Formation of molecular hydrogen in diamond-like carbon films during deposition: Molecular dynamics simulations

• Published in: Diamond and related materials 2024-11, Vol.149, p.111580, Article 111580
• Main Authors: Li, Xiaoling, Peng, Jihua, Peng, Da
• Format: Article
• Language: English
• Subjects: Deposition mechanism; Hydrogenated carbon film; LAMMPS; Unbonded hydrogen
• ISSN: 0925-9635
• DOI: 10.1016/j.diamond.2024.111580

The existence states of the H atoms in hydrogenated diamond-like carbon (a-C:H) films were simulated using a modified REBO II potential function-based large-scale atomic/molecular parallel simulator (LAMMPS) and neutral C and H atom beam impingement. The fraction of the H atoms in the incident source (H-flux fraction) in the source must be considered when investigating the effects of the incident energy combination on the H content and mass density of the films. In simulations a-C:H film deposition using a 15 % H-flux fraction, films with densities of 2.6–2.8 g/cm3 could be obtained, and their H content varied with the incident energy. However, the H contents of films simulated using a 70 % H-flux fraction could be kept in the range of 40–50 at.%. The H atoms in the films preferentially reacted with the C atoms to form CH bonds. Regardless of the incident energy combination used, the total sp3C fraction in the film increased with the H-flux fraction of the source. An incident energy of >36 eV for the H atoms was necessary to form H2 during the film deposition. Instead of being formed in the surface growth zone, H2 molecules were synthesized in the stabilized zone, where a high density of sp3C—Hn was favorable. [Display omitted] •Simulation of H atom states in hydrogenated carbon films using LAMMPS•The incident energy and H-flux fraction of H atoms were the keys to controlling the H content and density of the films.•An incident energy of 36 eV was necessary for the formation of H2 in the films.•H2 existed in the stabilized zone owing to the reaction between the implanted H and sp3C-Hn.