Hidemi Yoshida

High-Density Pulse Width Modulation Recording and Rewritable Capability in GeSbTe Phase-Change System Using Visible Laser Beam at Low Linear Velocity

Write and erase characteristics at low linear velocity in GeSbTe phase-change optical disks have been studied using 488 nm and 680 nm visible lasers. Good characteristics, which are carrier-to-noise ratio (CNR) of more than 50 dB and erasability of more than 25 dB, were obtained by optimizing the composition of GeSbTe and the layer structure. However, smaller erase power margin has been observed in comparison with the case of using a 780 nm laser. From transmission electron microscope (TEM) observation and numerical simulation, it is explained that these phenomena are mainly due to the difference in the temperature profile arising from the beam profile. For pulth width modulation (PWM) recording using a 680 nm laser, the resolution has been improved by 25% in comparison with the case of a 780 nm laser. Furthermore, a clear eye pattern of the eight-to-fourteen modulation (EFM) signal was observed at the 3 T mark length of 0.65 µm. Crosstalk of less than -26 dB was obtained even at 1.0 µm track pitch. In the overwrite cycle test using a 680 nm laser, no degradation of CNR up to 10000 cycles was observed.

TeSeF films by TeSe‐SeF6/Ar reactive sputtering for ablative optical recording

A TeSeF film with fine polycrystalline structure with a grain size of less than about 1000 A had desirable properties as a recording layer for an ablative write‐once medium. Low media noise, and uniform and regular pit shape were achieved. The TeSeF film was prepared by reactive sputtering of TeSe in a gaseous mixture of Ar and SeF6. The fluorine‐doping effect on the crystallinity of TeSe alloy films and a reactive sputtering process with TeSe alloy target in a gaseous mixture of SeF6 and Ar were studied. With SeF6 flow, polycrystalline films with a large grain size of more than a few thousand A became amorphous in an as‐deposited state. After annealing below 100 °C, the amorphous films became fine polycrystalline with a 500–1000 A grain size. This crystallinity change was due to 20–30 at. % of fluorine incorporating into TeSe networks in a hexagonal structure. Most of fluorine was unstable and evolved immediately during annealing even below 100 °C. But the residual a few at. % of fluorine was strongly in...

Adhesion between Te‐based alloy films and fluorocarbon sublayers during the ablative hole opening process

Adhesion between thin Te‐based alloy films and fluorocarbon polymer sublayers, prepared by sputtering or plasma polymerization, was investigated by observing the 1 μm‐sized ablative hole opening process with a focused laser beam. Interpretations of the mechanisms for the change in energy required for the hole opening and pit geometry were based on the framework of studies of the ablative hole opening process for optical recording. Observations suggest that the molten material flow during the hole opening includes a ductile fracture and a viscous flow of the molten sublayer material as well as of active layer material. Adhesion acts as an energy barrier against the above mentioned flow of molten material during the hole opening process. Since the fluorocarbon films used in the present work had highly cross‐linked structures, the adhesion was mainly dominated by the dynamic force of adhesion. Therefore, the hole opening process was mainly affected by the dynamic force of adhesion rather than the static forc...

New Write-One Optical Media Using Near Infrared Absorbing Metal Complex Dyes with Indoaniline-Type Ligand

Abstract New optical media have enough recording performance to be used as write once optical media: moreover these film show good light stability.

Dependence of Signals from Embossed Recording Fields and Grooves on Filling of Aperture of Objective Lens

The dependence of signals from embossed recording fields and grooves on the filling of the aperture of the objective lens was studied using a simulation based on a scalar diffraction method. The results indicated that this dependence is too large to ignore and consequently, the difference in the filling D/W between testers should be considered for the correlation between testers.

Minimum magnetic domain width of TbFeCo by magnetic field modulation recording

Stability of magnetic domains is evaluated on TbFeCo by measuring the minimum magnetic domain width (Wmin). Domains are recorded by magnetic field modulation method. Smaller Wmin can be observed by the sample with lower Tb content and higher sputtering pressure of under-layer. This can be explained by the temperature dependency of magnetization (Ms) and coercivity (Hc) qualitatively. From these results, we conclude TbFeCo has capability to record 0.1 micrometers .

Improvement of Magnetostatic Coupling in Reversal Magnetically Induced Superresolution.

Reversal magnetically induced super resolution (R-MSR) makes use of magnetostatic coupling, which is a very weak force, in contrast to exchange coupling. To avoid the disturbance by the unexpected external field during readout (H r ), methods for improving the magneto static coupling were studied. The direction of magnetization in the grooves markedly affected the H r dependence. When the grooves were erased in the direction antiparallel to that of lands, the H r stability showed symmetrical dependence on the direction of applied field. Moreover, adding a flux sink layer on the memory layer was effective for improving H r stability on long recording marks. This layer induced leakage flux from the center of the long recording mark. Consequently, the readout field stability of 170 Oe could be obtained with a 1.6 μm mark length.