickness for an acceptable recording performance. For the mark length of 0.5 μm, the thickness can be reduced to 60 nm with Ta (1.9 at. %) from 80 nm without Ta for carrier‐to‐noise ratio (CNR)≥42 dB.