Wei-Chih Hsu

Oxygen and Nitrogen Co-Doped GeSbTe Thin Films for Phase-Change Optical Recording

Nitrogen and oxygen co-doped GeSbTe films for phase-change optical recording are investigated. It is found that optical properties of amorphous and crystalline state are similar to that of GeSbTe, crystallization temperature increases and crystalline microstructure is refined which indicate a nucleation rate increases by co-doping. The carrier-to-noise ratio (CNR) and erasability of phase-change optical disks are improved being up to 52 dB and 35 dB, respectively, by using an appropriate co-doping concentration in the recording layer.

Blue-Laser Readout Properties of Super Resolution Near Field Structure Disc with Inorganic Write-Once Recording Layer

A novel inorganic write-once recording material SbNx (antimony nitride) was proposed for super resolution near field structure (super-RENS) discs. The layer structure is polycarbonate substrate (0.6 mm)/ZnS–SiO2 (170 nm)/AgOx (15 nm)/ZnS–SiO2 (40 nm)/SbNx (25 nm)/Ag (100 nm)/UV-curing resin/dummy PC substrate (0.6 mm). The recording layer with high-contrast characteristics enhanced the readout signal, which was compared with that of conventional phase-change materials. The carrier-to-noise ratio (CNR) of 150 nm mark length was about 44.2 dB at a readout power of 2.5 mW using blue laser. A below-diffraction-limited mark length as short as 60 nm can be readout using blue laser of 405 nm with a lens having a numerical aperture of 0.65.

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

Z-Scan Study of Nonlinear Optical Coupling of PtOx and Ge2Sb2Te5 of Near-Field Optical Recording Structure

The strong local nonlinear optical coupling properties of a 5 nm PtOx thin film sandwiched by two Ge2Sb2Te5 phase-change structures of a new type super-resolution near-field optical disk are investigated and observed by Z-scan experiments.

Thermal and Optical Properties of Organic Dyes for Super-Resolution Recordable Disks

We have studied the characteristics of super resolution optical disks with an organic dye used for the recording layer. It was demonstrated that cyanine dyes with either high decomposition temperature or low absorption show good readout durability and high carrier-to-noise ratio (CNR).

GaGeSb alloys for high-speed reversible phase-change optical recording

New Ga doped GeSb based phase-change materials are investigated. These materials possess good optical contrast at short wavelengths. Crystallization temperature increasing and grain size refinement are obtained by addition of Ga. More than 50 dB CNR and 25 dB erasability are measured in disks with simple four layer stacks using blue laser and linear velocities 7 m/s and 10.5 m/s.

Nonlinear optical properties of the Au-SiO2 nanocomposite superresolution near-field thin film

A Au-SiO2 superresolution nanocomposite active nonlinear optical thin film is fabricated reproducibly by cosputtering method with the size of Au nano particles around 2 to 10 nm. Results of the Z-scan indicate that these nanocomposite Au-SiO2 films have nonlinear optical properties and enhanced transmittance at the focusing position. For a 15-nm-thick Au-SiO2 nanocomposite thin film, the transmittance can be 135% for a sample with an average grain size of around 5 nm.

Super-resolution recordable disc with organic dye for recording layer

A new structure of super resolution optical disk with organic dye for recording layer was proposed. By utilizing of Sb thin film for the mask layer, below-diffraction-limited marks on organic recording layer could be recorded and retrieved. The mark size as small as 120nm could be read out on the current dynamic tester of digital versatile recordable disc (DVD-R). The conditions of optical pickup head are 635nm of laser wavelength (l) and 0.6 of lens numerical aperture (NA). The carrier-to-noise ratio (CNR) from recorded marks of 200nm was more than 28.5dB at low readout power of 2mW and at a constant linear velocity (CLV) equals 3.5 m/s. The recording layer with modified composition owned high thermal stability and the readout durability was more than 6 X 104 cycles without any decreasing of CNR.

Z-scan nonlinear optical properties of the Au-SiO 2 nanocomposite thin film

Au-SiO2 nanocomposite thin film is fabricated reproducibly by co-sputtering method with the size of Au nano particles around 2 to 10 nm. TEM images display the irregular shape Au nanoparticles are embedded in SiO2 thin film with random distribution. A surface plasmon absorption peak of Au nanoparticles is found in absorption spectra. The nonlinear optical properties are measured by confocal Z-scan method with a sub-nanosecond pulse laser (λ=532nm, pulse width 0.71ns, repetition rate 15.79kHz) and high-numerical-aperture objective lens (NA=0.55). Results of the Z-scan show nonlinear optical properties and enhanced transmittance at the focusing position of nanocomposite Au-SiO2 films. The transmittance can be more than 135% for a 15-nm-thick Au-SiO2 nanocomposite thin film with an average grain size of around 5 nm.

Z-Scan Study of Nonlinear Optical Coupling of PtO x and Ge 2 Sb 2 Te 5 of the Near-Field Optical Recording Structure

Strong local nonlinear optical coupling properties of a sandwiched 5 nm PtOx thin film by two sandwiched Ge2Sb2Te5 phase-change structures of a new type super-resolution near-field optical disk are investigated and observed by Z-scan experiments.