Ballistic Electron Emission Microscopy on CoSi${}_2$/Si(111) interfaces:   band structure induced atomic-scale resolution and role of localized surface   states
  Applying a Keldysh Green`s function method it is shown that hot electrons injected from a STM-tip into a CoSi${}_2$/Si(111) system form a highly focused beam due to the silicide band structure. This explains the atomic resolution obtained in recent Ballistic Electron Emission Microscopy (BEEM) experiments. Localized surface states in the $(2 \times 1)$-reconstruction are found to be responsible for the also reported anticorrugation of the BEEM current. These results clearly demonstrate the importance of bulk and surface band structure effects for a detailed understanding of BEEM data. 
K. Reuter, F.J. Garcia-Vidal, P.L. de Andres, F. Flores, K. Heinz