In this study, a series of Bi 1.5 Sb 0.5 Te 1.7 Se 1.3 (BSTS) flakes 80-nm to 140-lm in thickness was fabricated to investigate their metallic surface states. We report the observation of surface-dominated transport in these topological insulator BSTS nanoflakes. The achievement of surface-dominated transport can be attributed to high surface mobility ($3000 cm 2 /V s) and low bulk mobility (12 cm 2 /V s). Up to 90% of the total conductance, the surface channel was estimated based on the

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... ss dependence of electrical conductance and the result of the Shubnikov-de Hass oscillations in a 200-nm BSTS. The nature of nontrivial Dirac surface states was also confirmed by the weak anti-localization effect. V C 2013 AIP Publishing LLC. [http://dx.