TiO2/SiOx core-shell nanowires generated by heating the multilayered substrates

By heating Au/TiN/Si substrates, we fabricated TiO2/SiOx core-shell nanowires. By changing the thickness of predeposited Au layers, we demonstrated that the thickness of the Au layer needs to be optimized to obtain nanowires. High-resolution transmission electron microscopy image, X-ray diffraction spectrum, and selected area electron diffraction pattern coincidentally revealed that the resultant core nanowires had a tetragonal rutile structure of TiO2, and the shell was comprised of amorphous SiOx. The dominant growth mechanism was a base-growth mode, in which Au played a catalytic role, resulting in morphological changes with variation of the Au layer thickness. The TiO2/SiOx core-shell nanowires exhibited a broad photoluminescence emission band, which comprised four peaks centered at 1.54, 2.34, 2.67, and 2.99 eV, respectively. We expected that the 1.54 eV- and 2.34 eV-centered peaks arised from the TiO2 core, whereas the 2.67 eV- and 2.34 eV-peaks were ascribed to both the TiO2 core and the SiOx shell.