Ab initio study of energy-band modulation in graphene-based two-dimensional layered superlattices

Periodically stacked graphene and its insulating isomorph provide a fascinating structural element in implementing highly functional superlattices at the atomic scale, which offers possibilities in designing nanoelectronic and photonic devices. Using density functional theory (DFT) calculations, we demonstrate that various types of superlattices can be obtained by stacking two-dimensional (2D) materials alternately, namely, graphene, hexagonal boron nitride (h-BN), hydrogenated graphene, and fluorinated graphene. The energy band in layer-stacked superlattices is found to be more sensitive to the barrier width than that in conventional III-V semiconductor superlattices. When adding more than one atomic layer to the barrier in each period, the coupling of electronic wavefunctions in neighboring potential wells can be significantly reduced, which leads to the degeneration of continuous subbands into quantized energy levels. When varying the well width, the energy levels in the potential wells along the L-M direction behave distinctly from those along the K-H direction. Our results indicate that the quantized energy states in atomic-layered superlattices can be effectively tuned by modifying each individual barrier/well layer; enabling atomic-scale material engineering.