Low-temperature vapour–liquid–solid (VLS) growth of vertically aligned silicon oxide nanowires using concurrent ion bombardment

Abstract

Vertically aligned silicon oxide nanowires can be synthesized over a large area by a low-temperature, ion-enhanced, reactive vapour-liquid-solid (VLS) method. Synthesis of these randomly ordered arrays begins with a thin indium film deposited on a Si or SiO(2) surface. At the processing temperature of 190 degrees C, the indium film becomes a self-organized seed layer of molten droplets, receiving atomic silicon from a DC magnetron sputtering source rather than from the gaseous precursors used in conventional VLS growth. Simultaneous vigorous ion bombardment aligns the objects vertically and expedites mixing of oxygen and silicon into the indium. Silicon oxide precipitates from each droplet in the form of multiple thin strands having diameters as small as 5 nm. These strands form a single loose bundle growing normal to the surface, eventually consolidating to form one nanowire. The vertical rate of growth can reach 300 nm min(-1) in an environment containing argon, hydrogen, and traces of water vapour. This paper discusses the physical and chemical factors leading to the formation of the nanostructures. It also demonstrates how the shape of the resulting nanostructures can be further controlled by sputtering, during both VLS growth and post-VLS processing. Key technological advantages of the developed process are nanowire growth at low substrate temperatures and the ability to form aligned nanostructure arrays, without the use of lithography or templates, on any substrate onto which a thin silicon film can be deposited.

Growth of silicon oxide nanowires at low temperature using tin hydroxide catalyst

“…One can thus say that growing at low temperature allows a better control of the shape and length of the SiO x nanowires. Similar alignment was already observed for SiO 2 nanowires growth using indium catalyst at temperature as low as 190 1C [27].…”

Silica nanowire–Au nanoparticle pea-podded composites: Synthesis and structural analyses

“…Amorphous SiO x NWs can be grown on a crystalline Si substrate by first depositing a thin metal film (Au, for example) on its surface and then heating the system to elevated temperatures (N1273 K) in an inert ambient (e.g. N 2 or Ar) containing trace amounts (3-5 ppm) of oxygen [2,3,[7][8][9][10][11][12][13][14][15]. Considering, for example, a thin Au film on the Si substrate, it is widely recognized [8,16] that, during the heating, the film breaks up into nanometer-scale islands and reacts with the Si substrate to form molten droplets of Au-Si eutectic composition (in fact, the Au/Si phase diagram has an eutectic point at 636 K corresponding to 18.6 at.% of Au, see Fig.…”

Study on the role of filament temperature on growth of indium-catalyzed silicon nanowires by the hot-wire chemical vapor deposition technique

“…It has an advantage as catalyst rather than gold for low temperature catalytic growth due to its low melting point (w157 C). In showed its ability to suit to a variety of deposition techniques including magnetron sputtering [29], ebeam evaporation [30], PECVD [31,32] and HWCVD [14] inpreparation of SiNWs. An initiation of vapor-liquid-solid (VLS) growth of SiNWs at substrate temperature as low as 240 C has been achieved using In catalyst and PECVD [32].However, the surface oxidation of the In catalyst could reduce its catalytic effect.…”