Advanced VLS growth of gold encrusted silicon nanowires Mediated by porous Aluminium Oxide template

Abstract

Abstract A highly efficient technique for the generation of dense and homogeneous Au-nanodroplets using Anodic Aluminium Oxide template (AAO) for the fabrication of single crystal gold encrusted array of silicon nanowires (SiNWs) was successfully developed. In interest of extending AAO's practical applicability, the Au-thin film sandwiched between Si-substrate and AAO was torn-up into small nanodroplets at annealing temperature followed by removal of AAO template before VLS growth instead of growing SiNWs directly in presence of AAO template. It's observed that smaller Au-nanodroplets are mandatory to yield dense array of SiNWs, further, size of formed Au-droplets is directly relied on AAO pore-size. Thus, construction of desired pore diameter on AAO was critically controlled by the application of voltage in presence of different etchants (sulfuric acid (SA), oxalic acid (OA) and phosphoric acid (PA)). Among the different etchants used SA demonstrated smaller AAO-pore size at a specific voltage and concentration. Further, obtained smaller Au-nanodroplets (from SA etched AAO) exhibited a denser array of SiNWs on VLS growth at particular set of experimental conditions. Characterization by advanced techniques such as UV–Vis spectroscopy, Micro-Raman spectroscopy, Scanning Electron Microscope (SEM), Transmission Electron Microscopy (TEM), High-Angle Angular Dark Field Scanning Transmission Electron Microscopy (HAADF-STEM) and Energy Dispersive X-ray Spectroscopy (EDX) revealed that the formed SiNWs were of 199 ± 43 nm diameter with well-decorated gold nano encrustations on the surface and at the tip. The formed SiNWs were in resemblance with SiNWs obtained from high precision e-beam Lithography, evidencing the superiority of the current method.