Energy-dependent trapping of backscattered helium during magnetron sputtering growth: A molecular dynamics study
Abstract
Helium incorporation during magnetron sputtering can strongly affect thin film growth and lead to the formation of gas/solid nanocomposites and nanoporous structures. Here, molecular dynamics (MD) simulations are used to investigate the trapping mechanism of helium atoms (He) and the subsequent formation of He bubbles during the sputter deposition of aluminum (Al) and titanium (Ti) thin films. The simulations account for the kinetic energy distributions of sputtered metal atoms and backscattered gas species. Results indicate that He is efficiently incorporated into the growing films, leading to the formation of high-pressure, dense He bubbles, with a much higher He-to-metal atomic ratio in Ti (∼ 60%) than in Al (∼ 12%). More importantly, the simulations reveal a clear energy dependence of He trapping in Ti: background He atoms at thermal energies are essentially not incorporated, whereas efficient trapping starts at an incident energy of approximately 20 eV and increases up to a saturation regime near 100 eV. Simulated thermal desorption spectroscopy (TDS) further reveals distinct release mechanisms in the two investigated metals: He desorption from Al occurs at higher temperatures and is preceded by the removal of surface Al atoms, whereas He and Ti atom desorption starts continuously around 950 K, leading to a porous structure. Comparative simulations with argon (Ar) demonstrate negligible trapping even at comparable kinetic energy or momentum, showing that neither parameter alone accounts for the strong He incorporation observed in Ti. The above results are in very good agreement with what is reported in literature for low-kinetic energy He ion implantation in metal surfaces, suggesting similar insertion mechanisms. They clarify the atomistic conditions governing noble gas trapping during film growth and provide a basis for controlling He incorporation and porosity in films synthesized by magnetron sputtering.
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BibTeX
@misc{brault2026energydependent,
title = {{Energy-dependent trapping of backscattered helium during magnetron sputtering growth: A molecular dynamics study}},
author = {Pascal Brault and Anne-Lise Thomann and Alejandro Borroto},
howpublished = {HAL},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.13509},
eprint = {2610.13509},
archivePrefix = {arXiv},
url = {https://hal.science/hal-05788383v2},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Energy-dependent trapping of backscattered helium during magnetron sputtering growth: A molecular dynamics study
AU - Pascal Brault
AU - Anne-Lise Thomann
AU - Alejandro Borroto
PY - 2026
DA - 2026/10/08
PB - HAL
DO - 10.48550/arxiv.2610.13509
UR - https://hal.science/hal-05788383v2
AB - Helium incorporation during magnetron sputtering can strongly affect thin film growth and lead to the formation of gas/solid nanocomposites and nanoporous structures. Here, molecular dynamics (MD) simulations are used to investigate the trapping mechanism of helium atoms (He) and the subsequent formation of He bubbles during the sputter deposition of aluminum (Al) and titanium (Ti) thin films. The simulations account for the kinetic energy distributions of sputtered metal atoms and backscattered gas species. Results indicate that He is efficiently incorporated into the growing films, leading to the formation of high-pressure, dense He bubbles, with a much higher He-to-metal atomic ratio in Ti (∼ 60%) than in Al (∼ 12%). More importantly, the simulations reveal a clear energy dependence of He trapping in Ti: background He atoms at thermal energies are essentially not incorporated, whereas efficient trapping starts at an incident energy of approximately 20 eV and increases up to a saturation regime near 100 eV. Simulated thermal desorption spectroscopy (TDS) further reveals distinct release mechanisms in the two investigated metals: He desorption from Al occurs at higher temperatures and is preceded by the removal of surface Al atoms, whereas He and Ti atom desorption starts continuously around 950 K, leading to a porous structure. Comparative simulations with argon (Ar) demonstrate negligible trapping even at comparable kinetic energy or momentum, showing that neither parameter alone accounts for the strong He incorporation observed in Ti. The above results are in very good agreement with what is reported in literature for low-kinetic energy He ion implantation in metal surfaces, suggesting similar insertion mechanisms. They clarify the atomistic conditions governing noble gas trapping during film growth and provide a basis for controlling He incorporation and porosity in films synthesized by magnetron sputtering.
ER -