Properties Oftetrahedralamorphous Carbon Films Deposited By the Filtered Cathodicarc Method
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PROPERTIES OF TETRAHEDRAL AMORPHOUS CARBON FILMS DEPOSITED BY THE FILTERED CATHODIC ARC METHOD Naruhisa Nagata, Kazuhiro Kusakawa, Akiyasu Kumagai, and Hideaki Matsuyama1 Fuji Electric Corporate Research and Development, Ltd., Device Technology Laboratory, Matsumoto, Nagano, JAPAN 1 Fuji Electric Corporate Research and Development, Ltd., Material Science and Technology Laboratory, Yokosuka, Kanagawa, JAPAN ABSTRACT First, we studied the relation between the sp3 bond ratio and the hardness of 100-nm-thick tetrahedral amorphous carbon (ta-C) films deposited by a Filtered Cathodic Arc (FCA) system at different substrate bias voltages. For comparison, sputtered amorphous carbon (a-C) films and Highly Oriented Pyrolytic Graphite (HOPG) were also analyzed. According to the results, ta-C film deposited at a -70 volt substrate bias voltage had high hardness and high sp3 bond ratio of up to 88 GPa and 85%, respectively, whereas those of sputtered a-C were 29 GPa and 28%. Furthermore, we found that the hardness of carbon films, including sputtered a-C and HOPG, increased with increasing sp3 bond ratio. Based on this relation, the chemical bond structures of carbon films are considered to be closely related to their mechanical properties. Secondly, we investigated the relation between sp3 bond ratio and ta-C film thickness, over the range from 1 to 10 nm. The measurements showed that a 2-nm-thick initial layer grown on the surface of CoCrPt magnetic film had low sp3 bond ratios. It is suggested that this reduction in sp3 bond ratio in the initially grown layer seriously sp3 Diamond degrades the film’s performance as a hard disk media overcoat. Further efforts to improve ta-C film ta-C processing will be required to improve its mechanical properties. a-C:H INTRODUCTION
a-C Polymer
Recently, the areal recording density of hard disk drives has been increasing rapidly, and reduction of the magnetic spacing between the head and hard disk media is being required. To achieve this reduction, it is necessary to reduce the thickness
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Figure 1. Diagram of carbon films [1,2]
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of the hard disk media overcoat, as well as the head flying height and lubricant thickness. Ta-C film holds promise as a next generation overcoat material for hard disk media due to its high hardness. Ta-C is a hydrogen-free and highly sp3 bonded amorphous carbon (Figure 1 [1,2]). It can be grown by the FCA method [3,4,5,6,7], which is a vacuum arc deposition method. In this study, we paid close attention to the ratio of sp3 to sp2 bonds in ta-C film, an important parameter representing the chemical bond structure of carbon. EXPERIMENTAL DETAILS
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We used the FCA method for growing ta-C films, and the FCA system that was employed is shown in Figure 2. UWDUVTCVG #TE UQWTEG The cathode target is graphite having 99.999% purity and is columnar, with dimensions of 30 mm in diameter and 30 mm in length. The anode is a coiled copper tube, /CIPGVKE having 9 turns per 60 mm long and a coil HKNVGT ECVJQFG CPQFG diameter
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