Ultra thin Bismuth Selenide-Bismuth Telluride layers for thermoelectric applications

Publication date: Available online 14 December 2018Source: Materials Chemistry and PhysicsAuthor(s): A.M. Adam, A. El-Khouly, E. Lilov, Sh. Ebrahim, Y. Keshkh, M. Soliman, E.M. El Maghraby, V. Kovalyo, P. PetkovAbstractCrystalline thin films of Bi-Te-Se were deposited onto well cleaned glass substrates (BK7 type) by the vacuum thermal evaporation technique at a pressure of 10-3 Pa. Bulk samples were used as targets to evaporate the corresponding films. The internal microstructure of bulk samples and films were characterized by x-ray diffraction (XRD). Identifications of the microstructure and the surface morphology of the bulk and thin film samples were determined using scanning electron microscopy (SEM). Powder of the bulk alloys and the thin films of our products were observed to be polycrystalline in the form of hexagonal Bi2Se3 and Bi2Te3 structure. The material characteristic power factor of 74 μ W/ mK2 was observed as the maximum value of power factor obtained in our study, and that was for Bi2Te3 near room temperature. The dimensionless figure of merit (ZT) was estimated based on Seebeck coefficient and electrical conductivity measurements alongside with thermal conductivity estimations. ZT values of Bi2Se3 and Bi2Se1.5Te1.5 were significantly enhanced as temperature increased, whilst, ZT of Bi2Te3 exhibited an opposite behavior. A mechanical stress test was performed in order to investigate the suitability of our films for thermoelectric modulus.
Source: Materials Chemistry and Physics - Category: Materials Science Source Type: research