Polarized light microscopy of chemical-vapor-deposition-grown graphene on copper

Linearly polarized light microscopy (PM) revealed that graphene grown by chemical vapor deposition (CVD) on stepped Cu substrate may appear colored. The coloration is associated with the coupling of the light of 450-600 nm into propagating mode in the graphene layer when the electric vector (E →) of polarized light is parallel with the step edges and with the scattering when the E → is normal to the step edges. PM is an inexpensive, fast, and contamination free method to efficiently visualize graphene and to map the step structure of Cu substrates used for large area CVD growth of graphene. © 2012 American Institute of Physics

Nanotechnology of nanotubes and nanowires: From aligned carbon nanotubes to silicon oxide nanowires

Laser etching of Co, Ni and Fe films, in conjunction with the pyrolysis of solid organic precursors (e.g. aminodichlorotriazine, melamine, etc.) generates aligned carbon nanotube bundles and films of uniform length (< 200 mu m) and diameter (30 Angstrom - 80 Angstrom). However, nanotube alignment strongly depends upon laser etching conditions (e.g. laser power, pulse duration and focus distance). Additionally, condensed-phase techniques, using mixtures of molten LiCl and soft metals (e.g. Bi, Pb, etc.) as electrolytes, generate high yields of metallic nanowires (< 45 % overall material and < 2 mu m in length, < 100 nm OD). Finally, it is shown that novel 3-D flower-like silica nanostructures are produced by a simple and surprising solid-phase approach. It is observed that single catalytic nanoparticles act as nucleation sites, leading to unusual morphologies of silicon oxide nanofibres (20-120 nm OD and < 200 mu m). The latter structures may be useful in the context of catalysis, 3-D composite materials, and optoelectronic devices, thus breaking new ground in nanowire and nanofibre technology