Figure 6.

(a) Hall resistance against magnetic field for ${\mathrm{Bi}}_2{\mathrm{Se}}_3$ films with different thicknesses (indicated in QLs on the right part of the plot) showing the non-linear dependence. (b) Carrier densities obtained from the SdH oscillations against thickness. (c) Mobilities obtained from the two-band analysis against thickness. In (b) and (c), the blue circles represent the bulk data $\left({\mathrm{n}}_{\mathrm{b}},{\mathsf{\mu }}_{\mathrm{b}}\right)$ and the red squares represent the surface data $\left({\mathrm{n}}_{\mathrm{s}},{\mathsf{\mu }}_{\mathrm{s}}\right)$, where empty and filled squares represent the two different surfaces. (d) ${\mathrm{G}}_{\mathrm{s}}/{\mathrm{G}}_{\mathrm{tot}}$ against film thickness. (e) 2D Magnetoconductance for different film thicknesses. (f) Value of $\mathsf{\alpha }$ against film thickness. Inset in (e) shows schematic energy bands above and below the critical thickness. Data were taken at $\mathrm{T}=1.6\mathrm{K}$. Reprinted with permission from Reference [13]. Copyright 2012 American Physical Society.