Role of chemical interactions on retention and sputtering behavior in boron films under deuterium ion bombardment

Boronization is a commonly used method of wall conditioning in fusion reactors. The application of boron films to the plasma-facing materials results in enhanced plasma performance due to the reduction of intrinsic impurities. This is primarily driven by a reduction in oxygen content that is chemically trapped in the boron film. The reactive nature of these boron films also raises questions concerning interactions with hydrogen isotopes. In this work, boron-deuterium interactions were studied using molecular dynamics (MD) with reactive force field potentials. An amorphous boron substrate was irradiated by D atoms at varying incident ion energies (10 eV < E_i < 150 eV) and angles (0° < α < 85°). The reflection probability was calculated, and the result was compared to the output calculated by a binary collision approximation (BCA) code. This comparison found that BCA underestimated the reflection probability at E_i < 35 eV, and α > 45°. Sputtering of the substrate material was also studied. These results showed that chemical sputtering of B (BD, BD₂, BD₃) at low (<20 eV) incident deuterium energies is a significant effect. This result suggests that chemical sputtering could be a significant factor in limiting boron coating lifetime.