  We have systematically investigated the annealing effect on the structure and
composition of the polar surface of SrTiO3 (111), starting with an ex-situ
chemical etch. The relative surface concentration between Ti and Sr strongly
depends on both the annealing temperature and the oxygen processing. There is a
critical annealing temperature at which the maximum concentration ratio of Ti
to Sr is achieved, while still maintaining a (1 x 1) surface structure. We
demonstrate that with proper processing it is possible to avoid surface
reconstruction over a broad temperature range. Our results provide an optimal
temperature window for epitaxial film growth.
