Electronic structure of the Si(100) surface A defects analyzed by scanning tunneling spectroscopy at 80 K

The A defects on the Si(100) surface can be classified as A₁, A₂, and A₃ at low temperatures. We carried out scanning tunneling microscopy observations and scanning tunneling spectroscopy measurements at approximately 80 K to study their electronic structures. We found that the A₁ defect is semiconductive similar to the A defect at room temperature (RT), while the A₂ and A₃ defects exhibited states in the surface band gap at 80 K. On comparing these results with the theoretical models, we concluded that the A₁ defect correspond to the Rebonded vacancy model. The broken vacancy model and the twisted vacancy models are the possible candidates for the A₂ and A₃ defects, respectively.