(Bi1−xSbx)2Se3 thin films were prepared by molecular beam epitaxy (MBE). The existence of strong and robust topological surface states was demonstrated in the (Bi1−xSbx)2Se3 ternary system by angle-resolved photoemission spectroscopy (ARPES). The sheet carrier density n2D was found to be decreased by 75% by doping Sb into Bi2Se3, compared with that in the case of undoped Bi2Se3. The enhancement of the surface state transport due to Sb doping was also revealed via the high-field Hall effect and weak antilocalization measurement. Our results reveal the potential of this system for the study of tunable topological-insulator based device physics.

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