Synthesis and Thermal Instability of High-Quality Bi2Te3/Sb2Te3 Superlattice Thin Film Thermoelectrics

• Published in: Chemistry of materials 2014-11, Vol.26 (22), p.6518-6522
• Main Authors: Hansen, Anna-Lena, Dankwort, Torben, Winkler, Markus, Ditto, Jeffrey, Johnson, Dave C, Koenig, Jan D, Bartholomé, Kilian, Kienle, Lorenz, Bensch, Wolfgang
• Format: Article
• Language: English
• ISSN: 0897-4756; 1520-5002
• DOI: 10.1021/cm5031574

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 °C. The interdiffusion preferably starts next to superlattice defects. At 300 °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 °C, thus inhibiting application of such superlattices over a wide temperature range.