Tigran Simonian1,Ahin Roy1,Zdenek Sofer2,Valeria Nicolosi1
Trinity College Dublin1,University of Chemistry and Technology Prague2
Tigran Simonian1,Ahin Roy1,Zdenek Sofer2,Valeria Nicolosi1
Trinity College Dublin1,University of Chemistry and Technology Prague2
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.<br/>In this work, the ternary chalcogenide TlGaSe<sub>2</sub> serves as a prototypical example of this type of analysis. TlGaSe<sub>2</sub> 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.<br/><br/>References:<br/>[1] A. Cengiz, Y. M. Chumakov, M. Erdem, Y. Sale, F. A. Mikailzade, and M. Y. Seyidov, “Origin of the optical absorption of TlGaSe<sub>2</sub> layered semiconductor in the visible range,” <i>Semicond. Sci. Technol.</i>, vol. 33, no. 7, 2018.<br/>[2] M. Caydasi, M. F. Mintas, Y. M. Chumakov, S. Volz, A. Cengiz, and M. Y. Seyidov, “A Study of Thermoelectric Performance of TlGaSe<sub>2</sub> Layered Dichalcogenides from First-Principles Calculations: Vacancy Defects Modeling and Engineering,” <i>Phys. status solidi</i>, vol. 259, no. 1, p. 2100409, Jan. 2022.<br/>[3] D. F. McMorrow, R. A. Cowley, P. D. Hatton, and J. Banys, “The structure of the paraelectric and incommensurate phases of TlGaSe<sub>2</sub>,” <i>J. Phys. Condens. Matter</i>, vol. 2, no. 16, pp. 3699–3712, 1990.