Chalcogenide thin films for laser‐beam recordings by thermal creation of holes

摘要

The shapes of holes thermally created by a laser beam in thin films of wide range of materials are studied. The most cleanly shaped holes, which measure up to recent requirements for direct‐read‐after‐write video recordings by submicron dots, are obtained in some compositions of amorphous chalcogenide thin films such as As‐Te system, Ge‐Te system, As‐Se system, Ge‐Se system, and Sb‐S system thin films. The experiments clarify several important conditions helpful in obtaining cleanly shaped holes. The most important condition is that the viscosity of the material in liquid or softened state should be high. The required incident laser‐beam power for recording in an As‐Te system thin film on a polymethyl methacrylate substrate rotating at 1800 min-1 is about 10 mW. Addition of Se to the As‐Te system thin films greatly increases film stability. A signal‐to‐noise ratio of about 45 dB is obtained in reproduced color video signals.