Super-resolution near-field disk with phase-change Sn-Doped GeSbTe mask layer

A new mask layer of Sn-doped (7 at. %) Ge₂Sb₂Te ₅ was developed and used on super-resolution near-field phase-change optical disks (super-RENS). Temperature-dependent reflectivity result showed a reflectivity change at 169 °C with Sn doping into Ge₂Sb ₂Te₅. The mask material also showed high thermal stability. Optical study indicated the suitability of the film for use in blue-laser recording and as a mask layer. Fast crystallization within 90 ns was achieved using a pulsed high-power laser beam of 405nm wavelength. Dynamic recording performance of the new structure showed carrier-to-noise ratios (CNR) of 37 and 18 dB obtained for 80 and 50nm mark sizes, respectively. Readout thermal stability of 12,000 cycles was realized for 80nm mark sizes. The incorporation of Sn-doped GeSbTe (GST) as mask layer in the super-RENS structure significantly improved the CNR and thermal stability of the disk.