Preparation of bismuth telluride thin films through interfacial reaction

Preparation of high-quality bismuth telluride films is essential for the realization of thermoelectric micro-coolers. In this study we have presented an approach to prepare bismuth telluride thin films with reasonable thermoelectric properties and very flat film morphology. Periodic Bi/Te multilayer structures were sputter-deposited at room temperature and transformed into bismuth telluride via Bi/Te interfacial reaction during post thermal annealing. Bi2Te3 was identified to be the major compound phase found in the annealed samples by X-ray diffraction analysis. The composition of the Bi/Te composite thin films has been modulated by adjusting the relative thicknesses of the Bi and Te layers in the multilayer structure. The sign of Seebeck coefficients reverses with increasing Te content from 46 to 70 at.%. The best thermoelectric power factors (= S2/ρ, S: Seebeck coefficient; ρ: resistivity) were measured to be 1.4 × 10− 3 and 0.6 × 10− 3 W/mK2 for the p-type and n-type composite films with 58 at.% Te and 67 at.% Te, respectively.