Masaetsu Takahashi

Completely Erasable Phase Change Optical Disc II: Application of Ag–In–Sb–Te Mixed-Phase System for Rewritable Compact Disc Compatible with CD-Velocity and Double CD-Velocity

Aiming to obtain a rewritable compact disc (CD-rewritable) with high performance at both CD-velocity (CD1X) and double CD-velocity (CD2X), the phase change optical disc with the Ag-In-Sb-Te system has been developed. In the one-pass overwriting mode with eight-to-fourteen modulation, high carrier-to-noise ratio, wide power margin and high erase ratio have been obtained at both velocities. As for stability, we acquired a satisfactory result in the read-out test of 106 cycles with read power of 1.5 mW. We conclude that the phase change optical disc with the Ag-In-Sb-Te system is suitable for use at both CD1X and CD2X. Furthermore, the phase change process of the Ag-In-Sb-Te system has also been investigated. The chemical structure of the Ag-In-Sb-Te system in its ordered state was found to be (Ag-Sb-Te)x(In1-ySby)1-x.

SrSe:Ce Thin Film Electroluminescent Device

The emission spectra corresponding to 5d-4f transition of Ce3+ ion vary with the host material [1], Ce3+ ion is considered to be one of the useful emitting centers for multi-color electroluminescence (EL). Recently, SrS:Ce and CaS:Ce thin film EL (TFEL) devices have attracted much attention because of their brightness [2, 3], As compared with the emission spectra of CaS:Ce devices, these of SrS:Ce devices shift to shorter wavelength by about 30 nm, and consequently exhibit blue EL. This fluctuation on the emission spectra is explained as follows; The 5d excited state of Ce3+ ion is very sensitive to the crystal field because the 5d state is not shielded by the 5s2p6 closed shells [4, 5]. However, the EL colors of SrS:Ce devices are not sufficient for the primary blue. We have been carrying out the attempts to replace SrS by SrSe [6]. In this paper, the characteristics of the SrSe:Ce TFEL devices are reported with the emphasis on EL spectra.