The nanorod arrays were fabricated in a custom designed
electron-beam deposition system (Torr International, Inc.) [13,33].
Fe2O3 nanorods was first deposited onto Si and/or glass substrates
with the incident angle = 86◦, with the substrate rotating
azimuthally at 0.5 rev/s. The deposition proceeded until a nominal
thickness of 3 m, as determined by a quartz crystal
microbalance (QCM), was achieved. Based on the nanorod separation
and height measured using scanning electron microscopy,
the vapor incident angle for the TiO2 shell deposition was determined
to be = 6.1◦. Further details describing this calculation
and the GLAD core–shell deposition method can be found in
Ref. [13]. Using the same substrate azimuthal rotation rate of
0.5 rev/s, the TiO2 shell was deposited to a nominal thickness of
50 nm. The as-deposited Fe2O3–TiO2 nanorod samples were then
annealed in a quartz tube furnace (Lindberg/Blue M Company) in
open air for 3 h, at different preset temperatures from 350 ◦C to
750 ◦C.
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