Interplay between Structural and Thermoelectric Properties in Epitaxial Sb_2+xTe₃ Alloys

Abstract

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 Sb 2 Te 3 /GeTe heterostructures leveraging on the peculiar behavior of Sb 2 Te 3 , in between covalently bonded and weakly bonded materials. In the present study, the structural and thermoelectric (TE) properties of epitaxial Sb 2+x Te 3 films are shown, as they represent an intriguing option to expand the horizon of strain engineering in such SLs. Samples with composition between Sb 2 Te 3 and Sb 4 Te 3 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 Sb 2 and Sb 4 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+x Te 3 /GeTe SLs by controlling at the nanoscale the 2D character of the Sb 2+x Te 3 alloys is envisioned.

Towards Antimonene and 2D Antimony Telluride through Electrochemical Exfoliation

“…Compared to Sb 2 Te 3 , with higher interlayer distances and weaker interactions, there are not many exfoliation works reported too. High‐quality sheets of Sb and Sb 2 Te 3 have been obtained by epitaxial growth, mechanical and/or liquid‐phase exfoliation methods.…”

Phonon anharmonicities and ultrafast dynamics in epitaxial Sb2Te3

“…Electronic and lattice dynamics in chalcogenide-based materials are important factors in the performance of opto-electrical data-storage media and thermoelectric devices. Among these materials, Sb 2 Te 3 is a prototype as it is, together with GeTe and BiTe, one of the constituents of chalcogenide superlattices (CSLs) 1 , 2 . Combining Sb 2 Te 3 with one of the above-mentioned crystals together in one lattice, creates a superlattice with intriguing properties different or greater than those of its individual components.…”

“…Combining Sb 2 Te 3 with one of the above-mentioned crystals together in one lattice, creates a superlattice with intriguing properties different or greater than those of its individual components. In a recent study it has been demonstrated that a strong link exists among structural and thermoelectric properties in epitaxial Sb 2+ x Te 3 , the latter having implications also in phase change SLs upon strain engineering in designed Sb 2+ x Te 3 /GeTe multilayers 1 . Improved thermoelectric properties by nanostructuring Sb 2 Te 3 /BiTe multilayer have already been demonstrated 3 .…”

“…Sb 2 Te 3 is a narrow-band-gap semiconductor (E g = 0.26 eV around room temperature) with R -3 m space group and is composed of repeated planes of five-atomic layer lamellas separated by a van der Waals gap 11 . It exhibits a rather large concentration of p-type carriers around 10 20 cm −3 1 due to the presence of native antisite defects–Sb atoms occupying Te lattice sites–and is diamagnetic.…”

Crystallization Study of Ge‐Rich (GeTe)m(Sb2Te3)n Using Two‐Step Annealing Process

“…Between each annealing step, the samples were investigated by means of X‐ray diffraction (XRD) and Raman spectroscopy. In the recent years Raman spectroscopy was extensively exploited by our group to investigate GST, Sb 2 Te 3 /GeTe and Sb 2 Te 3 /GST SLs, and most recently Sb 2+x Te 3 alloys . Different annealing conditions are tested, allowing to identify T x and to optimize a recipe to reduce the segregation.…”