Thickness-Independent Transport Channels in Topological Insulator Bi2Se3 Thin Films

With high quality topological insulator Bi2Se3 thin films, we report thickness-independent transport properties over wide thickness ranges. Conductance remained nominally constant as the sample thickness changed from 256 to similar to 8 QL(where QL refers to quintuple layer, 1 QL approximate to 1 nm). Two surface channels of very different behaviors were identified. The sheet carrier density of one channel remained constant at similar to 3.0 X 10(13) cm(-2) down to 2 QL, while the other, which exhibited quantum oscillations, remained constant at similar to 8 X 10(12) cm(-2) only down to similar to 8 QL. The weak antilocalization parameters also exhibited similar thickness independence. These two channels are most consistent with the topological surface states and the surface accumulation layers, respectively.