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The Effect of Media Substrate Topography On The Carbon Coating Coverage; A Molecular Dynamics Study at Fuji Electric

Ammerlaan, B.P. (2015) The Effect of Media Substrate Topography On The Carbon Coating Coverage; A Molecular Dynamics Study at Fuji Electric. Master's Thesis / Essay, Industrial Engineering and Management.

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This thesis has had two goals, the first goal was to create and start the development of a simulation model for Fuji Electric that was able to model the deposition process of the carbon coating on top of the media substrate. The second goal of this study was to gain more knowledge on how the coverage of the carbon coating is affected by the deposition process and the media substrate topography. The R&D department of Fuji Electric needs to create thinner carbon coatings in order to facilitate further improvements in the recording density. The protective carbon layer has been reduced over the years and this has lead to a smaller distance between the read/write head and the magnetic layer. An average increase in recording density of 44% per year till 2006 was the consequence of this reduction in magnetic spacing. Since 2006 this slowed down dramatically to 8-12% per year and one of the reasons is that the carbon film thickness has become so thin that sufficient coverage has become problematic, resulting in corrosion problems. The Molecular Dynamics simulation model created with LAMMPS in this study has an incidence energy of 6eV, 0⁰ incidence angle and the substrate is composed out of cobalt atoms with a substrate size of 176Å x 176Å x 76Å. The potentials used for C-C interaction is the Tersoff potential, for Co-Co the potential developed by Purja Pun et al. is used, and for the C-Co interaction a Lennard-Jones potential with the parameters epsilon=0.2eV and sigma=1.51Å is applied. The results from the simulation model predict that the current substrate topography of the media disk substrate, characterized with the Rq (RMS) and correlation length T, needs a carbon coating thickness of 0.85-0.96nm, based on a carbon atom size range of 2.19-3.40Å. (Coverage is assumed when the probability that the thickness is 1 carbon atom thick is equal or smaller than 1%). The growth preference of the carbon atom is studied and the results show, like other works, that the preference of carbon atoms is to grow in the valleys and less on the hills of the media substrate. The results from this thesis show that substrate topography is an important factor regarding further improvements of the carbon coating and recording density.

Item Type: Thesis (Master's Thesis / Essay)
Degree programme: Industrial Engineering and Management
Thesis type: Master's Thesis / Essay
Language: English
Date Deposited: 15 Feb 2018 08:03
Last Modified: 15 Feb 2018 08:03

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