Interplay between Structural and Thermoelectric Properties in Epitaxial Sb2+xTe3 Alloys

In recent years strain engineering is proposed in chalcogenide superlattices (SLs) to shape in particular the switching functionality for phase change memory applications. This is possible in Sb₂Te₃/GeTe heterostructures leveraging on the peculiar behavior of Sb₂Te₃, in between covalently bonded and weakly bonded materials. In the present study, the structural and thermoelectric (TE) properties of epitaxial Sb_2+xTe₃ films are shown, as they represent an intriguing option to expand the horizon of strain engineering in such SLs. Samples with composition between Sb₂Te₃ and Sb₄Te₃ are prepared by molecular beam epitaxy. A combination of X‐ray diffraction and Raman spectroscopy, together with dedicated simulations, allows unveiling the structural characteristics of the alloys. A consistent evaluation of the structural disorder characterizing the material is drawn as well as the presence of both Sb₂ and Sb₄ slabs is detected. A strong link exists among structural and TE properties, the latter having implications also in phase change SLs. A further improvement of the TE performances may be achieved by accurately engineering the intrinsic disorder. The possibility to tune the strain in designed Sb_2+xTe₃/GeTe SLs by controlling at the nanoscale the 2D character of the Sb_2+xTe₃ alloys is envisioned.