An extended X-Ray Absorption Fine Structure study of Mn ultrathin films grown on Cu(100)

Ultrathin Mn ®lms grown at room temperature on Cu(1 0 0) have been studied with extended X-ray absorption ®nestructure (EXAFS) assisted by low energy electron diraction (LEED). At a ®lm coverage H 0:5 monolayers (ML),corresponding to the presence of a c2 2 superstructure in the LEED pattern, we obtained values of the bond lengthand of the eective coordination number which are consistent with the formation of a surface MnCu alloy, in agreementwith previously published results. At increasing coverage the degradation of the LEED pattern with the disappearenceof the spots at H 6 ML and the absence of a clear multishell signal in the EXAFS results point towards a progressivedecrease of long-range crystal order, probably caused by the strain of Mn ®lms growing in a strongly distorted lattice.