Thermoelectric properties of Bi2Te3 microwires

Abstract

AbstractWe present here a study of electrical and thermoelectric properties of n ‐ and p ‐Bi2Te3 microwires (n ‐type Bi2Te2Se; p ‐type Bi0.5Sb1.5Te3) with different diameters (d =10–20 µm). Cylindrical Bi2Te3 crystals with glass coating were prepared by the liquid phase casting in a glass capillary. The X‐ray studies have shown that the microwire core is in general polycrystal consisting of big disoriented single crystal blocks. Measurements of resistance and thermopower were carried out over a wide range of temperatures (4.2–300 K) and magnetic fields (0–14 T). At 300 K for samples of n ‐ and p ‐type the thermopower S and power factor P.f. = S2σ were (100–140) µV/K, 1.6×10‐3 W/(K2m) and (150–300) µV/K, 4.5×10‐3 W/(K2m), respectively. Magnetic field dependences of Power factor were measured at various temperatures (T =35, 100, 270 K) and different magnetic field orientations. A broad maximum is the dominant feature of the magnetic field dependence of power factor for p‐ type samples, while power factor decreases for n‐ type samples. We have obtained maximum power factor P.f. =6.8×10‐3 W/(K2m) for p ‐type sample at longitudinal magnetic field B =3 T at T =100 K. Shubnikov de Haas oscillations with equal periods ΔB =0.038 T‐1 both in longitudinal and transverse magnetic fields for carriers with mc = 0.15m0 in p ‐type Bi2Te3 microwire were observed. These oscillations could arise from the topological surface states. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)