Dynamic growth process of W-nano-branched structure on insulator substrate studied with transmission electron microscopy

Controllable fabrication of nanostructure is important and necessary to application of nanomaterials in technology. Among the methods of fabrication of nanostructures, electron-beam-induced deposition (EBID) is a promising method. A transmission electron microscope (TEM), JEM-2010F operated at 200 kV, was used for fabrication of nanowires and nano-branched structures. Thin film samples Of SiO/sub 2/ or Al/sub 2/O/sub 3/ were used as substrates. Tungsten hexacarbonyl (W(CO)/sub 6/) powder was used as a precursor. The base pressure in column is lower than 2 /spl times/ 10/sup -5/ Pa. A gas introducing system which has a nozzle with an inner diameter smaller than 0. 1 mm and a reservoir of powder gas-source was used. The fabricated structures were characterized in-situ or after the fabrication with JEM-2010F TEM. All the experiments were performed at room temperature. Nanowires in diameter of about 3 nm nucleate on surface of substrate after starting the electron irradiation with intensity lower than 0.75 A/cm/sup 2/. They nucleate and grow within the all area electron beam irradiated. They grow almost normally to the surface of the substrate with distances of several nanometers between each other.