Yuichi Kokaku

Influence of exposure to an atmosphere of high relative humidity on tribological properties of diamondlike carbon films

‘‘Diamondlike’’ carbon films have potential applications because of their high wear resistances. We have investigated the influence of exposure to an atmosphere of high relative humidity (RH) on tribological properties of carbon films prepared with a radio‐frequency plasma enhanced chemical vapor deposition. Wear characteristics were measured using a pin‐on‐disk wear tester. A friction coefficient of a carbon film as deposited was as low as 0.2. However, the value increased up to 0.3–0.4 after exposure to an atmosphere of 60 °C 90% RH for seven days. Electron spectroscopy for chemical analysis and electron energy‐loss spectroscopy analysis suggested that a very thin (<1 nm) unstable surface layer of the film had suffered a chemical change during the exposure process. We have found that the change can be suppressed by increasing a degree of fragmentation of the hydrocarbon source in the plasma, or by removing the unstable layer with an Ar plasma etching.

Performance of hard DLC protective film prepared by PECVD method for thin film magnetic disk

Performance of a diamondlike carbon (DLC) film prepared by the PECVD method has been investigated as the protective film of a rigid thin film disk. An in-line sputtering PECVD multilayer deposition system was used for preparation of disk samples. The disks were found to be superior to those disks with conventionally sputtered carbon films in many aspects such as high durability against CSS tests, smooth coverage over the irregular points of the magnetic layer, and as a result, good corrosion resistance even at a thickness of 15 nm or less. >

Properties Of Diamond-like Carbon Films And Its Application For Protective Layers Of Thin Film Magnetic Recording Disks

Wear rate of diamond-like carbon (DLC) protective layer deposited by a radio frequency plasma enhanced chemical vapor deposition method has been evaluated by continuous sliding tests using spherical sapphire pins. The influence of each property such as microstructure and microhardness on wear durability of the film is discussed. It has been found that the wear durability of the DLC film is several times superior to that of conventional sputtered carbon film. >

STRUCTURAL ANALYSIS OF HYDROGENATED CARBON FILMS OBTAINED BY REACTIVE DIRECT CURRENT MAGNETRON SPUTTERING

Amorphous hydrogenated carbon films were prepared by reactive direct current magnetron sputtering in argon plasma containing methane as the reactant gas. The films were characterized using various spectroscopic measurements such as Raman scattering, optical absorption spectroscopy in the ultraviolet–visible region, and infrared (IR) absorption spectroscopy. The spectral analyses indicated that changes in Raman spectroscopy intensity occurring with increasing methane gas content were determined to be caused by changes in optically resonant components in the films. Furthermore, a significant correlation was seen between the relative intensity of IR peaks and wear durability.

Effect of microstructure and hydrogen content on the characteristics of amorphous hydrogenated carbon protective coatings

Amorphous hydrogenated carbon films have splendid wear characteristics as protective coatings. In the present work we have studied the relation between wear durability and microstructure of the amorphous hydrogenated carbon films prepared with radio‐frequency plasma‐enhanced chemical vapor deposition. Wear rates of pin‐on‐disk sliding tests for the films deposited at various conditions have been compared with the results of spectroscopic analysis. Wear durability of the films has been found to be described with a combination of two factors, one is the shoulder‐to‐main peak ratio of Raman spectra and the other is content of chemically bonded hydrogen atom. The former factor stands for the amount of ‘‘graphitelike’’ regions and the latter stands for the amount of ‘‘organic’’ regions in the carbon films.

A new x-ray metrology for profiling nanostructures of patterned media

We have developed a new x-ay metrology for profiling surface periodic structure of discrete track patterned media. X-rays irradiate surface of the discrete track media with a shallow glancing angle, which is close to the critical angle of total external reflection of the surface material. The measured x-ray scattering pattern is reflected to the average cross-sectional profile of the grating. Resist pattern of circular discrete track with120 nm-pitch on 65 mmφ magnetic disc is analyzed by the present x-ray metrology. The obtained profile, for example, line width, height of the track and so on are well agreed with that observed by cross-sectional scanning electron microscopy. The wavelength of x-ray that we use is 0.154093 nm and it is enough shorter than the critical length of the grating structure, even when the track width becomes 10 nm or less. Therefore, the resolution of the x-ray metrology will be maintained well that of required in future. In addition, x-ray metrology is able to profiling the cross-sectional structure with nondestructively due to hightransmissivity of x-rays for the materials. Furthermore, the optical parameter of the materials is well established in x-ray region, therefore, it is applicable not only resist patterns, but also real device patterns only with certain physical/optical parameters.