Ballistic thermoelectric properties of monolayer semiconducting transition metal dichalcogenides and oxides

• Published in: Physical review. B 2019-08, Vol.100 (8), p.1, Article 085415
• Main Authors: Özbal, G., Senger, R. T., Sevik, C., Sevinçli, H.
• Format: Article
• Language: English
• Subjects: Chalcogenides; Chromium; Figure of merit; First principles; Hafnium compounds; Molybdenum; Phases; Thermal conductivity; Thermoelectricity; Titanium; Transition metal compounds; Transport properties; Tungsten; Zirconium oxides
• ISSN: 2469-9950; 2469-9969
• DOI: 10.1103/PhysRevB.100.085415

Combining first-principles calculations with Landauer-Büttiker formalism, ballistic thermoelectric transport properties of semiconducting two-dimensional transition metal dichalcogenides (TMDs) and oxides (TMOs) (namely MX2 with M = Cr, Mo, W, Ti, Zr, Hf; X = O, S, Se, Te) are investigated in their 2H and 1T phases. Having computed structural, as well as ballistic electronic and phononic transport properties for all structures, we report the thermoelectric properties of the semiconducting ones. We find that 2H phases of four of the studied structures have very promising thermoelectric properties, unlike their 1T phases. The maximum room temperature p-type thermoelectric figure of merit (ZT) of 1.57 is obtained for 2H−HfSe2, which can be as high as 3.30 at T=800 K. Additionally, 2H−ZrSe2, 2H−ZrTe2, and 2H−HfS2 have considerable ZT values (both n- and p-type), that are above 1 at room temperature. The 1T phases of Zr and Hf-based oxides possess relatively high power factors, however their high lattice thermal conductance values limit their ZT values to below 1 at room temperature.