Metal-free spin and spin-gapless semiconducting heterobilayers: monolayer boron carbonitrides on hexagonal boron...

The interfaces between monolayer boron carbonitrides and hexagonal boron nitride (h-BN) play an important role in their practical applications. Herein, we respectively investigate the structural and electronic properties of two metal-free heterobilayers constructed by vertically stacking two-dimensional (2D) spintronic materials (B₄CN₃ and B₃CN₄) on a h-BN monolayer from the viewpoints of lattice match and lattice mismatch models using density functional calculations. It is found that both B₄CN₃ and B₃CN₄ monolayers can be stably adsorbed on the h-BN monolayer due to the van der Waals interactions. Intriguingly, we demonstrate that the bipolar magnetic semiconductor (BMS) behavior of the B₄CN₃ layer and the spin gapless semiconductor (SGS) property of the B₃CN₄ layer can be well preserved in the B₄CN₃/BN and B₃CN₄/BN heterobilayers, respectively. The magnetic moments and spintronic properties of the two systems originate mainly from the 2p_z electrons of the carbon atoms in the B₄CN₃ and B₃CN₄ layers. Furthermore, the BMS behavior of the B₄CN₃/BN bilayer is very robust while the electronic property of the B₃CN₄/BN bilayer is sensitive to interlayer couplings. These theoretical results are helpful both in understanding the interlayer coupling between B₄CN₃ or B₃CN₄ and h-BN monolayers and in providing a possibility of fabricating 2D composite B₄CN₃/BN and B₃CN₄/BN metal-free spintronic materials theoretically.