Effect of thermal annealing on thermoelectric properties of BixSb2-xTe3 thin films grown by sputtering

摘要

The present study focuses on the enhancement of the Seebeck coefficient (S) of BiSbTe alloy thin films on post-deposition annealing. It is demonstrated that thermal treatment leads to about twofold enhancement in the S of BiSbTe alloy thin films deposited using DC magnetron sputtering. Investigation of the enhanced thermoelectric properties has been done by studying their phase, compositional, and structural properties. The x-ray diffraction patterns show the presence of a mixed BixSb2-xTe3 phase, which crystallizes in the Sb-rich phase on annealing. The surface morphology of the as-deposited samples exhibit spherical features that grow in the form of hexagonal rods on increasing the annealing temperature to 300 degrees C. However, on further increasing the annealing time to 3h at 300 degrees C, distorted cubical microstructures were observed. The microstructures had a higher Sb/Bi ratio, implying that these structures were Sb rich. The thermoelectric properties of the nanostructured BixSb2-xTe3 films were studied as a function of annealing temperature and time. An enhancement of about two orders of magnitude is observed both in the S and power factor for the samples annealed at 300 degrees C for 3h. This enhancement is attributed to the energy filtering of charge carriers at the junction of the BixSb2-xTe3 matrix and Sb-rich inclusions. These results indicate that annealing is an efficient way of tuning the growth of microstructures and the S of BixSb2-xTe3 thin films.