Molecular dynamics approach for the calculation of surface loss probabilities during the growth of C:H films from an argon-methane plasma
Résumé
Low-temperature hydrocarbon plasmas are media where a large variety of different species coexist, encouraging their use in many different applications requiring the deposition of thin films or the synthesis of nanoparticles and nanocomposites [1]. The complex chemistry occurring in these plasmas makes their understanding and controlling rather difficult, as it involves reactions in both the plasma volume and on the surrounding surfaces. The present work deals with molecular dynamics simulations of the interaction of the main neutral species previously obtained using a 1D fluid model [2] (H2, CH4, C2H4, C2H2, CH3, and C2H) of an argon-methane plasma with the grounded electrode of a capacitively-coupled rf discharge. Simulations were performed by sending all the species (49200 molecules) towards the surface, at a rate of one molecule every 2000 time steps (i.e. every 500 fs), taking into account the molar fraction of each species. The study was carried out at temperatures from 300 K to 1000 K over a total simulation time of 26 ns. The results showed that the C2H radical is the main precursor of the film growth even if its bonding coefficient progressively decreases as the film grows due to an increased probability of formation of volatile species after its interaction with the surface. The CH3 radical very little contributes to the film growth as most of these molecules interact with the surface to give new volatile species. The stable molecules such as CH4 and C2H4 are mainly reflected from the surface as they are, except at 1000 K where they can be fragmented after their interaction with the surface.
Acknowledgements
This work was partly supported by the French National Research Agency (ANR) through the MONA project (ANR-18-CE30-0016)
References
[1]G. O. Kandjani et al, Plasma Process. Polym., e2200192 (2022)
[2]G. Tetard et al, Plasma Sources Sci. Technol. 30, 10, (2021)
[3]C. Hopf et al, Appl. Phys. Lett. 74, 25, (1999)