Porous tungsten nanostructure formation using a helium arc discharge plasma under sub-atmospheric pressure

• Published in: Journal of physics. D, Applied physics Applied physics, 2019-07, Vol.52 (37), p.375201
• Main Authors: Kikuchi, Yusuke, Okumura, Takuya, Kadowaki, Kazumasa, Aota, Tatsuya, Maenaka, Shiro, Fujita, Kazunori, Takamura, Shuichi
• Format: Article
• Language: English
• Subjects: helium arc plasma irradiation; helium bubble; nanoparticle network; porous tungsten nanostructure
• ISSN: 0022-3727; 1361-6463
• DOI: 10.1088/1361-6463/ab2ac1

Porous tungsten (W) nanostructure formation was performed for the first time using a helium (He) arc discharge plasma under sub-atmospheric pressure of 80 kPa. Scanning electron microscope observations showed that micron-sized bubble and hole structures were formed in the W substrate at a surface temperature of 1700 °C, indicating He penetration into the W substrate. At the surface temperature of 800 °C, surface blackening of the W substrate due to the He plasma irradiation for two hours was found. The unique surface morphology has a W nanofiber network with a thickness of ~10 µm which consists of assembly of W nanoparticles with a diameter of 20-30 nm. It was suggested that an interaction between W vapor evaporated from the W electrodes and the surrounding He plasma plays a key role for physical processes of the nanostructured W formation identified in this study. It could be formed due to a process of cluster-cluster aggregation of W nanoparticles produced by nucleation and condensation from the W vapor phase. The W nanoparticle network deposition is considered to be a new process for the porous W nanostructure formation as an alternative to standard fuzz formation associated by bubble formation on the surface of base W substrate.