Ge/Al bilayer thin films are prepared by magnetron sputtering. Thermal analysis shows that the phase change of the film occurs at 275 °C. Contrasts at 650 nm and 405 nm wavelength are 71.4% and 31.1% respectively.
The approach to increase optical recording density has become very popular research subject in these years. One direct and effective method is to increase the recording layer stack number. That is to say, to add one more recording layer can get one more recording capacity.
In this paper, we will propose a new method for manufacturing read only type multi-layered disc. The process is described in the following. This first recorded data layer (called L0) still follows the traditional DVD disc manufacturing process. We obtain the polycarbonate substrate by replicating from Ni stamper. Then polycarbonate substrate is sputtered thin silicon film for semi-reflection layer. As for second layer (L1) and even more layer (Ln-1) producing, one special kind of duplication (called SKD) method is proposed. The duplication (or replication) source of second or nth recorded data is not only limited from Ni stamper. Even polycarbonate or PMMA substrate has recording data are also acceptable sources. At next step, the duplication source is deposited by thin gold film. Then we apply spin coating to bond the first layer (L0) substrate and second layer (L1) duplication source by choosing suitable UV curing glue. After being emitted by UV lamp for several seconds, we can easily separate the duplication source of second layer (L1) from (L0) substrate. Then we find the thin second data layer (L1) is replicated and stacks upon the first layer. On the same way, we sputter thin AgTi layer on the thin second data layer for another semi- reflective layer. By following the above manufacture step, we can produce more layers.
In our experimental, we prepare triple layered read-only type disc. The total capacity is almost 12GB for one side of disc, and 24GB for two side of disc. The read-out intensity of laser from each data layer is expected to be similar. Thus we have designed particular reflectance and transmittance for each data layer by controlling the thickness of thin silicon film. We can verify our design by checking the focusing error signal in S-curve search of optical pickup head. The signal quality for each layer can be found from the signal eye pattern and jitter. For compatibility with present drive system, the requirement of the readout signal from each layer should be same as DVD or CD specification
The rare earth-transition metal (RE-TM) alloys are widely accepted as the most suitable material for magneto-optical (MO) recording. The magnetic and optical properties of the recording media, hence the read-write-erase characteristics of the disk, are crucially dependent on the composition of the RE-TM films. Tailoring the composition of the films to meet the requirements in various magneto-optical recording applications is, therefore, important. In-line sputtering is the most common method for RE-TM film coating in disk production process. There are two common methods for fabricating sputter target; one is powder-sintering, the other is melt-casting. The former method yields a target composed of mixtures of pure element phases and certain percentage of intermetallic compound phases, the latter method yields a target composed of 100% intermetallic compound phases. The sputtering of RE-TM target often gives nonuniform composition distribution on the disk based on past experiences. This problem motivated us to study the sputtered atom distribution of the targets which were fabricated by different methods.
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