Photoconduction and the electronic structure of silica nanowires embedded with gold nanoparticles

Abstract

Silica nanowires (SiO${}_{x}$-NWs) embedded with Au peapods have been studied by energy-filtered scanning transmission electron microscopy (EFTEM), O $K$- and Au ${L}_{3}$-edge x-ray absorption near-edge structure (XANES), and extended x-ray absorption fine structure (EXAFS), x-ray emission spectroscopy (XES) and scanning photoelectron microscopy. XANES and XES data show that band gaps of Au-peapod-embedded and pure SiO${}_{x}$-NWs were 6.8 eV. In additional, XANES and EXAFS results indicate illumination-induced electron transfer from Au peapod to SiO${}_{x}$-NWs and does not show any feature attributable to the formation of Au-Si bonding in the Au peapod embedded in SiO${}_{x}$-NWs with or without illumination. Photoresponse and EFTEM measurements show that green light has more significant enhancement of photoconductivity than red and blue light due to surface plasmon resonance and suggest that transport of electrons across SiO${}_{x}$-NWs is via Mott-variable-range hopping mechanism through localized or defect states.