US Patent 7541081 Phase change memory for archival data storage

A structure for storing digital data is provided, with a high reflectance layer comprising a noble metal formed over an underlying material layer, and a plurality of low reflectance portions comprising a mixture of a noble metal and an underlying material. The plurality of low reflectance portions have top surfaces comprising a compound of the underlying and the noble metal. A method of changing reflectance on a data storage disk is also disclosed. The method comprises the acts of irradiating a laser light beam onto a noble metal formed over an underlying layer, and raising the temperature of the noble metal above the melting temperature forming a compound of the noble metal and the underlying material.