Junji Tominaga

STRUCTURE OF THE OPTICAL PHASE CHANGE MEMORY ALLOY, AG-V-IN-SB-TE, DETERMINED BY OPTICAL SPECTROSCOPY AND ELECTRON DIFFRACTION

The structure of the optical phase change memory alloy, silver–vanadium–indium–antimony–tellurium (AVIST), has been investigated by the methods of optical reflectivity change, Raman spectroscopy, and electron diffraction. In order to identify each phase, Sb, AgSb, AgSbTe, and AgInTe films were also studied. The Raman spectrum of an AVIST thin film annealed at 523 K for 1 h in Ar gas, shows two main broad peaks around 116 and 150 cm−1. These peaks appear to be related to Sb vibration modes in the AVIST alloy, but their relative intensities are reversed for the AVIST films in comparison with those for a Sb film. Furthermore, in AVIST, the peak at 116 cm−1 shifts to lower wave number when the vanadium content is increased from 0.4 to 4.7 at %. The electron diffraction pattern of AVIST alloy indicates that the AgSbTe2 crystalline phase dominates rather than Sb. A model of the structure of AVIST consistent with these observations is proposed.

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.