Taming tungsten fuzz

Kevin Woller


Wednesday, October 28, 2015



PSFC Student Seminars


A new variant of tungsten (W) nano-tendril “fuzz” has been observed for the first time in the Dynamics of ION Implantation and Sputtering Of Surface (DIONISOS) experiment, providing new insights to fuzz growth mechanisms. The new variation features discrete, isolated nano-tendril bundles distributed intragranularly, while the surfaces surrounding the bundles are free of large scale features. The structures are an important variation because instead of all plasma-wetted surface areas morphing into nano-tendrils, only a small fraction (<10%) of the surface has nano-tendril features. The macroscopic surfaces remain reflective, making microscopic inspection necessary for detection of the bundles. The largest bundles so far observed have dimensions of 10-20 microns transverse to the surface and reach longer dimensions of up to 70 microns normal to the material surface for helium (He) ion fluence on the order of 5x10^25 m^-2. Single nano-tendrils within the bundles are of similar dimension to standard fuzz, being approximately 10’s of nanometers in diameter. Isolated tendril features reach an extreme in that even single, free-standing whiskers have been observed with height to diameter aspect ratios of several hundred. Inter-bundle distances are several 10’s of microns, with the remaining surface surrounding the bundles laced with pinholes and nano-sized hillocks.