Chemisorption-induced multilayer relaxation changes: LEED study of Ni(110)-C(2×2)-S

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Abstract
The chemisorption of sulphur at the (110) face of nickel induces drastic changes in the multilayer relaxation: the oscillatory relaxation of the first and second interlayer distances at the clean surface (-8.4+or-0.8% and +3+or-1%, respectively) changes in sign and increases slightly (+10+or-2% and -3.5+or-1.5%) upon sulphur chemisorption. The sulphur atoms are in the hollow adsorption site at 0.84+or-0.03 AA above the top nickel layer. This position is in good agreement with previous results obtained from angular-resolved Auger emission of sulphur or from Rutherford backscattering (RBS) with medium-energy ions. The authors also agree with the sign reversal of the relaxation of the top layer reported from RBS experiments, but they find that it is larger (+10% instead of +6%) and discover, in addition, a substantial contraction of the second interlayer spacing.
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