It was noted that the A-defects on the (100) surface at low temperatures could be classified into A1, A2 and A3. Scanning tunnelling microscopy and scanning tunnelling spectroscopy were used, at 80K, to study their electronic structures. The A1 defect was semiconductive; rather like the A defect at room temperature. Meanwhile, the A2 and A3 defects exhibited states in the surface band-gap at 80K. Upon comparing these results with theoretical models, it was concluded that the A1 defect corresponded to the rebonded vacancy model. It was suggested that the broken vacancy model and the twisted vacancy model were possible candidates for the A2 and A3 defect, respectively.

Electronic Structure of the Si(100) Surface A Defects Analyzed by Scanning Tunnelling Spectroscopy at 80K Y.Sainoo, T.Kimura, R.Morita, M.Yamashita, K.Hata, H.Shigekawa: Japanese Journal of Applied Physics - 1, 1999, 38[6B], 3833-6