Bismuth oxide (Bi<sub>2</sub>O<sub>3</sub>) is a multi-functional oxide semiconductor with various properties of interest such as high
reflective index, high photoconductive response, luminescence and high oxygen-ion conductivity, potentially useful as
optical coatings, electrodes of solid oxide fuel cells (SOFC), supercapacitors, visible-light activated photocatalysts, and
gas sensors. Large areas of bismuth oxide (Bi<sub>2</sub>O<sub>3</sub>) nanocones were grown onto Si(001) substrates by magnetron
sputtering. The samples were characterized by field emission scanning electron microscopy (FE-SEM), X-ray diffraction
(XRD), transmission electron microscopy (TEM), and photoluminescence (PL). The obtained tapered nanostructures
consist of high-density nanocones with diameters approximately 70–130 nm and lengths of 1–3 μm. XRD results reveal
that the Bi<sub>2</sub>O<sub>3</sub> nanocones can undergo a phase transition from the α to the β phase at growth temperatures over 450°C.
This phase transition was confirmed by TEM and PL. The growth mechanism of Bi<sub>2</sub>O<sub>3</sub> nanocones was identified as grain
boundary-assisted growth, in which a Bi seeding layer is crucial to the formation of the nanostructures. The results
herein suggest that introducing a surface seeding layer may provide an effective way to grow various 1D nanostructures
over large areas in high yield by magnetron sputtering.