  We describe a catalyst-free vapor-solid synthesis of bismuth selenide
(Bi2Se3) nanostructures at ambient pressure with hydrogen as a carrier gas. The
nanostructures were synthesized on glass, silicon and mica substrates and the
method yields a variety of nanostructures: nanowires, nanoribbons,
nanoplatelets and nanoflakes. The materials analysis shows high chemical purity
in all cases, without sacrificing the crystalline structure of Bi2Se3.
Low-temperature measurements of the nanostructures indicate contributions from
the surface states with a tunable carrier density. Samples synthesized on
flexible mica substrates show no significant change in resistance upon bending,
indicating robustness of as-grown Bi2Se3 nanostructures and their suitability
for device applications.
