Investigation of the optical properties and clues to the emission mechanism in silver nanoparticle–coated silicon nanowires.

This paper reports the effects of the silver nanoparticle (Ag-NP) deposition on the optical properties of silicon nanowire (SiNW) layer. Vertically, SiNW arrays were prepared in HF/AgNO3 aqueous solution using metal-assisted chemical etching of p-type silicon. The insertion of Ag particles in SiNWs was performed by electroless deposition method by varying the concentration of the silver nitrate solution. Scanning electron microscopy (SEM) micrographs show arrays of parallel nanowires as well as the presence of Ag-NPs on SiNWs layer. Fourier transform infrared (FTIR) and Raman spectroscopies reveal the existence of new vibration bands that are related to silver particles and their interactions with SiNW surface. By Raman spectroscopy, we also observed the manifestation of SERS effect for SiNWs/Ag composites. The optical properties of the elaborated samples were investigated by photoluminescence spectroscopy (PL). The integrated PL intensity of SiNWs was increased fourteen times by the deposition of silver nanoparticles on their surfaces for a silver nitrate concentration of 0.05 M which is essentially due to localized surface plasmon resonance. The PL spectrum of SiNWs/Ag exhibits intense emission band at 2.36–2.39 eV which is related to the interband and intraband transitions between the electronic states of Ag nanoparticles. Energy band diagram showing the emission mechanism in Ag/SiNWs composites was proposed. [ABSTRACT FROM AUTHOR]