Silver oxide layers were prepared by reactive r.f. magnetron sputtering of a silver target in oxygen containing atmosphere. Spectroscopic analysis of the films revealed a gradually composition change from Ag over Ag2O to AgO with increasing oxygen addition. Raman spectroscopy in combination with optical transmission measurements indicated that the AgOx constituents readily decompose by laser irradiation to optically active silver scattering centers and oxygen. Surface enhanced Raman scattering (SERS) of carbon traces in the silver oxide layers verified the potential to excite local surface plasmons in such silver aggregates. Furthermore, SERS activity of the activated layers is demonstrated by the clear amplification of Raman bands of low concentrated chemicals. The example of the model molecule benzoic acid (BA) applied to AgO films on glass substrates allows to observe the activation process in situ. SER characteristics were found to be dependent on the silver oxide film constitution and the state of intermediate silver cluster formation along with the applied photoactivation-time and power.
Readout characteristics of light-scattering-mode super- resolution near-field structure (super-RENS) disks are described in detail. Readout intensities in reflected and transmitted signals are compared. Both signals showed mostly the same carrier-to-noise ratios (CNRs) using objective lenses with NA of 0.6. The formation mechanism of light scattering centers in the super-RENS disks ia also described in comparison with several different disks. As increasing oxygen ratio during the deposition of silver oxide (AgOx) layers, two different chemical reactions were identified. It was found that the super-RENS disks with oxygen-rich AgOx films have both characteristics of transparent and light- scattering apertures in one disk. Further study also revealed that the AgOx dynamic nonlinearity is not so high and less than 6% by the film itself; however, it is enhanced to 12% in super-RENS. It is supposed that the imaginary refractive index k of the films is less than 0.1; therefore, it is hard to heat itself to the decomposition temperature without a heat source (GeSbTe film) underneath. This result would be a hint to further increase CNRs in a light- scattering-mode super-RENS disks.
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