RESUMO
The need for miniaturized and high-performance devices has attracted enormous attention to the development of quantum silicon nanowires. However, the preparation of abundant quantities of silicon nanowires with the effective quantum-confined dimension remains challenging. Here, we prepare highly dense and vertically aligned sub-5 nm silicon nanowires with length/diameter aspect ratios greater than 10,000 by developing a catalyst-free chemical vapor etching process. We observe an unusual lattice reduction of up to 20% within ultra-narrow silicon nanowires and good oxidation stability in air compared to conventional silicon. Moreover, the material exhibits a direct optical bandgap of 4.16 eV and quasi-particle bandgap of 4.75 eV with the large exciton binding energy of 0.59 eV, indicating the significant phonon and electronic confinement. The results may provide an opportunity to investigate the chemistry and physics of highly confined silicon quantum nanostructures and may explore their potential uses in nanoelectronics, optoelectronics, and energy systems.
RESUMO
The synthesis of controllable hollow graphitic architectures can engender revolutionary changes in nanotechnology. Here, we present the synthesis, processing, and possible applications of low aspect ratio hollow graphitic nanoscale architectures that can be precisely engineered into morphologies of (1) continuous carbon nanocups, (2) branched carbon nanocups, and (3) carbon nanotubes-carbon nanocups hybrid films. These complex graphitic nanocup-architectures could be fabricated by using a highly designed short anodized alumina oxide nanochannels, followed by a thermal chemical vapor deposition of carbon. The highly porous film of nanocups is mechanically flexible, highly conductive, and optically transparent, making the film attractive for various applications such as multifunctional and high-performance electrodes for energy storage devices, nanoscale containers for nanogram quantities of materials, and nanometrology.
