Microstructure and Tribological Properties OF Co-Cr thin Films Deposited by Facing Targets Sputtering and Magnetron Sput
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MICROSTRUCTURE AND TRIBOLOGICAL PROPERTIES OF Co-Cr THIN FILMS DEPOSITED BY FACING TARGETS SPUTTERING AND MAGNETRON SPUTTERING METHODS SADAO KADOKURA * and MASAHIKO NAOE* *Teijin Ltd., Advanced Thin Film Research Labs.,Tokyo Japan "*Tokyo Institute of Technology, Department of Physical Electronics, Tokyo, Japan ABSTRACT The tribological properties and the slid surface profiles of Co-Cr thin films deposited by Facing Targets sputtering and Magnetron sputtering methods were investigated in regard to the durability of flexible disks. Co-Cr thin films with columnless microstructure and homogeneously packed particles were much tougher than ones with columnar microstructure for tribological test. The Co-Cr films deposited by conventional Magnetron sputtering method revealed typically columnar structure, while ones deposited by Facing Target sputtering method did columnless microstructure. This indicates probably homogeneous distribution of strong bonding forces between grain boundaries throughout the films, because no brittle fracture was observed even after the delamination between a plastic substrate and the CoOx/ Co-Cr / Ni-Fe triple layers took place by application of excess stresses. Itwas found that difference in morphology of Co-Cr thin film between Facing Target sputtering and conventional Magnetron sputtering methods was much significant. INTRODUCTION Co-Cr thin films are suitable for perpendicular magnetic recording media with ultra-high density. The films deposited by conventional sputtering and evaporation methods consist of columnar grains with good c-axis orientation of hcp crystallites. The origin of the perpendicular magnetic anisotropy has been reported to be correlated with columnar structure of Co-Cr films [1,2]. However, Co-Cr thin films deposited by Facing Target sputtering (FTS) method reveal columnless microstructure with their superior c-axis orientation even at thickness as small as 10 nm [3]. The tribological properties of flexible media for high density magnetic recording are considered to be strongly related with microstructures of Co-Cr thin films [4]. One of the authors reported that the flexible disks with Co-Cr thin films deposited by FTS web coater have much impoved signal durability in comparison with ones by DC magnetron sputtering (DCM) web coater [5]. In this study, tribological properties and microstructures of Co-Cr thin films media were investigated for the triple layer flexible media with CoOx protective layer composed of Ni-Fe and Co-Cr thin layers in order deposited on both sides of polyethylene telephthalate (PET) film substrate by using DCM and FTS web coaters. The CoOx layers were deposited by RF sputtering method. In this paper, the morphological differences in deposited thin layers between DCM and FTS methods were discussed and clarified. EXPERIMENTAL
RESULTS
The layer thicknesses and magnetic properties of the triple layer flexible disks are listed in Table 1 [ 5]. The Co-Cr / Ni-Fe double-layers of A and B disks were deposited by using the FTS web coater, while ones of
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