Terahertz Emission from Vertically-aligned Silicon Nanowires

Abstract

AbstractLarge-area vertically aligned silicon nanowire (Si NW) arrays were synthesized with a controlled length (0.3 ˜ 9 μm) by the chemical etching of n-type silicon substrates. Upon their excitation using a fs Ti-sapphire laser pulse (800 nm), their THz emission intensity exhibits strong dependence on their length; the intensity increases sharply up to a length of 3 μm and then decreases slightly, due to the complete absorption of the optical pump power. The Raman scattering spectrum exhibits the same behavior as that of the THz emission. We suggest that the field enhancement by localized surface plasmons induces more efficient THz emission or Raman scattering for the longer Si NWs. The photocurrent measured in a photoelectrochemical cell showed consistently the length dependence with a maximum value at the length of 5 μm.