  The electronic structure of various (001), (110), and (111)B surfaces of
n-type InSb were studied with scanning tunneling microscopy and spectroscopy.
The InSb(111)B (3x1) surface reconstruction is determined to be a disordered
(111)B (3x3) surface reconstruction. The surface Fermi-level of the In rich and
the equal In:Sb (001), (110), and (111)B surface reconstructions was observed
to be pinned near the valence band edge. This observed pinning is consistent
with a charge neutrality level lying near the valence band maximum. Sb
termination was observed to shift the surface Fermi-level position by up to
$254 \pm 35$ meV towards the conduction band on the InSb (001) surface and $60
\pm 35$ meV towards the conduction band on the InSb(111)B surface. The surface
Sb on the (001) can shift the surface from electron depletion to electron
accumulation. We propose the shift in the Fermi-level pinning is due to charge
transfer from Sb clusters on the Sb terminated surfaces. Additionally, many
sub-gap states were observed for the (111)B (3x1) surface, which are attributed
to the disordered nature of this surface. This work demonstrates the tuning of
the Fermi-level pinning position of InSb surfaces with Sb termination.
