Impurity Effect on Weak Antilocalization in the Topological Insulator Bi2Te3

We study the weak antilocalization (WAL) effect in topological insulator Bi2Te3 thin films at low temperatures. The two-dimensional WAL effect associated with surface carriers is revealed in the tilted magnetic field dependence of magnetoconductance. Our data demonstrate that the observed WAL is robust against deposition of nonmagnetic Au impurities on the surface of the thin films, but it is quenched by the deposition of magnetic Fe impurities which destroy the pi Berry phase of the topological surface states. The magnetoconductance data of a 5 nm Bi2Te3 film suggests that a crossover from symplectic to unitary classes is observed with the deposition of Fe impurities.