Random Ag-SiN films consisting of random small Ag particles embedded in a SiN thin film were deposited by radiant-frequency magnetron sputtering. Specimens orderly comprising a random Ag-SiN film and an optical phase change recording layer were exposed to a focused laser beam. It showed that, with a random Ag-SiN layer deposited above the recording layer, the ablation of the recording layer occurred much faster and under much lower power than that of a single recording layer, which verified the local field enhancement of multiple scattering effects of the Ag particles. Finite Difference Time Domain (FDTD) calculation of a sandwiched structure consisting of ZnS-SiO2(130nm)/AgOx(20nm)/ZnS-SiO2(40nm) under a Gaussian beam irradiation has been carried out to simulate the near-field distribution in the structure. Near-field optical data storage adopting a Super-Resolution Near-field Structure (Super-RENS) usually utilizes similar films structure mentioned above to achieve super resolution storage density while getting a high Carrier to Noise Ratio (CNR) at the same time. Many recent works have reported that small Ag particles were formed in the AgOx film after converging laser irradiation onto the sandwiched structure. Here, another FDTD calculation was done to simulate the same model except for that small Ag particles were modeled in the AgOx film in the center region of the incident laser spot. The results showed a huge local near-field enhancement, which indicates that, if the structure full of such small Ag particles are formed in a tiny region beyond the optical diffraction limit, the optical recording and readout out density would be improved as well as a high CNR level achieved due to the multiple scattering of the Ag particles.
The optical properties of random Sb-SiN films in which Sb nano-particles are randomly dispersed were studied. Results show that the random Sb-SiN films possess high transmittance and low optical absorption. Additionally, some optical nonlinear phenomena of the random Sb-SiN films have been observed. Based on the special optical properties of random Sb-SiN films, they can be applied in many fields, for example, optical storage and optical microscopy. When the random Sb-SiN film was prepared close to a phase-change-recording layer, it decreases the threshold of input power for recording and speeds up the phase transition of recording media, and also improves the resolving power of readout system. On the other hand, while the random Sb-SiN films were deposited on the slide glass used in far-field optical microscopy, it obviously improves the resolving power of optical microscope and reduces the value of resolution limit to less than half of the value calculated by the expression given by Lord Rayleigh.
KEYWORDS: Thin films, Plasmons, Data storage, Scanning electron microscopy, Near field scanning optical microscopy, Near field, Transmittance, Optical switching, Germanium antimony tellurium, Near field optics
Nonlinear optical transimittance in the Super-RENS (super-resolution near-field structure) [glass/SiN(20nm)/ Sb(15nm) /SiN(20nm)] was investigated using a static transmittance measuring system with a focused laser illumination. The result shows an optical switching property with a strong nonlinear effect. Some SEM(Sanning Electron Microscope) images ofrecording spots in a PC(Phase Change) GeSbTe layer with and without the Super-RENS layers covering on it are presented. The images demonstrate the field enhancement effect due to the Super-RENS layers. The cause of the enhancement is considered as the local plasmon excitation.