Tuning transport coefficients of monolayer MoSi<sub>2</sub>N<sub>4</sub> with biaxial strain*
Xiao-Shu Guo, San-Dong Guo
Abstract
Experimentally synthesized MoSi 2 N 4 ( Science 369 670 (2020)) is a piezoelectric semiconductor. Here, we systematically study the large biaxial (isotropic) strain effects (0.90–1.10) on electronic structures and transport coefficients of monolayer MoSi 2 N 4 by density functional theory (DFT). With a / a 0 from 0.90 to 1.10, the energy band gap firstly increases, and then decreases, which is due to transformation of conduction band minimum (CBM). Calculated results show that the MoSi 2 N 4 monolayer is mechanically stable in the considered strain range. It is found that the spin-orbital coupling (SOC) effects on Seebeck coefficient depend on the strain. In unstrained MoSi 2 N 4 , the SOC has neglected influence on Seebeck coefficient. However, the SOC can produce important influence on Seebeck coefficient, when the strain is applied, for example, 0.96 strain. The compressive strain can change relative position and numbers of conduction band extrema (CBE), and then the strength of conduction bands convergence can be enhanced, to the benefit of n-type ZT e . Only about 0.96 strain can effectively improve n-type ZT e . Our works imply that strain can effectively tune the electronic structures and transport coefficients of monolayer MoSi 2 N 4 , and can motivate farther experimental exploration.