CATALYTIC SYNTHESIS AND GROWTH MECHANISM OF TUNGSTEN NANOWIRE ARRAYS ON SiO2 SUBSTRATES

Single-crystalline W nanowires, with approximately 150 nm in diameter and 15 mu m in length, have been successfully synthesized on SiO2 substrates by chemical vapor deposition (CVD) with the assistance of Ni catalysts at 950 degrees C. The catalysts located at the tip of W nanowires were found to be Ni4W in a solid state, rather than a liquid state. The low-temperature growth of W nanowires using the solid catalysts can be generally accessible, provided that the appropriate combination of solid catalysts and nanowires are thermodynamically available, thus suggesting the implication for the potentially large-area integrated growth on various substrates. The growth direction of the generated [100]-oriented W nanowires was presumed to be determined by the orientation relationship between the solid Ni catalyst particle and the W precipitate. A possible catalytic growth model was proposed according to the analysis of the experimental results. The orientation relationship between the solid catalyst particle and the corresponding nanowire was expected to be also valid for some other nanowires induced by solid catalyst.