Growth of thermoelectric Bi85Sb15 alloy thin films and their characterization by XRD,TEM & RBS

R. C. Mallik1, S. Rath2, V. Damodara Das1

1Thin Film Laboratory, Department of Physics, Indian Institute of Technology, Madras, Chennai 600 036, India

2Institute of Physics, Bhubaneswar-751005, Orissa, India

Bismuth and antimony are semimetals. The Bi(1-x)Sbx alloys are found to show fair seebeck coefficient (0.04<x<0.22) suitable for thermoelectric application. Bulk Bi85Sb15 was prepared by the melt-quenching technique. The constituent materials bismuth and antimony were taken in the desired stoichiometric ratio in a quartz ampoule sealed at a pressure of 10-5 mbar. According to the phase diagram, the temperature was set. When the alloy was formed at 7500 C the sample was quenched in liquid nitrogen. The phase formation was confirmed by XRD. The thin films were prepared by the conventional flash evaporation technique to ensure the stoichiometry avoiding dissociation.

The XRD and Transmission Electron Microscopy (TEM) studies were done for structural characterization of thin films. Compositional analysis was done by Rutherford Back Scattering(RBS). The results show that our method of preparation of bulk as well as thin films are maintaining stoichiometry .The thickness of thin films were measured by in-situ quartz crystal monitor and evaluated from RBS spectra. The thermoelectric power was measured by the integral method. The detection of nature of scattering will help us to optimize the figure of merit and hence to enhance the thermoelectric properties. The scattering occurs due to several factors, i.e., it may due to the various defects or impurity atoms or the lattice. We are interested to know the nature of scattering present in our sample.