Hiromu Chiba

Characterization of thick amorphous carbon films formed by pulse bias filtered cathodic vacuum arc

To form several-micrometer-thick diamond-like carbon (DLC) films, pulse bias filtered cathodic vacuum arc deposition was performed. In this study, nonhydrogenated DLC films were evaluated using visible and ultraviolet Raman spectroscopy, an electron energy loss spectroscopy (EELS) and a nano indenter. All observations indicated that the sp3 ratio of the DLC films decreases with increasing applied pulse bias. However, a moderately high sp3 ratio of 42.3% was obtained for 500-nm-thick DLC films with a compressive stress of 3.5 GPa formed at a pulse bias of 500 V, a pulse width of 25 µs, and a frequency of 1500 Hz.

Mechanical Characterization of Lapping Plate Materials in Diamond Charging Process

In the lapping of magnetic heads and other electronic components composed of multiple materials, differences in the processing characteristics of the composite materials result in “residual steps” forming on the surface at composite interfaces. Residual step heights have been reduced to as little as a few nanometers. We investigated using fine abrasives in fixed abrasive lapping for this purpose, which requires highly secure, high-density embedding of the abrasives on the lapping plate. To this end, we modeled the abrasive embedding process and investigated the relationship between the mechanical properties of the lapping plate and the retention of the abrasive, to determine the direction of further research and development. The results of this investigation revealed a correlation between the work hardening in the plate and the resulting abrasive density and cutting edge height. The investigation also showed that it is possible to suppress the reduction in lapping rate that occurs during use by increasing the work hardening coefficient of the plate.

Evaluation of GMR Head Durability against Nanoscale Scratches Using High-Field Transfer Curves

We investigated the durability of giant magnetoresistive (GMR) heads to nanoscale scratches created during the lapping process. Analysis using high-field transfer curves after deliberate scratching with an atomic force microscope (AFM) identified changes in the magnetization of the head and a reduction in pinning strength, which is a magnetic performance indicator. Additionally, finite element method (FEM) analysis suggested that the overall effects on the GMR head following nanoscale scratching increased with scratch depth.