High-Density Read-Only Memory Disc with Super Resolution Reflective Layer

We report that super-resolutional readout occurred in read-only memory (ROM) discs with very simple materials and structure. By adopting a 15-nm-thick layer of Ge, Si, Mo, and W as a reflective layer, a carrier-to-noise ratio over 40 dB could be obtained from small pits which were below the resolution limit of our optical system. Experimental and thermal simulation results showed that the super resolutional readout phenomenon in the discs is strongly correlated to the film temperatures that are reached when a laser spot is irradiated on the films. Signal characterizations suggest that the super resolutional readout mechanism of the discs is different from those of conventional ROM and conventional super-resolutional ROM discs. We have named them “Super-ROM” discs.