Shinkichi Horigome

Chalcogenide thin films for laser‐beam recordings by thermal creation of holes

The shapes of holes thermally created by a laser beam in thin films of wide range of materials are studied. The most cleanly shaped holes, which measure up to recent requirements for direct‐read‐after‐write video recordings by submicron dots, are obtained in some compositions of amorphous chalcogenide thin films such as As‐Te system, Ge‐Te system, As‐Se system, Ge‐Se system, and Sb‐S system thin films. The experiments clarify several important conditions helpful in obtaining cleanly shaped holes. The most important condition is that the viscosity of the material in liquid or softened state should be high. The required incident laser‐beam power for recording in an As‐Te system thin film on a polymethyl methacrylate substrate rotating at 1800 min−1 is about 10 mW. Addition of Se to the As‐Te system thin films greatly increases film stability. A signal‐to‐noise ratio of about 45 dB is obtained in reproduced color video signals.

Infrared Spectra of Amorphous Silicon-Fluorine Alloys Prepared by Sputtering in Fluorosilane-Argon Gas Mixture

Infrared spectra of amorphous Si : F alloys prepared by sputtering of a silicon crystal in SiF4 or a mixture of SiF4+Ar were measured in the frequency range of 450–4000 cm-1. Six absorption bands were observed in the 800–1100 cm-1 region. These bands are assigned as the SiFN (N=1, 2, 3) bond stretching vibration modes by comparison with the infrared spectra of SiFNH4-N molecules. In addition, fluorine modified or enhanced Si-Si bond stretching modes were observed at 515 and 650 cm-1.

Single‐beam overwrite experiment using In‐Se based phase‐change optical media

Single‐beam overwrite in an optical disk is reported using In‐Se‐Tl amorphous‐crystalline phase‐change recording films having very short erasing (crystallization) time of 0.2 μs. The lifetime of the amorphous state in an In‐Se‐Tl film is estimated to be longer than 10 years at 60 °C. This is due to its high crystallization temperature (135 °C) and high activation energy (2.6 eV). The phase‐change cycles can continue over 106 cycles in stationary state experiments using test samples. The possibility of single beam overwrite (rewriting without prior erasing as with a magnetic disk) is verified by using a 1.6‐μm‐diam round laser beam spot irradiated on a 5‐in.‐diam disk rotating at 2400 rpm.

PGMA as a High Resolution, High Sensitivity Negative Electron Beam Resist

High resolution and high electron beam sensitivity are found in poly (glycidyl methacrylate) (PGMA). PGMA resists with sensitivities in the 1×10-7 to 5×10-6 C/cm2 range and γ-values in the 1.8 to 2.7 range are easily obtained using solution polymerization and fractional precipitation. The γ-value increases with decreasing polydispersity (Mw/Mn), and γ>1.8 is obtained when Mw/Mn<1.4. A resist pattern of lines 0.2 µm wide with 0.24 µm spacings is obtained on a silicon wafers. This resist is useful for pattern fabrication of chromium, silicon dioxide, and polycrystalline silicon layers.

Optical Digital Data Storage Technologies With Semiconductor Laser Nead

A laboratory model optical disk file memory for digital data storage is developed. User storage capacity is 2GBytes per disk and data transfer rate is 350KBytes/sec. Average seek time is 150msec. Several new technologies supporting the device are also described in detail.

In-Se Based Phase Change Reversible Optical Recording Film

In-Se based amorphous-crystalline phase change recording films are analysed in terms of structure, optical properties, crystallization speed, and crystallization activation energy. Crystallization by a laser beam is possible by a 0.2μs pulse. Crystallization temperature(heating rate 5°/C min.) measured by using a differential scanning calorimeter is 135°C and crystallization activation energy is calculated to be 2.6eV. The life of the amorphous state is estimated6 to be longer than 10 years at 60°C. The phase change cycles can continue even after 10 cycles in stationary state experiments for test samples. In addition, possibility of single beam overwrite(rewriting without prior erasing) is verified by using a 1.6 μm-diameter round laser beam spot on a 5-inch-diameter disk rotating at 2400rpm. The laser beam power is modulated at 1.77MHz and 0.88MHz between an amorphizing power level and a crystallizing power level. The amorphizing power level is 14mW and the crystallizing power level is 7mW. The experimental results show that the overwrite the same as magnetic disk is possible by using the In-Se based recording film.

Sn–Te–Se Films for Reversible Phase-Change Optical Recording

Characteristics of optical recording films that consist of Sn–Te–Se and have an amorphous crystalline phase change recording mechanism are analyzed. High crystallization temperatures and high crystallization activation energies, which certify the long life of the recorded dots, can be obtained for compositions whose ratio of Sn concentration to Se concentration is about 1 to 2. Among these compositions, high speed erasing, long life of the recorded dots, and high recording sensitivity are achieved in compositions whose Te concentration is 10 to 20 at%. When the Te concentration is 50 to 60 at% and the Se concentration is 17 to 25 at%, the crystallization temperature of the recorded dots is much lower than that of the as-deposited amorphous state.

Oxidation resistance of Pb‐Te‐Se optical recording film

The dependence of oxidation resistance of metal‐Te‐Se optical recording films on film composition is investigated, as well as the effects of oxidation on laser beam recorded hole shape. The films are deposited by vacuum evaporation on substrates with a glass/UV light curing resin/cellulose nitrate structure. The role of Se in the film is to inhibit the oxidation. With at least 14% Se addition, film oxidation is completely inhibited even at 60 °C, relative humidity 95%. Depth profiles of elements in the recording films are analyzed by Auger electron and x‐ray photoelectron spectroscopy to clarify the mechanisms of oxidation inhibition by Se addition. A selenium condensed layer is found at the inner part of an oxidized surface layer. The surface Te oxide layer and the Se‐rich layer should inhibit the film inside from oxidizing. The role of the metallic elements In, Pb, Sn, Bi, and Sb in the film is to inhibit cracking and to decrease noise in reproduced signals by decreasing the size of crystal grains. Lead...

Novel Stamper Process For Optical Disc

Two new types of stampers have been developed in order to improve the quality of optical discs and to simplify the process for manufacturing stampers. One is a plastic stamper which consists of a PMMA substrate and a photo-polymer resin layer having fine patterns such as pits and grooves on its surface. The other is a quartz stamper which has the pits and grooves with different depth formed on the surface of the quartz substrate by reactive ion etching process. Both these stampers can be made in a short processing time, and their quality is found to be higher than that of the conventional one. These stampers are transparent for ultraviolet light, so that they may also be used for making a replica disc with non-transparent substrate such as an Al substrate.

Sn-Te-Se Phase Change Recording Film For Optical Disks

Sn-Te-Se amorphous-crystalline phase change recording film is analyzed on write/erase cyclability, erasing speed, and activation energy of crystallization. The Sn-Te-Se thin film, sandwiched by two SiO2 thin film layers, is deposited on an organic-thick-film coated glass substrate. Then, another organic thick film is coated onto these layers. For these samples, the maximum erasure(crystallization) speed by laser beam irradiation and other write/erase characteristics are measured. Information can be written and erased more than 106 times. The crystallization activation energy is also measured and found to be about 2.3eV. The life of the amorphous state is estimated to be about 10 years at 40°C. These experimental results show that Sn-Te-Se thin film is promising as a reversible phase change recording film.