Intermediate Carbon Layer Research Articles

Effects of thin carbon intermediate layer on magnetic and structural properties of perpendicular recording media

CoCrPt/CoCr/carbon films were sputter-deposited on CoTaZr soft-magnetic underlayers and the effects of a carbon intermediate layer on magnetic and recording properties were investigated by changing a heating sequence in sample preparations. A heating process before a CoCr deposition was needed to obtain a high perpendicular coercivity. The carbon diffusion into a CoCr layer during its deposition led to small crystal grains in the CoCr layer and thereby the CoCrPt layer. Consequently, a high perpendicular coercivity was obtained, which was considered due to the change in magnetization process from a wall motion to a coherent rotation. The use of a thin (1–5 nm) carbon intermediate layer was found to be effective to obtain both low noise and high resolution.

アモルファスＳｉ中間層を用いた垂直面内複合型媒体の作製

Sputter-deposited Si was applied as an intermediate layer of a perpendicular/longitudinal composite medium. In the case of the composite media with a carbon intermediate layer, a paramagnetic Co-Cr film with a 20 nm thickness was necessary for inhibiting diffusion of the C atoms into the magnetic layer. AES analysis revealed that Si atoms diffuse very little into the longitudinal and perpendicular magnetic layers, which means that the extra intermediate layer is unnecessary. Accordingly, intermediate layer thickness was reduced to 5 nm by applying Si.In a read/write experiment, the composite medium exhibited a higher reproduced voltage than the perpendicular single-layered medium up to 400 kFRPI, which is attributed to the thin intermediate layer. Moreover, it was found that the composite medium has better thermal stability than the single-layered medium at a recording density of 2 kFRPI.

Oxidation Behavior of Si‐C‐O Fibers (Nicalon) under Oxygen Partial Pressures from 102 to 105 Pa at 1773 k

Polycarbosilane‐derived SiC fibers (Nicalon) were oxidized at 1773 K under oxygen partial pressures from 102 to 105 Pa. The effect of oxygen partial pressure on the oxidation behavior of the Nicalon fibers was investigated by examining mass change, surface composition, crystal phase, morphology, and tensile strength. The Nicalon fibers were passively oxidized under oxygen partial pressures of >2.5 ×102 Pa and actively oxidized under an oxygen partial pressure of 102 Pa. Under oxygen partial pressures from 2.5 × 102 to 103 Pa, active oxidation occurred at the earliest stage of oxidation, resulting in the formation of both a silica film and a carbon intermediate layer. Although the unoxidized core retained considerable levels of strength under the passive‐oxidation condition, fiber strength was lost under the active‐oxidation condition.

Preparation of Diamond Mold Using Electron Beam Lithography for Application to Nanoimprint Lithography

Diamond molds were fabricated by two types of fabrication processes, both of which use a conductive intermediate layer between the diamond surface and polymethylmethacrylate (PMMA) resist to prevent surface charge-up. Using a PtPd intermediate layer, electron beam lithography and ion beam etching, a denting line pattern of 600 nm width and 70 nm depth was fabricated. Using a carbon intermediate layer, electron beam lithography, PtPd lift-off and oxygen ion beam etching, a convex line pattern of 600 nm width and 110 nm height was fabricated. These diamond molds were pressed into PMMA on a silicon substrate that was heated to a temperature of 150°C and kept at a pressure of 23.5 MPa until the temperature dropped below 90°C, and then the diamond mold was released from the PMMA. The convex line pattern of 600 nm width and 150 nm height was imprinted using a denting diamond mold. The denting pattern of 1100 nm width and 180 nm height was imprinted using a convex diamond mold. PMMA patterns were transferred well over the imprinted area by the diamond molds.

In situ growth rate measurement and nucleation enhancement for microwave plasma CVD of diamond

Laser reflection interferometry (LRI) has been shown to be a useful in situ technique for measuring growth rate of diamond during microwave plasma chemical vapor deposition (MPCVD). Current alternatives to LRI usually involve ex situ analysis such as cross-sectional SEM or profilometry. The ability to measure the growth rate in ‘real-time’ has allowed the variation of processing parameters during a single deposition and thus the extraction of much more information in a fraction of the time. In situ monitoring of growth processes also makes it possible to perform closed loop process control with better reproducibility and quality control. Unfortunately, LRI requires a relatively smooth surface to avoid surface scattering and the commensurate drop in reflected intensity. This problem was remedied by greatly enhancing the diamond particle nucleation via the deposition of an intermediate carbon layer using substrate biasing. When an unscratched silicon wafer is pretreated by biasing negatively relative to ground while in a methane-hydrogen plasma, nucleation densities much higher than those achieved on scratched silicon wafers are obtained. The enhanced nucleation allows a complete film composed of small grains to form in a relatively short time, resulting in a much smoother surface than is obtained from a film grown at lower nucleation densities.