Noriyuki Kitaori

The application of a carbon protective layer to metal evaporated tape

Carbon protective layers for metal evaporated (ME) tapes were prepared using electron cyclotron resonance chemical vapor deposition (ECR-CVD). Raman spectroscopy was used to evaluate the carbon protective layers. It was found that the quantity of luminescent substances in the carbon film affected the overall durability of the protective layer. Raman spectroscopy was very useful in this analysis. Our results imply that not only hardness but also flexibility is required for the application of carbon films. The quantity of luminescent substances in the films was measured using a new parameter I b/I p, obtained from the Raman spectra. Protective layers with a particular range of I b/I p were found to be optimum durability. It is significant for the investigation of carbon protective layers that their durability can be easily determined by Raman spectroscopy.

Changes in Raman Spectra with Deposition Conditions and Plasma Treatment of Diamond Like Carbon Thin Films

A diamond like carbon (DLC) protective thin film was deposited on a Co evaporated magnetic recording tape by the electron cyclotron resonance chemical vapor deposition (ECR-CVD) method. The components of the DLC thin films were measured upon a changing the deposition conditions and plasma treatment conditions by means of Raman spectroscopy. It was found that the fluorescence level and graphite/diamond composition ratio in the DLC films influenced the film characteristics and could be controlled independently. The fluorescence level was estimated from the fluorescent background of Raman spectra and could be controlled by the reactive gas (100% C6H6) flow rate of the DLC film deposition time. In contrast, the graphite/diamond composition ratio could be controlled by means of the Ar plasma treatment after deposition. The composition ratio is the estimated parameter S1/S2 of the Raman spectrum area, where S1 is the low Raman band (nearly 1350 cm-1) area and S2 is the high Raman band (nearly 1530 cm-1) area. An increase in S1/S2 shows a high graphite ratio. The composition ratio was controlled from 0.43 to 2.04 using plasma treatment.

EFFECT OF SURFACE TREATMENTS ON ADSORPTION AND TRIBOLOGY OF THE DIAMOND-LIKE-CARBON LAYER FOR METAL-EVAPORATED TAPE

Metal-evaporated (ME) tape presents greater problems for smooth tracking and has poor durability than metal-particulate (MP) tape; a diamond-like-carbon (DLC) layer and a lubricant layer were used to cover the magnetic layer to overcome these problems. The surface state of the DLC protective layer must be controlled to enable the adsorption of fluorine of the lubricant. We investigated the surface state of the DLC protective layer using three types of surface treatments–aqua dipping, N2 plasma treatment, and a combination of the two–to study the change in lubricant adsorption. We found that N2 plasma treatment provided the most favorable surface for the realizaton of optimal ME tape properties.

Analysis of Columnar Microstructure in Fe–N Thin Films Prepared by an Ion-Assisted Vapor Deposition Method

Iron nitride thin film was produced through an ion-assisted evaporation process. After structural and elemental analyses using X-ray diffraction and energy dispersion X-ray spectroscopy it was judged that the film is e-Fe3N. It was found that this film consists of straight columns. Moreover, an X-ray line analysis across the columnar direction clarified that the sides of the columns are oxidized. In addition, the electron diffraction patterns obtained suggest that the c-axis of e-Fe3N (hexagonal) is in line with the direction of the columns.

Control of Surface Oxidation Layer Thickness in Metal Evaporated Tapes

The formation mechanisms of the surface oxidation layer and the oxidation inside metal evaporated tapes have been clarified. The Auger depth profiles of the samples deposited with various geometric arrangements of the oxygen gas flow nozzle were investigated. The surface oxidation layer is influenced by the oxygen partial pressure distribution around the can roll near the nozzle. The internal oxidation of the film is caused by the diluted oxygen gas after diffusion around the can roll. The results suggest that oxygen gas heating will cause a reduction in the thickness of the surface oxidation layer. The introduction of high-temperature metal vapor and radiant heat into the nozzle is effective in decreasing the thickness of the surface oxidation layer and significantly improves the playback output levels, particularly at short recording wavelengths.

Optimum Thickness of Magnetic Layer for Short-Wavelength Magnetic Recording.

Metal-evaporated (ME) tape contains no resin therefore, it has a high magnetic flux density that is superior to that of a conventional metal-powder (MP) tape. Thus, the ME tape has potential for use in high-density magnetic recording and in other new types of media. We prepared tapes whose magnetic layer thickness varied between 540 A and 3190 A. The tapes were produced continuously using Co oblique evaporation onto a base film. The fixed coercive force was maintained at about 1400 Oe. Using these tapes, we determined the optimum magnetic layer thickness needed to obtain a high video performance at short recording wavelengths. We also determined that the magnetic tape must have a certain minimum thickness for recording within a given system, and that the optimum thickness increases at a rate of 6% compared to the increase in the recording wavelengths. The difference from the theoretical ratio of 25% is thought to be due to the actual head gap length (0.22 µ m).