Thickness dependence of electrical conductivity and thermo-electric power of Bi_2.0Te_2.7Se_0.3/Bi_0.4Te_3.0Sb_1.6 thermo-electric devices

The electrical and thermo-electric (TE) properties of the bismuth telluride (BiTe)-based two-dimensional (2D) thermoelectric (TE) devices with different thin film thicknesses are analyzed systematically. The studied thin film thicknesses are covered from 100 nm to 400 nm. The accurate measured systems for the Seebeck coefficient (S) and electrical conductivity (σ) extractions are also built up in this work. When the thickness of the BiTe-based thin film in the TE device is scaled from 400 nm to 100 nm, the occurred optimized temperature (T) for the highest S value in these devices is found to be shifted from 60°C to 100°C. On the other hand, the best σ is observed in the thinner (100 nm) BiTe-based thin film devices under the higher T (130°C). Based on the understanding of S and σ values, the power factor and the figure of merit (ZT)-i.e., the ability of a TE material to efficiently produce electricity- A re also investigated further. Compared with the commercial bulk BiTe TE device, we demonstrate that the ZT value can be improved ∼50% with the thinner (100 nm) BiTe-based thin film devices in the higher T (>100°C) region.