Effects of substrate bias voltage on structure and internal stress of amorphous carbon films on gamma-Fe substrate: Molecular dynamics simulation

SL Zhang and YF Zhou and W Shao and TS Hu and LX Rao and ZJ Shi and XL Xing and QX Yang, COMPUTATIONAL MATERIALS SCIENCE, 188, 110206 (2021).

DOI: 10.1016/j.commatsci.2020.110206

In this paper, the deposition process of amorphous carbon (a-C) films on gamma-Fe substrate was simulated by molecular dynamics (MD). The effects of substrate bias voltage (abbreviated as bias) on structure and internal stress of a-C films was investigated. The results showed that the growth process of a-C films on gamma-Fe substrate can be divided into five stages, namely, the diffusion stage of C atoms, island-like nucleation stage of a-C films, formation stage of the pseudo diffusion zone, diffusion stage of Fe atoms and stable growth stage of a-C films. The structure of a-C films after deposition can be divided into four zones, namely, the substrate zone, pseudo diffusion zone, intrinsic zone and surface zone. The intrinsic zone is the main part of a-C films, and its structure is mainly composed of sp(3)-C and sp(2)-C atoms. The percentage of sp(3)-C atoms is fluctuated with the increase of bias. When bias is 25 V, the percentage of sp(3)-C atoms is the largest, which is 26.19%. When bias is 75 V, the percentage of sp(3)-C atoms is the smallest, which is 23.92%. The percentage of sp(2)-C atoms is increased with the increase of bias. When bias is 75 V, the percentage of sp(2)-C atoms is the largest, which is 73.69%. With the increase of bias, the internal stress of the intrinsic zone is firstly increased. When bias is 25 V, the internal stress is the highest, which is 6.94 GPa and then is decreased gradually. The pseudo diffusion zone is a transition zone between a-C films and gamma-Fe substrate, and is a mixed zone composed of C and Fe atoms. With the increase of bias, the internal stress in the pseudo diffusion zone is decreased gradually. When bias is 75 V, the internal stress is the lowest, which is 0.40 GPa.

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