Nano-size silicon whiskers produced by chemical vapor deposition

Sponge type deposits composed of nanometer sized Si whiskers were formed on Davisil (porous SiO₂) gel substrates by chemical vapor deposition (CVD) using methyltrichlorosilane (MTS) as a precursor and H₂ as carrier gas. The diameters of the fine whiskers are estimated to be 100 nm or smaller from SEM observations. XRD analyses revealed that the coatings formed at 800 and 900°C contained microcrystalline Si and the Auger analysis indicated the existence of free carbon. The surface area of the coated Davisil was approximately 189 ± 5 m²/g, as obtained from BET measurements. The coatings were also applied on several other substrates, such as AlN and low surface area (< 224 m²/g) silica gel, with the same coating conditions. On these substrates, highly porous Si has also been observed on AlN substrates, and nonporous, half sphere shaped coatings were observed on low surface area silica gel substrates.