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Synthesis and thermal instability of high-quality Bi2Te3/Sb2Te3 superlattice thin film thermoelectrics

 
: Hansen, Anna-Lena; Dankwort, Torben; Winkler, Markus; Ditto, Jeffrey; Johnson, Dave C.; König, Jan D.; Bartholomé, Kilian; Kienle, Lorenz; Bensch, Wolfgang

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Chemistry of Materials 26 (2014), No.22, pp.6518-6522
ISSN: 0897-4756
ISSN: 1520-5002
English
Journal Article
Fraunhofer IPM ()
thermoelectrics; Ge-Si alloys; bismuth telluride; boundary scattering; solid-solutions; diffusion; phonons; Sb2Te3; merit; conductivity; devices

Abstract
The quality and temperature stability of 1 nm Bi2Te3/5 nm Sb2Te3 superlattices prepared by molecular beam epitaxy for the first time was investigated by in situ and ex situ X-ray diffraction and transmission electron microscopy. Upon heating, the superlattice structures are not stable against interdiffusion of the components, with micro- and nanostructural changes occurring at temperatures as low as 200 degrees C. The interdiffusion preferably starts next to superlattice defects. At 300 degrees C the Bi2Te3 and Sb2Te3 layers were mostly interdiffused, forming the thermodynamically stable Sb1.66Bi0.33Te3 alloy. The data suggests that structural integrity of Bi2Te3/Sb2Te3 superlattices will not be stable for extended times above 200 degrees C, thus inhibiting application of such superlattice s over a wide temperature range.

: http://publica.fraunhofer.de/documents/N-331960.html