Susumu Haratani

New Recordable Compact Disc with Inorganic Material, AgOx

A new recordable compact disc (CD-R) was formed with sputtered silver oxide, instead of organic dye. The optical and electrical properties were mostly equal to those of a CD-R with organic dye. The optical absorption of sputtered AgOx is uniform over a wide range of light wavelength, and more than 70% of the reflectance can be obtained at any laser wavelength applied by selecting the thickness of the dielectric film. It was found that the recording principle mostly depends on the explosion pressure of released oxygen from AgOx due to the laser power of recording.

In-Ag-Te-Sb phase change recording media at compact disk linear velocity

The feasibility of In-Ag-Te-Sb phase change recording media was investigated at an actual compact disk (CD) linear velocity. The composition of 0.5 at% V-doped In3.8Ag12.4Te28.8Sb55.0 was used for the recording layer which we have reported previously. To improve the repetition property of overwriting, the disk structure was modified so that the cooling rate of the disk was increased. Consequently, recording jitter of less than 30 ns and modulation of more than 60% were maintained up to 2000 repetitions of overwriting when eight-fourteen modulation (EFM) signal with pulse-train division was applied.

Micromagnetic simulations of polycrystalline cobalt islands for patterned media

The magnetization state and the switching field of single domain polycrystalline islands (40 nm/spl times/80 nm/spl times/10 nm) were investigated by micromagnetic simulations. In this work, the crystalline orientations of the grains forming the islands were randomly chosen from a Gaussian distribution, centered along the in-plane short axis of the island. The remanent magnetization was shown to be parallel to the in-plane short axis when the standard deviation /spl sigma/ of the distribution is below 30 degrees. The highest coercivity of an assembly of 100 individual islands was found to be between 3100 and 3700 Oe when /spl sigma/ is as low as 10 degrees and the islands comprise 512 grains. Such an array is promising as recording media for densities beyond 100 Gb/in/sup 2/.

Property change of AgOx recordable compact disk with various dielectric films

A recordable compact disk media with an inorganic material, AgOx, is reported. A scanning tunneling microscope image of a polycarbonate substrate of this media after recording was measured and the pit shapes of the image were evaluated. It was found that there existed a linear correlation between the pit shapes and the cross‐talk value with a coefficient of 0.959, and the mechanism of the pit formation was proposed by the scanning tunneling microscope image. The optical and electrical property changes were investigated by use of different dielectric thin films, SiO2, SiN, LaSiON, and SiNO. A cross‐talk value of a disk using a SiNO film was improved to mostly satisfy the compact disk standard. The property changes can be explained by the proposed pit formation model.

V and Ti Doping Effect on In-Ag-Te-Sb Optical Phase Change Rewritable Disc

In-Ag-Te-Sb is known as one of the alloys suitable for optical phase change recording, which has a high erasability at the linear recording velocity of around 7 m/s. The phase change rewritable recording succeeded at the linear recording velocity of 1.4 m/s with 0.5 at.% doping of Ti or V atoms, which delayed the crystallization time drastically, but maintained the high erasability. It was possible to make 103 repetition recordings with jitter in the reproduced signal of less than 40 ns, when the eight-fourteen modulation (EFM) signal, which is generally used for compact discs (CD), was applied.

Micromagnetic modeling of discrete patterned perpendicular media

In this paper, the benefit to separate each track and the feasibility to increase track density are investigated by using Landau-Lifshits-Gilbert micromagnetic model. A MFM image of the discrete patterned media recorded at 50 kFCL is shown. In the recording process, the single pole write head with a width, Pw, of 200 nm and a thickness, Pt, of 300 nm is used.

Scanning Tunneling Microscopy Image of GeSb2Te4 Thin Films

A scanning tunneling microscopy image of thin film sputtered by a GeSb2Te4 target was obtained in oil conditions. The phase change of the films was confirmed from STM images when the films were heated at 250°C for 2 and 4 minutes. The arrangement of the atoms constituting the surface of the films was inferred through the consideration of the topographic image height with each different work function of the atoms.