Improved thermoelectric performances of nanocrystalline Sb2Te3/Cr bilayers by reducing thermal conductivity in the grain boundaries and heterostructure interface

Abstract

Nanocrystalline Sb2Te3/Cr bilayers with varying Cr layer thicknesses were prepared with the aim of improving thermoelectric performances. Prior to the deposition of Sb2Te3 films, Cr layers with thicknesses ranging from 0 to 116 nm were deposited on glass substrates. The cross-sectional morphologies of the Sb2Te3/Cr bilayers showed that the Cr layer was tightly connected to both the Sb2Te3 film and the substrate. The highest power factor of 9.1 μW/(cm·K2) was obtained for the single Sb2Te3 film, while the lowest thermal conductivity (measured using the 3ω method) of 0.75 W/(m·K) was recorded for the Sb2Te3/Cr bilayer with a Cr layer thickness of 73 nm. This was attributed to combined phonon scattering on the grain boundaries of the nanocrystalline Sb2Te3 films and the heterostructure interface between the Sb2Te3 film and the Cr layer. The highest figure-of-merit (ZT = 0.28) was achieved for the Sb2Te3/Cr bilayer (Cr = 73 nm), while the single Sb2Te3 film gave a ZT of 0.11. We conclude that the thermoelectric performance of the nanocrystalline Sb2Te3/Cr bilayers could be improved by introducing a Cr layer of an appropriate thickness.