Real-Time Write Strategy Optimization Method for Optical Discs

Abstract

The structural and optical properties of GaN epilayers grown on intentionally strained sapphire (0001) substrates by metalorganic chemical vapor deposition (MOCVD) were investigated. Intentionally tensile strained sapphire substrates were prepared by the implantation of 2.4 MeV energy Cl þ and As þ -ions with a 10 15 cm À2 dose where the projection ranges (R p ) were 1.16 mm and 0.95 mm, respectively. It was found from Raman spectroscopy that the compressive stress normally existed in the GaN epilayer/sapphire was decreased by the use of a Cl þ -ion-implanted sapphire substrate. The intentionally tensile strained sapphire surface can result in a superior crystalline GaN epilayer on top of it. However, excessively roughened and modified surface by As þ -ions degraded the GaN epilayer. Not only the ionic radius but also the chemical species of implanted ions in sapphire affected the crystal quality of GaN epilayers. Therefore, we concluded that the properly tensile-strained sapphire (0001) substrate could improve the properties of GaN epilayers grown by MOCVD.

Simplified Transfer Function of Write Compensation for Phase-Change Optical Disks

“…Several write compensation methods have been proposed for the mark formation of phase-change optical disks experimentally. [6][7][8][9][10][11][12][13][14][15][16] These studies could deal with the recording process of the phase-change optical disk using realistic methods; however, they did not directly give the relationship between write compensation and thermal characteristics in an arbitrary phase-change optical disk. The dynamic temperature distribution in an optical disk when an optical beam passed over the optical disk was studied analytically and numerically.…”