New group V-graphyne: 2D direct semiconductors with remarkable carrier mobilities, thermoelectric performance and thermal stability

Abstract Past decades have witnessed the great progress and successes in the research and applications of two-dimensional (2D) carbon materials like graphene, graphdiyne and etc. Similar to pure 2D carbon materials, 2D carbon nitrides like h-BN also possess excellent electronic, mechanical and optical properties. In this work, stimulated by the chemical tuition of atomic substitution, a new family of monolayer group V-graphyne (C16N4, C16P4, C16As4) with rhombic lattice is designed by replacing some C atoms with group-V elements of N, P or As in 2D graphyne. By using first-principles approach, we investigate their thermal stability, electronic/thermal transport properties, and thermoelectric performance, and find that N(P,As)-graphyne monolayers are semiconductors with considerable direct band-gap values of 0.87 eV (0.59 eV, 0.71 eV) respectively. Ab initio molecular dynamics results demonstrate that N(P,As)-graphyne monolayers maintain stable up to 1500 K . They all possess high carrier mobilities with the order of 10 5 cm 2 V − 1 s − 1 for electron along zigzag direction. Under the uniaxial tensile strains in the range of 0 % to 10 % , N(P,As)-graphyne monolayers keep direct-bandgap properties and the effective mass of carriers can be effciently tuned. Morever, the calculated thermoelectric figure of merits at room temperature for the new monolayer group V-graphyne are 0.62 ∼ 0.69 due to the low lattice thermal conductivity, which are comparable to some conventional thermoelectric materials. Their excellent electronic transport and thermoelectric performance make N(P,As)-graphyne monolayers promising in high-speed (opto)electronic and thermoelectric devices, and the strain-engineering properties may lead to applications in flexible nanoelectronics.