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II. EXPERIMENTAL DETAILS A. Synthesis of Ag NWsSynthesis of Ag NWs has been carried out by various procedures, such as template based 14,15 and soft solution methods. 16,17 Here, the Ag NWs were synthesized by reducing silver nitrate (AgNO 3 ) with ethylene glycol (EG) in presence of copper dichloride dihydrate (CuCl 2 + 2 H 2 O) and polyvinylpyrrolidone (PVP). The EG is used as solvent and reducing agent whereas the PVP is used as capping agent. 18 In the beginning, 10 mL of EG (Sigma-Aldrich, anhydrous 99.8 %) was heated in an oil bath at 151.5 ○ C for 1 h under continuous magnetic stirring at 260 rpm. Then, 80 µL of a 4 mM CuCl 2 + 2 H 2 O (Sigma-Aldrich, 99.999 %)/EG solution was added to the preheated EG and stirred for another 15 min. Next, 3 mL of 0.282 mM PVP (Sigma-arXiv:1410

Low-field magnetotransport measurements of topological insulators such as Bi2Se3 are important for revealing the nature of topological surface states by quantum corrections to the conductivity, such as weak-antilocalization. Recently, a rich variety of high-field magnetotransport properties in the regime of high electron densities (∼1019 cm−3) were reported, which can be related to additional two-dimensional layered conductivity, hampering the identification of the topological surface states. Here, we report that quantum corrections to the electronic conduction are dominated by the surface states for a semiconducting case, which can be analyzed by the Hikami-Larkin-Nagaoka model for two coupled surfaces in the case of strong spin-orbit interaction. However, in the metallic-like case this analysis fails and additional two-dimensional contributions need to be accounted for. Shubnikov-de Haas oscillations and quantized Hall resistance prove as strong indications for the two-dimensional layered metallic behavior. Temperature-dependent magnetotransport properties of high-quality Bi2Se3 single crystalline exfoliated macro and micro flakes are combined with high resolution transmission electron microscopy and energy-dispersive x-ray spectroscopy, confirming the structure and stoichiometry. Angle-resolved photoemission spectroscopy proves a single-Dirac-cone surface state and a well-defined bulk band gap in topological insulating state. Spatially resolved core-level photoelectron microscopy demonstrates the surface stability.

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