To achieve high-performance of switching-field sensitivity in a magneto-optical disk system using magnetic field modulation, we focused on the study of the characteristics of the first dielectric layer becouse it's performance has the strongest influence on the magnetization characteristics and the reliability of the recording layer. We therefore worked on optimizing the parameters for sputtering control in order to obtain a superior recording performance. At the same time, we were able to confirm that the best results could be obtained by setting the ratio of neodymium at 1.0at% in the composition of the neodymium-dysprosium-iron-cobalt (NdDyFeCo) magnetic layer. By having determined the optimum solutions to fabricating higher performance media, we were able to develop the lower cost, superior-sensitivity magneto-optical disks to be reported here.
Copper and copper oxide thin films were prepared by reactive rf sputtering on glass substrates, and their electrical and optical properties were investigated. Pure copper disks were employed as the targets and mixtures of argon and oxygen as the sputtering gases. Copper oxide thin films with various oxygen contents were obtained by changing the oxygen concentration of the sputtering gas and the rf power density, and X-ray diffraction confirmed that the oxygen content of the films increased from Cu to CuO (i, e., in the order of Cu, Cu+Cu2O, Cu2O, Cu2O+CuO and CuO) with increases in the oxygen concentration of the sputtering gas. The sputtering condition for the formation of Cu2O was found to be very limited. Film resistivity, on the whole, increased with increases in the oxygen content of the specimens. The resistivity of Cu films decreased as their crystallinity increased. This phenomena may be attributed to electron scattering by structural defects. In CuO, on the other hand, film resistivity increased with increases in film crystallinity, indicating that carrier generation due to structural imperfections plays an important role in electrical conduction. Films consisting of Cu and Cu+Cu2O showed metallic conductivity, while those consisting of Cu2O, Cu2O+CuO and CuO showed semiconductive behavior. The latter group also showed photoconductivity.
Thin films of (Ti-Zr) nitride and (Ti-Zr) carbide were prepared on WC-Co substrates by the arc ion plating (AIP) process. The Ti-Zr composition of the film was similar to that of the targets used. Deviations in Ti-Zr composition in the AIP process were found to be very small, even in nitriding and carbiding reactions. Thus This process is suitable for the formation of thin films of alloys or ceramics composed of metals with greatly differing vapour pressures. The maximum hardnesses were Hv: 3300 for (Ti-50at%Zr)N and Hv: 4000 for (Ti-50at%Zr) C. The crystal structures and orientations of the thin films having maximum microhardnesses were characterized by X-ray diffraction (CuKα, 35kV-30mA). (Ti-Zr) nitride was found to have a (111) preferred orientation, while (Ti-Zr) carbide had (111) and (200) preferred orientations.
Silicon oxide films were prepared on polyethylene terephthalate film by radio-frequency plasma chemical vapor deposition using hexamethyl disiloxane (HMDSO) and oxygen gas and intentionally not heating the substrate. We studied the influence of the surface conditions of the substrate on gas permeability of films. We also studied the compositional and structual properties of films through infrared absorption, refractive indexing, and X-ray photo-electron spectroscopy (XPS). Silicon oxide films prepared by using HMDSO and oxygen gas plasma featured high gas-barrier properties, which were affected by the surface conditions of the substrate. We confirmed that it was necessary to bombard the substrate using HMDSO plasma as a pretreatment in order to obtain a silicon oxide film with higher gasbarrier properties.
Diamond films were grown at low temperatures (630-813K) on Si, Al (1100P), and Al-Si (8A, 8B, 8C) alloy substrates using microwave plasma chemical vapor deposition (CVD) in a mixed methane and hydrogen gas reaction system. When the methane concentration was high and growth was conducted at lower pressures the diamond films were synthesized and the deposits on the scratched substrates formed flat surfaces consisting of fine grains. XRD results, confirmed that the deposits were cubic diamond. An analysis using Raman spectroscopy, further confirmed that diamond films deposited on the Si substrates were of high quality. The deposits on the Al substrates, in contrast, contained amorphous carbon. While the quality of the deposits on the Al-Si alloy substrates were differed with the substrate alloy. We assume that this phenomenon was caused by the chemical components of the individual substrates. Viewed from a comparison of the individual substrate growth conditions, the mechanism underlying low-temperature-growth diamond synthesis thus appears to consist of an overlapping of factors such as Te, Tg, Ne, and the carbon source concentration complex from comparison of their growth conditions.
Plasma polymerized films of carbocyclic compounds such as C6H12, C6H6, C6H5CH3, C6H5NH2, C3H5Cl, and C6H5OH were deposited on expanded graphite sheets and film durability was investigated by measuring cathodic polarization curves in aerated NaCl solution. The polymer film-coated sheets were employed as the working electrode. The films of hydrocarbons having a highly crosslinked structure (C6H12, C6H6, and C6H5CH3) inhibited cathodic reactions, and in these cases the main reaction is thought be oxygen reduction: H2O+1/2O2+2e-=2OH-. But in the other compounds studied, little inhibition occurred. In the hydrocarbons, cathodic activity was related to the O1s/C1s ratio obtained by X-ray photoelectron spectroscopy (XPS) and to the surface potential (SP) measured by a conventional vibrating electrode method. The cathodic reaction activity of the films decreased as the oxygen content decreased and as the surface potential decreased. It is suggested that the chemical and electrical nature of the hydrocarbon films plays an important role in cathodic reaction activity. Anodic polarization was also carried out for the C6H12 and C5H5OH films. The trend in the inhibiting effect was similar to that for cathodic polarization.
Electroless nickel-iron-boron alloy deposits containing dimethylamine boron as a reducing agent were investigated for corrosion resistance in 5wt%NaCl (pH7, 303K) by immersion tests and measurements of external polarization curves and corrosion potential. The following results were obtained: (1) At a bath pH of 7 to 11, the corrosion resistance of the deposits improved the higher the pH. (2) When the iron ion concentration in the bath was changed, while the total concentration of nickel ion plus iron ion was kept at 0.1mol/L, the corrosion resistance of deposits containing iron was better than that of nickel-boron deposite but at greater iron contents, corrosion resistance tended to decreased.
The effect of the insertion of a Ti glue layers to enhance adhesion between Pt films and Ti oxide films has been investigated. Ti is known to be effective in adhesion enhancement, but the diffusion of Ti atoms into Pt films caused by heat treatment adversely affected bonding between the Pt films and Au wire. HRSEM and AES were used to analyze the behavior of the Ti atoms and it was found that excessive Ti atoms in the glue layer diffused onto the Pt surface. It was found that 5nm was the optimum thickness of the Ti glue layer in terms of both enhancing adhesion and suppressing deterioration of Au wire bonding.
Fe was electrodeposited on (100), (110) and (111) Au single crystalline thin films, and the double-layered Fe/Au films were examined by electron microscope. In the initial stage of electrodeposition, disk crystalline nuclei of Fe formed on the Au substrates and as the electrodeposition proceeded, they grew epitaxially to form a continuous layer of 15∼20nm in mean thickness. Epitaxial relationships were as follows; (100)Au||(100)Fe Au||Fe, (110)Au||(110)FeAu/Fe and (111)Au||(110)Fe‹110›Au||Fe. When the thickness of the Fe layer exceeded a critical value, interfacial dislocations, also known as misfit dislocations, were introduced into the interface between the Fe and Au layers. Edge type dislocations of Burgers vectors of a/2 ‹011› were formed in Fe/(100)Au, and mixed type dislocations of Burgers vectors of a/2 ‹110› were formed both in Fe/(110)Au and Fe/(111)Au. The critical thickness for introducing dislocations was estimated at 15∼20nm. Formation of the interfacial dislocations resulted in the relaxation of internal stress originating in the misfits between the Fe and Au lattices.
Iron-carbon alloy films with 0.43 to 1.18mass%C were electrodeposited from an iron (II) sulfate solution containing small amounts of citric acid and L-ascorbic acid. Phase transformations and hardness changes in the alloy films resulting from annealing at 473K to 1173K for 3.6ks were studied by X-ray diffraction and hardness measurement. The alloy films had a single martensitic phase with a body-centered tetragonal structure, and the axial ratio of the phase increased with the increase in the C content in the films. A new intermediate carbide phase and Fe3C phase were formed on annealing at 623K and 1173K. The intermediate carbide phase had an orthorhombic structure with a=0.4787nm, b=0.4360nm and c=0.2902nm. The increase in the hardness of the Fe-C alloy films at carbon contents of above 1mass% started at around 473K, and softening began at about 753K. The alloy films annealed at temperatures between 473K and 753K showed the hardness of Hv 1000 to Hv 1100 at room temperature.