Thermoelectric and optical properties of 2D hexagonal Dirac material Be3X2(X = C, Si, Ge, Sn): A density functional theory study

Abstract

The thermoelectric and optical properties of the 2D hexagonal Dirac material B e 3 X 2 (X = C, Si, Ge, Sn) have been investigated by the first-principles method. These structures have thermoelectric properties superior to graphene. The pristine B e 3 C 2, B e 3 S i 2, B e 3 G e 2 structures show an extraordinary large Seebeck coefficient, power factor, and Z T ∼ 1 at a low temperature. The maximum thermoelectric efficiency is observed at T ∼ 100-400 K and chemical potential in the range of -0.2 to 0.2 eV. The system performs better when they are n-doped. The optical properties indicate a contribution from both interband and intraband transitions. At a low frequency, the system shows optically metallic and semiconducting characteristics for parallel and perpendicular polarization of incident light, respectively. The materials behave as optically transparent for visible light. A σ - σ ∗ - interband transition is observed in the UV region of the electromagnetic spectrum. Both π and π + σ plasmon peaks are identified in the infrared and UV regions, respectively. All these intriguing properties of the B e 3 X 2 monolayer may motivate fabricating this material and its application in smart thermoelectric and opto-electronic devices.