Flexible atomic buckling and homogeneous edge states in few-layer Bi(110) films

The structure and edge states of two-dimensional few-layer Bi(110) films grown on a graphene/SiC substrate were studied by low-temperature scanning tunneling microscopy and spectroscopy. We found that the local density of states of few-layer Bi(110) films are layer-dependent and that the films transition from exhibiting semiconducting characteristics to metallic ones as the number of layers increases. The in-plane lattice structure has numerous displacements and inversions, which implies that the atomic arrangement and atomic buckling in ultrathin Bi(110) films are flexible. The edges formed between 4-monolayer Bi(110) and graphene are reconstructed and distorted, and the corresponding edge states are topographically dependent. Steps from the substrate and domain boundaries also modify the electronic structures and induce additional defect-dependent states. We also found that the zigzag-shaped step edges in few-layer Bi(110) films are nonreconstructed and possess layer-dependent homogeneous edge states, providing a very likely platform for further research on quantum interference of the edge mode in order to confirm the topology in Bi(110).