Berlin 2018 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 48: Thermoelectricity

HL 48.1: Talk

Thursday, March 15, 2018, 17:00–17:15, EW 015

Ab-initio calculations of the thermoelectric properties of
MXenes — •Udo Schwingenschlögl, Appala Naidu Gandi, and Sonu Kumar — King Abdullah University of Science and Technology (KAUST), Physical Science and Engineering Division (PSE), Thuwal 23955-6900, Saudi Arabia

Ab-initio calculations are used to study the MXenes Ti₂CO₂, Zr₂CO₂, and Hf₂CO₂ in order to evaluate the role of the metal atom for the thermoelectric properties. The lattice thermal conductivity is demonstrated to grow along the series Ti-Zr-Hf in the temperature range 300-700 K, resulting in the highest figure of merit in the case of Ti₂CO₂. Flat conduction bands promote the thermopower in the case of n-doping. Functionalization effects are studied for Sc₂C, which is semiconducting for various functional groups, including O, F, and OH. The lowest lattice thermal conductivity is found for OH functionalization. Despite a relatively low thermopower, Sc₂C(OH)₂ therefore and due to a high electrical conductivity can be interesting for intermediate-temperature thermoelectric applications. We also discuss results on heterostructures built of MXenes and transition metal dichalcogenide monolayers. Low frequency optical phonons are found to occur as a consequence of the van der Waals bonding. They contribute significantly to the thermal transport and compensate for reduced contributions of the acoustic phonons (strong scattering in heterostructures), such that the thermal conductivities become similar to those of the constituent MXenes. References: Chem. Mater. 28, 1647 (2016); Phys. Rev. B 94, 035405 (2016); J. Phys.: Condens. Matter 29, 035504 (2017).