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5.4 Future Applications 211
(a) (b)

Initialization
Mask
(AgO ) Ag particle
x
Protective
Recording As-depo Initialization (P = 3.5 mW)
(GeSbTe) i
(c) (d) (e)

Ag cluster Ag diffusion Ag ring

= 4.0-5.0 mW P = 5.5-7.5 mW : greater than 8.0 mW
P w w P w
Fig. 5.58. Proposed working mechanism of super-RENS using AgO mask layer
x

P r = 6 mW in the spectrum in the upper right figure and the signal amplitude
decreases due to the degradation of the resolution (Ag cluster size increases).

Scattered type super-RENS working mechanism
On the basis of these results, we propose a model for an Ag-super-RENS mech-
anism. Figure 5.58 shows the states just after writing (P r = 1 mW) for both
the mask layer and the recordinglayer, with write power P w as a parameter.
The workingmechanism for the Ag-super-RENS is as follows. Both the mask
and the recordinglayer have five possible states dependingon the write power
P w (a) as-depo, (b) Agparticles uniformly dispersed and crystallized (after
initialization P w =3.5 mW), (c) Agcluster and half amorphous (P w =4–
5 mW), (d) Agdiffusion and completely amorphous (P w =5.5–7.5 mW), and
(e) Agringand bubble pit (greater than P w = 8 mW). The mask layer for the
super-RENS readout (P r = 4 mW) has an Agringstructure, and the aperture
is filled with O 2 , which increases both the CNR and the resolution limit.
Optical pulse duty dependence

To realize a short mark length, we illuminated thermally isolated optical pulses
(havingdecreased duty ratio). Figure 5.59 shows the relationship between re-
flectivity V 1 (non-mark), V 2 (mark), and mark length for the write power of
P w =8.5 mW with the super-RENS readout (P r = 4 mW); the optical pulse
duty ratio as a parameter. The signal amplitude V pp = V 1 − V 2 increases as
the duty ratio decreases, which means the amorphous level difference between
mark and nonmark increases because the difference in temperature increases
due to the longer time separation between the laser pulses. Figure 5.60 shows
the relationship between CNR and mark length for the super-RENS readout,
optical pulse duty ratio as a parameter (P w =8.5 mW). The reproduced signal