LEED STUDY OF STEPPED CO(11(2)OVER-BAR-0) PREPARED BY ION-BOMBARDMENT

The effect of ion bombardment with Ar+ and Kr+ on Co(<11(2)over bar 0> ) has been studied by means of low energy electron diffraction (LEED), X-ray photoelectron spectroscopy (XPS) and UV photoelectron spectrosc opy (UPS). At 300 K, the ion bombardment leads to the formation of a r egularly stepped surface, as determined by the diffraction pattern. A geometrical evaluation of this pattern allowed development of a model of the stepped surface. The step width is found to vary between 1.4 +/ - 0.5 nm and 2.8 +/- 0.5 nm corresponding to 3-5 or 6-8 unit cells, re spectively. The step depth of 0.12 +/- 0.02 nm is identical to the ato mic distance between two consecutive layers of the Co(<11(2)over bar 0 >) surface. The orientation of the edges is preferentially parallel to the [<1(1)over bar 00>] direction. As formation of these steps due to stabiIisation by implanted noble gas atoms can be excluded, an altern ative explanation is discussed, which combines anisotropic properties of the surface and kinetic effects, similar to the layer restricted di ffusion (LRD) model.