Growth origin of large-scale fiberform nanostructures in He-W co-deposition environment

When tungsten (W) is deposited with helium (He) plasma (He-W co-deposition) on W surface, enhanced growth of fiberform nanostructure (fuzz) occurs, and sometimes it grows into large-scale fuzzy nanostructures (LFNs) thicker than 0.1~mm.In this study, different numbers of mesh openings (apertures) and W plates with nanotendril bundles (NTBs), which are tens of micrometers high nanofiber bundles, were used to investigate the condition for the origin of the LFN growth.It was found that the larger the mesh openings, the larger the area where LFNs are formed and the faster the formation tends to be. On NTB samples, it was found that NTBs grew significantly when exposed to He plasma with W deposition, especially when the size of the NTB reached $\sim$0.1~mm. The concentration of the He flux due to the distortion of the shape of the ion sheath is proposed as one of the reasons to explain the experimental results.