Magnetic semiconducting borophenes and their derivatives.

Two semiconducting borophenes with layer-dependent magnetism are predicted based on spin-polarized density functional theory. Both monolayer borophenes are ferromagnetic. One is composed of B 3 and B 15 triangular motifs, exhibiting bipolar spin polarization and a magnetic moment of 1.00 μ B per primitive cell. The other consists of B 15 triangular motifs, possessing a Curie temperature of about 437 K and a magnetic moment of 3.00 μ B per primitive cell. B atoms located between the triangular motifs are essential for inducing ferromagnetism in monolayer borophenes. However, bilayer borophenes with high-symmetry stacking orders are nonmagnetic. Furthermore, magnetic boron nanotubes and fullerenes could be made of monolayer borophenes. Finally, we propose to fabricate these magnetic semiconducting borophenes from the buckled triangular structure of borophenes via selective electron beam ionization of B atoms by scanning transmission electron microscopy.