A systematic study was made of the structures of mono bilayer atomic steps, on the 7 x 7 reconstructed (111) surface, whose edges were parallel to the unit-cell boundary. Atomic steps in all possible 14 step groups were observed; thus giving a complete picture of the step structure. The upper step edges of 10 groups terminated at unit-cell boundaries, while the remaining 4 groups did not. The step structure which formed was the result of 2 factors which competed in minimizing the surface free energy: these were the structural integrity of the upper step edge, and the width of the transition region at the lower terrace. There was evidence that step formation was affected by the annealing method that was used.

Y.Wang, T.T.Tsong: Physical Review B, 1996, 53[11], 6915-8