<title>Phase-change material for use in rewritable dual-layer optical disk</title>

Abstract

A thin film of Sn-doped and GeTe-rich GeTe-Sb<SUB>2</SUB>Te<SUB>3</SUB> shows characteristics that make it suitable for use in rewritable dual-layer optical disks employing a violet laser. By increasing the GeTe component form Ge<SUB>2</SUB>Sb<SUB>2</SUB>Te<SUB>5</SUB> to Ge<SUB>4</SUB>Sb<SUB>2</SUB>Te<SUB>7</SUB>, and Ge<SUB>8</SUB>Sb<SUB>2</SUB>Te<SUB>11</SUB>, optical changes were increased. By substituting Sn for a proposition of Ge in these compositions, crystallization rates are greatly increased and even a 5 nm-thick film showed a very short laser-crystallization time of less than 50 ns. The material film was successfully applied to Layer 0 of rewritable dual-layer disk: capacity of 27 GB and a 33 Mbps data transfer rate were confirmed for a disk using a conventional 0.6 mm substrate, and 45 GB capacity and the same data transfer rate were obtained for another disk using thin cover layer 0.1 mm thick.