THE STUDY OF MGO(001) SURFACES BY PHOTOELECTRON DIFFRACTION

The X-ray photoelectron diffraction (XPD) technique has been used to s tudy MgO(001) surfaces. In the angular distribution profiles from MgO, the forward scattering peaks do not always correspond to the low inde x crystallographic directions. This is unexpected but is also observed in the results of the multiple scattering calculations. We also obser ve differences between the XPD from magnesium and oxygen lines. This i s apparent from the large angular shifts between the forward scatterin g peaks in the diffraction pattern from the two emitters, which occupy crystallographically equivalent sites. Although these peak shifts are in qualitative agreement with a model based on a rumpled MgO surface, multiple scattering calculations rule out this explanation of the ano malies.