Abstract
Free-standing tungsten-nanowhiskers about 3 nm in thickness were fabricated on SiO2 substrates with electron-beam induced deposition in a transmission electron microscope operated at 400 kV at room temperature. The growth process of the nanowhisker was observed in-situ and analyzed. The nanowhisker was characterized with high-resolution transmission electron microscopy. Nucleus-deposits smaller than 1 nm formed on the surface of the substrate, grew to 2∼3 nm and then grew out of the surface to form nanowhiskers under the electron irradiation. The nanowhisker grew long at its tip. The density and growth rate of the nanowhiskers were different at different places of the same substrate. A part of the nanowhiskers grew long to about 20 nm at the electron dose of 1.16×1025 e m−2 for an irradiation time of 223 s. The nanowhisker contained nanometer-sized grains of body-centred cubic structural tungsten and an amorphous part. It was found that there exists a critical size about 2–3 nm for a nucleus to grow to a nanowhisker. It is suggested that the nucleation site of the nanowhisker may be controlled by putting appropriate conductive particles in the critical size on the surface of an insulator substrate.
