Fabrication of self-standing nanowires, nanodendrites, and nanofractal-like trees on insulator substrates with an electron-beam-induced deposition

Self-standing tungsten nanowires, nanodendrites, and nanofractal-like trees were fabricated on insulator (Al₂O₃) substrates with a process of electron-beam-induced decomposition in a transmission electron microscope. The conditions for fabricating different morphologies are described. The fabricated structures are characterized with high-resolution transmission electron microscopy and X-ray energy-dispersive spectroscopy. A high concentration of tungsten and a high crystallinity of the structure are confirmed. The growth process is discussed, involving charges produced on the surface of the substrate and the behavior of precursor molecules under electron-beam irradiation. The formation of these structures is considered to relate to nanoscaled unevenness of the charge distribution on the surface of the substrate, movement of charges to the convex surface of the substrate, and accumulation of charges at the tips of the grown structures.