Prediction of Two-Dimensional Group IV Nitrides AxNy (A = Sn, Ge, or Si): Diverse Stoichiometric Ratios, Ferromagnetism, and Auxetic Mechanical Property

In this work, we unveiled a new class of two-dimensional (2D) group IV nitride A(x)N(y) (A = Sn, Ge, or Si) prototypes, C2/m A(4)N, P (3) over bar m1 A(3)N, P3m (1) over bar A(2)N, P3 (3) over bar m1 A(3)N(2), P (6) over bar m2 AN, P (3) over bar m1 AN, P (6) over bar 2m A(3)N(4), P3m1 A(2)N(3), P (4) over bar 21m AN(2), and P (3) over bar m1 AN3, by using evolutionary algorithms combined with first-principles calculations. Using HSE06 functional calculations, a wide range of band gaps from metal to semiconductor (0.405-5.050 eV) and ultrahigh carrier mobilities (1-24 x 10(3) cm(2) V-1 s(-1)) were evidenced in these 2D structures. We found that 2D P3m1 Sn2N3, Ge2N3, and Si2N3 are intrinsic ferromagnetic semiconductors with gaps of 0.677, 1.285, and 2.321 eV, respectively. The lattice symmetry and Si-to-N2 charge transfer upon strain lead to large anisotropic negative Poisson's ratios (-0.281 to -0.146) along whole in-plane directions in 2D P4 (2) over bar 1m SiN2. Our findings not only enrich the family of 2D nitrides but also highlight the promising optoelectronic and nanoauxetic applications of 2D group IV nitrides.

Automated summary

In this work, a new class of two-dimensional IV group nitrides has been unveiled using evolutionary algorithms combined with first-principles calculations. These structures exhibit wide band gaps and high carrier mobilities, and some configurations display intrinsic ferromagnetic semiconductor properties. Additionally, a particular two-dimensional structure shows anisotropic negative Poisson's ratios upon strain.