Thickness-dependent bulk properties and weak antilocalization effect in topological insulator Bi₂Se₃

We show that a number of transport properties in topological insulator (TI) Bi₂Se₃ exhibit striking thickness dependences over a range of up to five orders of thickness (3 nm-170 μm). Volume carrier density decreased with thickness, presumably due to diffusion-limited formation of selenium vacancies. Mobility increased linearly with thickness in the thin film regime and saturated in the thick limit. The weak antilocalization effect was dominated by a single two-dimensional channel over two decades of thickness. The sublinear thickness-dependence of the phase coherence length suggests the presence of strong coupling between the surface and bulk states.