1 research outputs found
Ambipolar Surface State Thermoelectric Power of Topological Insulator Bi<sub>2</sub>Se<sub>3</sub>
We measure gate-tuned thermoelectric
power of mechanically exfoliated
Bi<sub>2</sub>Se<sub>3</sub> thin films in the topological insulator
regime. The sign of the thermoelectric power changes across the charge
neutrality point as the majority carrier type switches from electron
to hole, consistent with the ambipolar electric field effect observed
in conductivity and Hall effect measurements. Near the charge neutrality
point and at low temperatures, the gate-dependent thermoelectric power
follows the semiclassical Mott relation using the expected surface
state density of states but is larger than expected at high electron
doping, possibly reflecting a large density of states in the bulk
gap. The thermoelectric power factor shows significant enhancement
near the electron–hole puddle carrier density ∼0.5 ×
10<sup>12</sup> cm<sup>–2</sup> per surface at all temperatures.
Together with the expected reduction of lattice thermal conductivity
in low-dimensional structures, the results demonstrate that nanostructuring
and Fermi level tuning of three-dimensional topological insulators
can be promising routes to realize efficient thermoelectric devices