Is there a way to directly, here I means in real space, observe the interaction of the surface states of 3D topological insulators with defects (dopings and adatoms)? How to observe the spin texture of these surface states? Is there any experimental proposal for this?
Take a look at this paper http://arxiv.org/abs/1107.3747. It describes one rather particular case: the boundary of the graphene sheet. However, they should cite other works in this direction and be cited by others.
Lorentz force microscopy, magnetic force microscopy (MFM) or scanning Kerr microscopy should work.