Induction of the surface plasmon resonance from C-incorporated Au catalyst in Si1−xCx nanowires

Abstract

Si 1Àx C x nanowires (NWs) were synthesized by varying the ratio of SiH 4 and CH 3 SiH 3 gases using a vapor-liquid-solid (VLS) procedure using Au as a catalyst. The growth rate of the Si 1Àx C x NWs and the change in the wire shape from straight to helical near the Au tip were found to be closely related to the ratio of the CH 3 SiH 3 content. The large concentration of C in the Si 1Àx C x NWs was proportional to the CH 3 SiH 3 content, overcoming the extremely low solubility of C in Si, resulting in an interstitial incorporation of C atoms in the wire. This incorporation can be attributed to the cleavage of Si-C bonds in the CH 3 SiH 3 compound through the Au catalyst (an Au-Si liquid-state cluster of about 70-100 nm) during wire growth by the VLS method. Simultaneously supplying CH 3 SiH 3 and SiH 4 gases enhanced the diffusion of Au atoms from the tip to the sidewall of the wire, while also deforming the shape of the Au tip. When the CH 3 SiH 3 gas was increased to 1.5 sccm, the number of Au nanoparticles (2-3 nm in size) at the lateral surface induced a surface plasmon resonance (SPR) and improved the optical conductivity (s) of the Si 1Àx C x NWs. For 2 sccm of CH 3 SiH 3 , a remarkable increase in the number of C atoms incorporated in the Au nanoparticles along the sidewall red shifted the SPR peak, suggesting that the SPR can be modulated by the Au-C interactions in the nanoparticles.

The effect of structural and chemical bonding changes on the optical properties of Si/Si1−xCx core/shell nanowires

“…We analyzed the chemical reaction and incorporation of C atoms into the Si lattice and observed interstitially incorporated C atoms in the Si NWs due to cleavage of the Si-C bond from the SiH 3 CH 3 precursor through the Au catalyst during wire growth. 11 Our result is very interesting because generally, it is well known that substitutional incorporation of C atoms into the Si lattice is stable compared to interstitial incorporation. 12,13 Based on previous results for Si 1Àx C x NWs, we attempted to synthesize Si/Si 1Àx C x CS NWs to avoid interstitial incorporation of C atoms while removing the Au catalyst before deposition of the Si 1Àx C x shell on the sidewall of the Si core NW.…”

“…The process conditions are well established for the vertical growth of Si NWs using this system. 11 Aer the Si NW growth, the Au tip at the top of the Si NWs was etched by using a KI-I 2 solution for the Si 1Àx C x growth and then rinsed in de-ionized (DI) water. The sample was introduced into the UHV-CVD chamber to deposit the Si 1Àx C x shell on the sidewall of the Si core NW by a CVD method.…”