Catalyst proximity effects on the growth rate of Si nanowires

Si nanowires grown by the vapor-liquid-solid (VLS) mechanism were fabricated using Au-catalyst nanoparticles and silane (SiH4) gas on Si substrates. Au was deposited on the substrate surface both by electron-beam evaporation and Au-colloid deposition. Both kinking defects and vertical nanowire epitaxy on Si ⟨111⟩ substrates were found to be directly related to SiH4 flow rate. A correlation between Au-colloid dilution and the nanowire growth rate was also observed, with the growth rate increasing with increasing concentrations of Au-catalyst particles on the wafer surface. Systematic experiments relating the nanowire growth rate to the proximity of nearest-neighbor Au particles and Au reservoirs were carried out, and the results were found to be in good agreement with a SiH4 reaction model, which associates decomposition to form SiH2 with higher nanowire growth rates. Implications toward the realization of VLS-grown single nanowire transistors are discussed.