  Interfaces between exfoliated topological insulator Bi2Se3 and several
transition metals deposited by sputtering were studied by XPS, SIMS, UPS and
contact I-V measurements. Chemically clean interfaces can be achieved when
coating Bi2Se3 with a transition metal layer as thin as 1 nm, even without
capping. Most interestingly, UPS spectra suggest depletion or inversion in the
originally n-type topological insulator near the interface. Strong band bending
in the topological insulator requires careful material engineering or electric
biasing if one desires to make use of the spin locking in surface states in the
bulk gap for potential spintronic applications
