T. H. Wu

Microstructure and recording mechanism of Ge∕Au bilayer media for write-once optical disc

The recording mechanism of Ge∕Au bilayer and its dynamic tests for write-once blue laser high density DVD (HD DVD) are investigated. It is found that Ge2Au3 phase is nucleated between amorphous Ge and crystalline Au layer after room temperature deposition. Crystallization of Ge∕Au interface layer at 170–190°C is induced by the nucleated Ge2Au3 sites at the interface, the bilayer structure is further heated to 200–450°C. After heating above 320°C, crystallized Ge are segregated at the grain boundary. The dynamic test results show that this Ge∕Au bilayer films can be applied to 1×–2× HD DVD-R.

Diffusion and crystallization mechanisms of Ge/Au bilayer media for write-once optical disk

Ge∕Au bilayer thin films were fabricated by magnetron sputtering method, the temperature dependence of resistance from room temperature to 500°C and concentration depth profiles are measured. From the temperature dependence of resistance measurement, we found two phase change phenomena which occurred at 175 and 360°C. The element concentration depth profiles of the as-deposited and recorded region indicate that the Au–Ge alloy is initially formed at the Ge∕Au interface. The dominant diffusion element is Au atom and the diffusion path is from Au layer to Ge layer. The optimum simulated bit error rate value is about 1.4×0−6 at 9.0mW under two time high definition digital versatile disk (HD DVD) recording speed. The dynamic tests show that this Ge∕Au bilayer films can be applied to one to two times HD DVD-R.

GeCu Thin Films for Inorganic Write-Once Media

The Ge100-xCux thin films (x=50 at.%-69 at.%) were deposited on nature oxidized Si (100) wafer by dc co-sputtering of Ge and Cu targets. Microstructures was analyzed by X-ray diffractometer. The optical and thermal properties were measured from static test. It was found that the as-deposited phase was single supersaturated epsiv-Cu3Ge phase and it was transformed to Ge and epsiv-Cu3Ge coexisting phases after annealing at 400degC. The reflectivity of as-deposited film was higher than that of annealed film

Effects of Mg doping and sintering temperature on the magnetoresistance of sintered Fe/sub 3/O/sub 4/ ferrites

In this paper, we improve MR value of the sintered Fe/sub 3/O/sub 4/ ferrite at room temperature, and microstructure on its magnetoresistance at room temperatures were investigated.

Optical properties of inorganic AgSb recording thin film

50nm Ag1−xSbx (x=10.8–25.5) thin films were prepared by magnetron sputtering. Thermal analysis shows that the phase change occurs around 250°C. The optical property analysis show that the as-deposited Ag80.9Sb19.1 films have high reflectivity of about 62%–73%. After heat treatment at 300°C, the contrast of Ag80.9Sb19.1 film is 12.5%–17% for wavelengths between 400 and 800nm. Dynamic test shows that using the Ag80.9Sb19.1 film as the memory layer of write once optical disk, a carrier-to-noise ratio of about 45dB can be achieved at λ=657nm, numerical aperture of 0.65, and a linear velocity of 3.5m∕s.

Ge/Al bilayer thin film for optical write-once media

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.

Effects of Pt content on the microstructure and magnetic properties of CoTbPt thin films

This work presents a single-layer CoTbPt film for use as a hybrid-recording medium. Co77.5−xTb22.5Ptx films with x=0–14 at. % are fabricated on glass and naturally oxidized silicon wafer substrates by dc magnetron sputtering. The magnetic film is sandwiched between SiNx protective layers to prevent oxidization. The effects of Pt content on the magnetic properties and microstructure of the film are investigated. X-ray diffraction and transmission electron microscope diffraction patterns revealed that all the films are amorphous. It shows that substituting a small amount of Co for the nonmagnetic element Pt will increase the saturation magnetization, the perpendicular remanence, and the perpendicular coercivity of the Co77.5Tb22.5 film. It is found that the saturation magnetization of the Co75.3Tb22.5Pt2.2 film is about 245 emu/cm3, the perpendicular squareness is about 0.8, perpendicular coercivity is about 2100 Oe at room temperature and the coercivity decreases rapidly with increasing temperature. The co...

Ge/sub 2/Sb/sub 2/Te/sub 5/ thin film doped with silver [optical disc storage]

The reflectivity and thermal properties are the main problems in GeSbTe phase-change disks that must be improved (N. Nobukuni et al., J. Appl. Phys. vol. 78, p. 6980, 1995; A. Hirotsune et al., Jpn. J. Appl. Phys. vol. 35, p. 346, 1996; C.M. Lee et al., J. Appl. Phys. vol. 89, p. 3290, 2001; S.Y. Kim et al., Jpn. J. Appl. Phys. vol. 38, p. 1713, 1997). We found that a small amount of Ag addition to the Ge/sub 2/Sb/sub 2/Te/sub 5/ film can increase the reflectivity, crystalline temperature, and the fcc to hcp phase-transition temperature. In addition, the activity energy of the amorphous to fcc phase transition was decreased.