Multi-quantum-well structures of Bi2Te3 are predicted to have a high thermoelectric figure of merit ZT. Bi2Te3 thin films and Bi2Te3∕Bi2(Te0.88Se0.12)3 superlattices (SLs) were grown epitaxially by molecular beam epitaxy on BaF2 substrates with periods of 12 and 6nm, respectively. Reflection high-energy electron diffraction confirmed a layer-by-layer growth, x-ray diffraction yielded the lattice parameters and SL periods and proved epitaxial growth. The in-plane transport coefficients were measured and the thin films and SL had power factors between 28 and 35μW∕cmK2. The lattice thermal conductivity varied between 1.60W∕mK for Bi2Te3 thin films and 1.01W∕mK for a 10nm SL. The best figures of merit ZT were achieved for the SL; however, the values are slightly smaller than those in bulk materials. Thin films and superlattices were investigated in plan view and cross section by transmission electron microscopy. In the Bi2Te3 thin film and SL the dislocation density was found to be 2×1010cm−2. Bending of the ...

Structural and thermoelectric properties of epitaxially grown Bi2Te3 thin films and superlattices

We report on an enhanced thermoelectric figure of merit ZT=σS2T/λ (where σ is electrical conductivity, S is thermopower, T is absolute temperature, and λ is thermal conductivity) for PbTe/PbSe0.20Te0.80 superlattices (SLs) and PbTe doping SLs due to a reduction of the thermal conductivity λ parallel to the layer planes. Despite a small decrease of the power factors σS2 due to a reduction of σ in these superlattices, the figure of merit is higher as compared to the corresponding bulk materials and reaches maximum values in the temperature range between 400 and 570 K.

PbTe based superlattice structures with high thermoelectric efficiency

Experimental evidence is presented for an enhanced thermoelectric figure of merit ZT=σS2T/λ (where σ is the electrical conductivity, S the thermopower, T the temperature, and λ is the thermal conductivity) by a reduction of the thermal conductivity λ in PbTe- and Bi2Te3-superlattices (SLs) parallel to the layer planes. Data on thermoelectric properties of Bi2Te3/Bi2(SexTe1−x)3-SLs, of PbTe-based doping SLs, and PbTe/PbSe0.2Te0.8-SLs are presented. In these structures, a decrease of λ was measured compared to the corresponding bulk compounds or homogeneous alloys. Despite a drop of the total power factor σS2 in the SLs in total an enhancement of the figure of merit ZT is found in these highly-doped PbTe and Bi2Te3-based SLs.

High thermoelectric figure of merit ZT in PbTe and Bi2Te3-based superlattices by a reduction of the thermal conductivity

A radiation thermopile made of p-(Bi 1− x Sb x ) 2 Te 3 and n-Bi 1− x Sb x films is presented. The technological steps

F. Völklein

Papers

Methods for the measurement of thermal conductivity and thermal diffusivity of very thin films and foils

Multijunction thin-film radiation thermopile sensors