Novel Two-Dimensional Layered MoSi 2 Z 4 (Z = P, As): New Promising Optoelectronic Materials.

Very recently, two new two-dimensional (2D) layered semi-conducting materials MoSi 2 N 4 and WSi 2 N 4 were successfully synthesized in experiments, and a large family of these two 2D materials, namely MA 2 Z 4 , was also predicted theoretically (Science, 369, 670 (2020)). Motivated by this exciting family, in this work, we systematically investigate the mechanical, electronic and optical properties of monolayer and bilayer MoSi 2 P 4 and MoSi 2 As 4 by using the first-principles calculation method. Numerical results indicate that both monolayer and bilayer MoSi 2 Z 4 (Z = P, As) present good structural stability, isotropic mechanical parameters, moderate bandgap, favorable carrier mobilities, remarkable optical absorption, superior photon responsivity and external quantum efficiency. Especially, due to the wave-functions of band edges dominated by d orbital of the middle-layer Mo atoms are screened effectively, the bandgap and optical absorption hardly depend on the number of layers, providing an added convenience in the experimental fabrication of few-layer MoSi 2 Z 4 -based electronic and optoelectronic devices. We also build a monolayer MoSi 2 Z 4 -based 2D optoelectronic device, and quantitatively evaluate the photocurrent as a function of energy and polarization angle of the incident light. Our investigation verifies the excellent performance of a few-layer MoSi 2 Z 4 and expands their potential application in nanoscale electronic and optoelectronic devices. [ABSTRACT FROM AUTHOR]