Investigation on the Graphitization Process of Amorphous Carbon for HAMR by Molecular Dynamics Simulation

QK Liu and LQ Li and HT Zhang and QT Huang and GY Zhang and ZX Hou, IEEE TRANSACTIONS ON MAGNETICS, 53, 3301007 (2017).

DOI: 10.1109/TMAG.2016.2626344

Molecular dynamics simulations are performed to investigate the laser- induced graphitization of amorphous carbon (a-C) films at different densities for heat-assisted magnetic recording. Physical insights into the graphitization caused by laser heating are provided by analyzing the virial pressure, bond angle distribution, radial distribution function, pair distribution function, and atomic strains during the laser heating and cooling process. The effects of density and laser irradiation times on the graphitization of a-C films are investigated. The laser-induced ultrafast nonthermal phase transformation occurs in the heating process. The sp(3)- sp(2) transformation is mainly contributed by the atoms in sp(3)- sp(3) bonds both in the heating and cooling process. Less energy is required for those atoms to overcome the energy barrier. The atomic shear strains and volume strains can accelerate the sp(3)- sp(2) transformation. For all a-C films at different densities, the rate of sp(2)- hybridized atoms increases rapidly in the first laser irradiation process.

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