Angle resolved ion-electron spectroscopy (ARIES), a new technique to study surface structural features

Angle Resolved Ion-Electron Spectroscopy (ARIES), combined with Low Energy Ion Scattering (LEIS), is presented as a new technique with a wide applicability to study solid surfaces. Energy and angular distribution of secondary electrons emitted due to the ionization of (ad)-sorbates on a Cu(001) surface upon bombardment with 10 keV He+ are examined. When sulphur atoms - diffused from the bulk to the surface upon a 6000C anneal - are involved in the emission process, a strongly anisotropical emission is found. The anisotropy is related only to the incoming beam direction and appears to be fully independent of the copper target orientation. Some points of importance for a theoretical description are discussed. The anisotropy effect can effectively be used to determine the relative position of contaminant and substrate atoms in the uppermost surface layers. Thus, it is found that (1) sulphur atoms diffused to positions just below the surface occupy substitutional sites and (2) in this situation surface relaxation for the copper atoms in the first layer is negligible. (author)