Development of Nanostructured Black Metal by Self-Growing Helium Bubbles for Optical Application

摘要

When tungsten is exposed to a helium plasma under specific conditions, fiberform nanostructures grow from the surface, and optical properties significantly alter. It is shown that the optical absorptivity increases significantly by the helium irradiation from visible to near-infrared wavelength range. The optical absorptivity became almost 100% from visible to near infrared wavelength range after the nanostructure was formed on the surface. The result indicates that the emissivity of radiation in visible and near infrared wavelength range also increases significantly by the helium irradiation. The emissivity around 1550 nm is 4.4 times higher than the initial value, while it is twice at the visible wavelength range. The helium fluence dependences of the specular and total optical reflectances and the morphology change observed by transmission electron microscope (TEM) are revealed.