Koyata Takahashi

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.

A Structural Study of Co-Sb Multilayered Film by X-Ray Diffraction

The structure of a multilayered film, [Co(30 ?)-Sb(25 ?)]70, prepared by vacuum deposition is investigated by using mainly X-ray diffraction. It is revealed that the Co layer has a hcp structure with [110] texture while the Sb layer does not show any distinct texture. The relative intensities and the line width of Bragg reflections are interpreted on the assumption of a very thin compound layer at each interface and also a small distribution of Sb layer thickness. Preliminary results from electron microscopic analyses are also briefly introduced.

The Influence of the Rear Mask on Copying Recorded Marks for Magnetically Induced Superresolution Disks

Magnetically induced superresolution (MSR) disks by double masked rear aperture detection (D-RAD) sometimes show direct transition from the initialized state to the D-RAD state in the readout power curves. Peak and trough levels of read signals for these MSR disks were measured and the states of the aperture and the rear mask during the readout were clarified. When the read field is in the erase direction, the aperture opens simultaneously with the collapse of the mark in the rear mask. When the read field is in the write direction, copying a mark from the recording layer to the readout layer starts as the mark in the recording layer overlaps the rear mask and the successive wall displacement copies the mark. The MSR with the latter mechanism was found to be very effective for eliminating crosstalk.

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.

Influence of Groove Shape on Rear Expansion Detection Readout

We have investigated the influence of groove shape and recording scheme on readout of rear expansion detection (RED) magneto optical media. Marks recorded by laser pulse magnetic field modulation (LP-MFM) were found to expand without a field while those recorded by light intensity modulation (LIM) required a field for expansion. Media with steep wall grooves showed a high carrier-to-noise ratio (CNR) of 42.7 dB at a mark length of 0.2 µm when recorded by LP-MFM and required a low readout field of less than 100 Oe even when recorded by LIM.

Tuning of the trilayer D-RAD MO disk to readout with write direction field

The Double-masked Rear Aperture Detection (D-RAD) with write direction field enables very low crosstalk as well as high resolution. In this paper, composition and sputtering condition of trilayer magnetic films were investigated to obtain stable D-RAD readout with adequate read power margin. The method for evaluating the stability of the front mask was also investigated to achieve a sharp and uniform front mask.

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.