• Journal of the Korean institute of surface engineering
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• v.37 no.4
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• pp.196-199
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• 2004

Seedlayers with low surface energy which increases the density of nucleation sites in the initial growth region of the recording layer deposited on them was studied to reduce grain size in recording layer. The seedlayer with low surface energy was so effective to attain finer grain in magnetic upper-layers. The Ni-Fe-O intermediate layer with low surface energy was found to be effective in reduction of grain size as well as magnetic cluster size of Co-Cr-Ta-Pt recording layer. Furthermore, the reduction of grain size in Co-Cr-Ta-Pt recording layer on Ni-Fe-O intermediate layer with low surface energy led to decrease the noise level in the high recording density region.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.7
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• pp.793-796
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• 2004

In order to improve c-axis crystalline orientation and high perpendicular coercivity of deposited ${Co}_77{Cr}_20{Ta}_3$perpendicualr recording layer, Two step method was investigated using a Facing Targets Sputtering System(FTS). The ${\Delta\theta}_50$ of ${Co}_77{Cr}_20{Ta}_3$recording layer deposited on seedlayer prepared at Room Temperature was as low as $5^\circ$, while that of the recording layer without seedlayer was about 11$^{\circ}$. The Two-Step method using ${Co}_77{Cr}_20{Ta}_3$seedlayer prepared at Room Temperature was shown to be very effective in controling the c-axis orientation of ${Co}_77{Cr}_20{Ta}_3$ recording layer with thin thickness.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.589-595
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• 2001

The present study conducted heat transfer analysis in multi-layer of CD-R. It is necessary to analyze heat transfer during the recording process to find optimum power and write strategy in CD-R. This study investigated effects of several parameters such as recording speed, laser power, layer thickness and thermal property. The calculated results presented temperature distribution in the multi-layer and detailed information of recording characteristics. Optimum laser power was estimated, comparing an optimum mark length with the calculated mark lengths. The results showed that the optimum laser power was influenced significantly by the layer thickness and the thermal properties of the dye.

• Transactions of the Society of Information Storage Systems
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• v.1 no.1
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• pp.34-41
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• 2005

We report some recent results in the rewritable Blu-ray Disc with enhanced overwrite cyclability by using the growth dominant eutectic based Ge(Sb70Te30)+Sb recording layer, GeN interface layer and write strategy optimization. We have developed phase-change optical media with appropriate write strategy for 36(i.e., 1X)-72Mbps(i.e., 2X) dual speed Blu-ray Disc system and fur the future high speed optical data storage. For recording layer, eutectic-based Ge(Sb70Te30)+Sb material was used and Sb/Te ratio and Ge content were optimized to obtain proper erasability and archival stability of recorded amorphous marks. The recording layer is wrapped up in GeN interface layers to obtain overwrite cyclability and higher crystallization speed. In addition, we designed appropriate write strategy so called Time-Shifted Multipulse (TSMP) write strategy where starting position of multipulse parts are shined from reference clock. With this write strategy, the jitter characteristics of the disc was improved and we found that leading edge jitter was improved much more than trailing edge jitter in 1X-2X speed recording. Finally, we investigated the higher speed feasibility of 144Mbps(i.e., 4X) by adopting some elemental doping to the eutectic based Ag-In-Sb-Te recording layer and structural optimization of constitution layers in Blu-ray Disc. In the paper, we report the effect of Sn addition for the feasibility of higher speed recording. The addition of Sn shows increases of the crystallization speed of phase change recording layer.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11a
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• pp.77-80
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• 2001

Crystallographic and magnetic characteristics of CoCr-based magnetic thin film for perpendicular magnetic recording media were influenced on preparing conditions. In these, there is that substrate temperature was parameter that increases perpendicular coercivity of CoCrTa magnetic layer using recording layer. While preparation of CoCr-based doublelayer, by optimizing substrate temperature, we expect to increase perpendicular anisotropy of CoCr magnetic layer and prepare ferromagnetic recording layer with a good quality by epitaxial growth. CoCrTa/Si doublelayer showed a good dispersion angle of c-axis orientation $\Delta$$\theta$$_{50}$ caused by inserting amorphous Si underlayer which prepared at underlayer substrate temperature 250C. Perpendicular coercivity was constant, in-plane coercivity was controlled a low value about 2000e. This result implied that Si underlayer could restrain growth of initial layer of CoCrTa thin film, which showed bad magnetic properties effectively without participating magnetization patterns of magnetic layer. In case of CoCrTa/Si that prepared with ultra thin underlayer, crystalline orientation of CoCrTa was improved rather underlayer thickness 1nm, it was expected that amorphous Si layer played a important role in not only underlayer but also seed layer.t also seed layer.r.

• Journal of the Korean Magnetics Society
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• v.4 no.1
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• pp.20-24
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• 1994

The read/write characteristics of CoCr/NiFe double layered media are strongly affected by the magnetic properties of NiFe magnetic soft layer as well as those of CoCr recording layer. Modification of the permalloy layer by NiFe/Ge multilayer scheme resulted in the higher recording sensitivity and the higher reproduced voltage of CoCr/NiFe medium and this is attributed to the higher permeability of the back layer and high perpendicular anisotropy of the CoCr recording layer. Although higher permeability of back layer results in higher recording sensitivity, the increment of the reproduced voltage was not remarkable, which can be confirmed in the FEM numerical analysis. On the contrary, peak shift characteristics of the CoCr/NiFe medium with the NiFe multi back layer was deteriorated compared to that of the CoCr/NiFe medium with NiFe single back layer. Insertion of ferromagnetic thin CoZrNb intermediate layer between CoCr and NiFe layer was effective to ensure large reproduced voltage and low peak shift. These recoridng characteristics were also discussed in connection with microstructural characteristics.

• Electrical & Electronic Materials
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• v.8 no.1
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• pp.64-70
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• 1995

We discussed the thermal analysis for a recording media with the variation of the laser pulse duration, the laser power and the temperature distribution in order to optimize the Te-based antireflection structure from the computer calculations. In the case that the radial heat diffusion is negligible, we can calculate the maximum temperature of the recording layer at the center of the spot by the Simple Model. The temperature profile of the recording layer is obtained from the Numerical Model by considering the total specific heat and the latent heat. As a result, the effect of the heat sinking acting as a thermal loss for the hole formation could be minimized by introducing the pulse with the hole formation duration(.tau.) below the thermal time constant(.tau.$_{D}$) of a dielectric layer. These requirments can be satisfied by using the dielectric thickness of the 2nd ART(Anti-Reflection Trilayer) condition or the dielectric materials with a low thermal diffusivity.y.

• Transactions of the Society of Information Storage Systems
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• v.2 no.4
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• pp.219-223
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• 2006

Near field recording(NFR) technology has been considered as a strong candidate to surpass the far-field diffraction limit imposed by the nature of light in present optical disk drives such as CD, DVD, and BD(Blu-ray Disk). In this paper, we suggest novel inside near-field dual layer recording concept using elliptic shape solid immersion lens(ESIL).

• Macromolecular Research
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• v.9 no.6
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• pp.313-318
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• 2001

The present study relates to a method of manufacturing 100$\mu\textrm{m}$ thick cover layer for the high density digital versatile disc system (HD-DVD), which uses a high numerical aperture of 0.85 at 405 nm wavelength. Spin coating technique was investigated as means for manufacturing the cover layer within sufficient margins of thickness variation and with good mechanical properties including small radial and tangential tilts. The influence of processing variables such as spinning speed, spinning time, and dispensing position was investigated. The effect of viscosity of UV-curable resin was also investigated.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.463-465
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• 2002

In order to increase perpendicular magnetic anisotropy of magnetic layer and prepare magnetic recording layer with a good quality by epitaxial growth between magnetic layer and, we prepared Co$\_$77/Cr$\_$20/Ta$_3$/Si doublelayer for perpendicular magnetic recording media which was promoted as next generation recording media on slide glass substrate. The thickness of magnetic layer and Underlayer were varied from 20 to 100 nm and 5 to 100 m, respectively. The surface morphology and crystal structure of the CoCrTa/Si film were examined with XRD and AFM. Prepared thin films showed improvement of dispersion angle of c-axis orientation Δ$\theta$$\_$50/ caused by inserting amorphous Si underlayer.