Electronic properties and STM images of doped bilayer graphene

Electronic structures and scanning tunneling microscopy (STM) patterns of boron-and nitrogen-doped bilayer graphene are predicted using state-of-the-art first-principles calculations. Asymmetric doping is considered, leading to different charge-carrier densities on each graphene layer and to a band-gap opening. When lying on the top layer, the local STM patterns of the dopant are predicted to be similar to images observed in monolayer graphene. In contrast, the local electronic states of the buried dopant are not directly detectable by STM. However, by analyzing the charge transfer between graphene layers and its effect on the contrast of the STM image, the chemical doping is found to affect the symmetry (hexagonal and triangular) of the observed lattice for both the top doped surface and the buried doped layer. Consequently, our ab initio simulations predict a possible indirect detection of N or B dopants buried in bilayer graphene when such a contrast is revealed by a series of STM images or using scanning tunneling spectroscopy.