(J-362) On the Frits: An Approach Toward High-yield Silicon Nanowire Synthesis

Introduction:: Silicon nanomaterials such as large-area 2D membranes and 1D nanowires (NWs) are particularly useful in biological applications. Silicon NWs in particular show promise as a sensitive, highly-localized platform for biosensing. However, the yield of silicon NWs is low in conventional growths that proceed on planar, solid surfaces. We hypothesized that increasing the surface area of the growth substrate would improve from yield, with the caveat that porous substrate could limit gas diffusion, and therefore NW growth. As proof-of-concept, we demonstrated NWs growth inside a inside a glass frit substrate.


Materials and Methods:: We achieved NW growth in a home-built chemical vapor deposition (CVD) system that enabled independent control over temperature, pressure and gas composition. Porous glass frits, were obtained from Robu, grade 00. These were coated with poly-L-lysine (Sigma) at room temperature, which was pipetted on and left to set for two minutes. Afterwards, the poly-L-lysine was gently rinsed with deionized water (18 MΩ) and dried with a gentle flow of nitrogen. 20-nm gold nanoparticles (Ted Pella) were pipetted on and left to set for five minutes, after which the samples were similarly rinsed and dried. Subsequently, the samples were inserted into the CVD system, which was ramped up to 440-460°C over 15-45 minutes. p-type Si NW growth as achieved by flowing H₂, SiH₄ and B₂H₆ gasses with Si:B ratios ranging between 4000:1 and 500:1. NWs inside the frit were imaged by optical microscopy. NWs released from the growth substrate were characterized by TEM.





Results, Conclusions, and Discussions:: Results
Optical microscopy confirmed NW growth throughout the pore structure, confirming our hypothesis that large pores would not restrict flow significantly. TEM revealed single-crystalline NWs with ca. 20-nm diameters, similar to that of the gold nanoparticle catalyst, although overcoating was achieved at higher temperatures and pressures. The length of the the NWs could be tuned between 5 and 50 μm by adjusting the growth time.

Conclusions
Porous glass materials are a suitable material for Si NW growth, and could enable high-yield synthesis suitable for producing nanocomposite materials (e.g. 3D NW-embedded polymer scaffolds), or large-area nanoelectronic systems.


Acknowledgements (Optional): : We acknowledge an NSF CAREER grant (2239557) to BPT.

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