Thermoelectric Structure-Property Relationship Establishment in TlGaSe₂

Session

EMAG - Functional Materials

Authors

Tigran Simonian (1, 3), Dr. Ahin Roy (1, 3), Prof. Zdenek Sofer (2), Prof. Valeria Nicolosi (1, 3)

Affiliations

1. Advanced Microscopy Lab, Trinity College Dublin
2. Department of Inorganic Chemistry, University of Chemistry and Technology
3. School of Chemistry, Trinity College Dublin

Keywords

thermoelectric, STEM, DFT, ternary chalcogenide, phonon dispersion, stacking faults, planar defects, 2D materials, low dimensional materials

Abstract text

Layered 2D materials are increasingly investigated for their often highly anisotropic properties, such as thermoelectricity. Such a property is useful in electronics, such as transistors and sensors, where wasted heat is not only economically and environmentally unsustainable, but can also be detrimental to device performance. It is repeatedly assumed that planar defects, such as stacking faults, affect the thermoelectric properties of these materials [1-2]. However, to date, no comprehensive study into establishing this relationship has been performed.

In this work, the ternary chalcogenide TlGaSe₂ serves as a prototypical example of this type of analysis. TlGaSe₂ is characterised via (scanning) transmission electron microscopy (STEM) and density functional theory (DFT) simulations. Streaking in selected area diffraction patterns are correlated to simulations which indicate the presence of stacking faults in the growth direction [3]. High resolution STEM confirms these stacking faults and indicates a lack of long-range order to the stacking. DFT calculations reveals a high preference for the system to include these faults. This is then coupled with phonon dispersion and electron transmission simulations to confirm their relationship to the thermoelectric properties of the material.

References

[1] A. Cengiz, Y. M. Chumakov, M. Erdem, Y. Şale, F. A. Mikailzade, and M. Y. Seyidov, “Origin of the optical absorption of TlGaSe₂ layered semiconductor in the visible range,” Semicond. Sci. Technol., vol. 33, no. 7, 2018.

[2] M. Çaydaşı, M. F. Mintaş, Y. M. Chumakov, S. Volz, A. Cengiz, and M. Y. Seyidov, “A Study of Thermoelectric Performance of TlGaSe₂ Layered Dichalcogenides from First‐Principles Calculations: Vacancy Defects Modeling and Engineering,” Phys. status solidi, vol. 259, no. 1, p. 2100409, Jan. 2022.

[3] D. F. McMorrow, R. A. Cowley, P. D. Hatton, and J. Banys, “The structure of the paraelectric and incommensurate phases of TlGaSe₂,” J. Phys. Condens. Matter, vol. 2, no. 16, pp. 3699–3712, 1990.