Silicon-Catalyzed Growth of Amorphous SiOx Nanowires by Laser Vaporization of Si and Si/SiO2

Abstract

Products from the laser vaporization of targets of four types—Si, (1:1) Si/SiO2, (1:9) Si/SiO2, and SiO2—without the addition of any metal catalysts in the presence of high-pressure (0.9 MPa) Ar gas were characterized by transmission electron microscopy (TEM), high-resolution TEM, energy-filtered TEM, transmission electron diffractometry, energy-dispersive X-ray spectroscopy, electron energy loss spectroscopy, and powder X-ray diffractometry. Amorphous SiOx (0.8 ≤ x ≤ 2.0) nanowires (NWs) (10–40 nm in diameter and up to 1 μm long), having crystalline Si nanoparticles (NPs) covered with thin amorphous SiOx layers at the NW tips, were observed for the products from the Si and Si/SiO2 composite targets, while only amorphous SiOx NPs were produced from the SiO2 target. The O content relative to that of the Si in SiOx NWs was also increased with increasing the content of SiO2 in the targets. We propose a novel mechanism for the growth of amorphous SiOx NWs, in which nuclei of the NWs are formed on the Si-rich ...