Control of Surface Migration of Gold Particles on Si Nanowires

Abstract

On the surface of silicon nanowires (SiNWs) synthesized by gold (Au)-catalyzed chemical vapor deposition (CVD), Au particles 5-20 nm in diameter are formed if the growth conditions are within a specific range. We studied the mechanism of Au particle formation by growing SiNWs under different conditions, specifically by dynamically changing the growth parameters during the growth process. We show that insufficient supply of Si source to the Au-Si eutectic on top of the SiNWs enhances the migration of Au atoms on the surface of SiNWs in the form of Au-Si eutectic, which is precipitated on the surface as Au particles during cooling. We also show that using Au-Si eutectic on the surface of SiNWs as a catalyst enables one-step growth of branched SiNWs.

Growth of one-dimensional Si/SiGe heterostructures by thermal CVD

“…This was also observed on high magnification SEM images of pure Si nanowires, with sometimes new catalytic growth of very slender nanowires (figure S1 available at stacks.iop.org/Nano/19/335603). Despite some recent investigation on the surface migration of gold during the synthesis, this phenomenon remains unclear, and it is undoubtedly experimental conditions dependent [26][27][28][29]. However, for electronic or thermoelectric applications, gold can be easily removed from the nanowires by chemical gold removers [30].…”

Volume 1534 (Symposium 6B)

“…The composition of the additional main segment and the small whiskers was found by high resolution TEM to be pure Si with wurtzite structure, although the preceding NW segment was SiGe. In the second case, see Figure 1-b, the region of the single SiGe NW located near the droplet appears decorated with Au small drops due to unwanted Au diffusion on the NW sidewalls during the growth stop stage of the process [9]. Growth continues further from the main droplet due to the presence of residual gases inside the chamber, in most cases in the same direction than the preceding NW segment, being this additional section also pure Si with wurtzite structure.…”

Quantitative Testing of Robustness on Superomniphobic Surfaces by Drop Impact

“…The SiO 2 layer ensures a relative disorder in the diagonal direction of the NWs growth. The orientation is also influenced by the pressure prescribed during the VLS process [25]: the orientation varies from about 30 • to 90 • with respect to the horizontal: the larger the pressure is, the straighter the NWs grow (with also a narrower distribution of orientation).…”