  The compound Bi14Rh3I9 has recently been suggested as a weak
three-dimensional topological insulator on the basis of angle-resolved
photoemission and scanning-tunneling experiments in combination with density
functional (DF) electronic structure calculations. These methods unanimously
support the topological character of the headline compound, but a compelling
confirmation could only be obtained by dedicated transport experiments. The
latter, however, are biased by an intrinsic n-doping of the materials surface
due to its polarity. Electronic reconstruction of the polar surface shifts the
topological gap below the Fermi energy, which would also prevent any future
device application. Here, we report the results of DF slab calculations for
chemically gated and counter-doped surfaces of Bi14Rh3I9. We demonstrate that
both methods can be used to compensate the surface polarity without closing the
electronic gap.
