Study of mechanical properties of silicon-doped diamond-like carbon films based on molecular dynamics simulation

Abstract

Mechanical properties of diamond-like carbon (DLC) films, doped with different concentrations of silicon (Si), were studied using molecular dynamics (MD) simulation. Si with different concentrations of Si = 0, 5, 10 and 15 at.% C (atomic percentage relative to 6435 carbon atoms) were added to a region simulation block occupied by 6435 carbon (C) atoms, using the silicon-carbon (SiC) Tersoff potential in Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS). Amorphous DLC films, with the different amount of Si, are prepared by simulation of the melt-quenching procedure. Subsequently the prepared simulated Si-DLC films undergoes a deformation control tensile test. This study examines the effects of Si doping concentrations with mechanical properties such as Young’s modulus, toughness and ultimate tensile strength of the DLC film using the stress-strain curves. The radial distribution function (RDF) of crystalline structures found in diamond are also compared with that of amorphous carbon (a-C). The localization and necking due to atomic strain of the DLC films during the tensile test are also examined. Lastly the fraction of sp3 hybridised bonds in the Si-DLC film is analysed. Results from the simulation demonstrates that the increase of concentrations of Si contributes to the decreased sp3 bonding fraction between the C atoms despite an increase in sp3 bonding found in Si atoms which results in the Si-DLC films having more graphitic properties. Small and large concentrations Si also caused differences in mechanical properties of the Si-DLC films.