Two-dimensional quantum confinement effects on thermoelectric properties of MgO monolayers: A first principle study

Abstract

In this paper, the thermoelectric properties of magnesium oxide in the bulk and monolayer (ML) phases in the two facets of (100) and (111) have been calculated and compared by using density functional theory (DFT) and Boltzmann theory. The electronic band structure calculations of bulk and monolayers of MgO indicate that the band gap for bulk and MgO(100) ML is direct, and indirect for MgO(111) ML Κ-to Γ-point. The estimated band gaps are in good agreement with other theoretical and experimental works. Due to the quantum confinement effects, two small peaks are observed in the n-doping region of the room temperature Seebeck coefficients of the monolayers which are not present in the bulk structure. In addition, we demonstrate that the room temperature figure of merit of MgO(100) ML has a remarkable peak at μ ​= ​2.71 ​eV with the value of about 1.5 which is attributed to its corresponding Seebeck coefficient peak. Beside, with increasing temperature, this peak shifts to the lower chemical potentials and reaches to 1.8 ​at ​T ​= ​800 ​K and μ ​= ​2.4 ​eV. Our findings show that a proper n-doping MgO(100) ML is a promising material for future thermoelectric applications at room and even high temperatures.