Structural phase transition of AgOx sandwiched between ZnS-SiO2 protective layers under thermal and laser pulse annealing for super-resolution near-field recording

The as-deposited AgOx prepared at an oxygen flow ratio of 0.5 consisted of Ag2O and AgO phases. During thermal annealing, the reduction of AgO into Ag2O, decomposition of Ag2O into Ag and O2, and out diffusion and aggregation of decomposed Ag would take place successively. The chemical decomposition of AgOx film sandwiched between two ZnS-SiO2 protective layers was confirmed to be an irreversible process. As being irradiated by a high power laser pulse similar to the recording process, a hollow Ag cylinder, or ring, serving as an aperture, was formed in the AgOx mask layer, and small Ag particles, serving as light-scattering centers, were precipitated in the center region. During the readout process, the small aperture can significantly reduce the readout laser spot size, while the strong near-field interaction between precipitated Ag particles and sub-wavelength marks can effectively enhance the readout signal. That elucidates the recording and readout mechanisms of super-resolution near-field structure disk with an AgOx mask layer.