Implantation of Gallium into Layered WS 2 Nanostructures is Facilitated by Hydrogenation.

Bombarding WS 2 multilayered nanoparticles and nanotubes with focused ion beams of Ga + ions at high doses, larger than 10 16 cm -2 , leads to drastic structural changes and melting of the material. At lower doses, when the damage is negligible or significantly smaller, the amount of implanted Ga is very small. A substantial increase in the amount of implanted Ga, and not appreciable structural damage, are observed in nanoparticles previously hydrogenated by a radio-frequency activated hydrogen plasma. Density functional calculations reveal that the implantation of Ga in the spaces between adjacent layers of pristine WS 2 nanoparticles is difficult due to the presence of activation barriers. In contrast, in hydrogenated WS 2 , the hydrogen molecules are able to intercalate in between adjacent layers of the WS 2 nanoparticles, giving rise to the expansion of the interlayer distances, that in practice leads to the vanishing of the activation barrier for Ga implantation. This facilitates the implantation of Ga atoms in the irradiation experiments.