Electronic structure and switching behavior of the metastable silicene domain boundary

Silicene, a silicon allotrope with a buckled honeycomb lattice, has been extensively studied in the search for materials with graphene-like properties. Here, we study the domain boundaries of a silicene 4 x 4 superstructure on an Ag(111) surface at the atomic resolution using scanning tunneling microscopy (STM) and spectroscopy (STS) along with density functional theory calculations. The silicene domain boundaries (beta-phases) are formed at the interface between misaligned domains (alpha-phases) and show a bias dependence, forming protrusions or depressions as the sample bias changes. In particular, the STM topographs of the silicene-substrate system at a bias of similar to 2.0V show brightly protruding domain boundaries, which can be explained by an energy state originating from the Si 3s and 3p(z) orbitals. In addition, the topographs depicting the vicinity of the domain boundaries show that the structure does not follow the buckled geometry of the atomic ball-andstick model. Inside the domain, STS data showed a step-up at similar to 0.4 V, which originated from the Si 3p orbitals. We found this step-up to have shifted, which may be attributed to the strain effect at the interface regions between silver and silicene and between the domain and its boundary upon performing spatially resolved STS measurements. The metastable characteristic of the domain boundary (beta-phase) causes changes, such as creation or annihilation, in the buckling structures (switching behavior). The observed low activation energy for the buckling change between distinct states may find applications in the electronic control of properties related to domain boundary structures in silicene. Published by AIP Publishing.