An extended X-ray absorption fine structure study of Mn ultrathin films grown on Cu(1 0 0)

Ultrathin Mn films grown at room temperature on Cu(1 0 0) have been studied with extended X-ray absorption fine structure (EXAFS) assisted by low energy electron diffraction (LEED). At a film coverage Θ=0.5 monolayers (ML), corresponding to the presence of a c(2×2) superstructure in the LEED pattern, we obtained values of the bond length and of the effective coordination number which are consistent with the formation of a surface MnCu alloy, in agreement with previously published results. At increasing coverage the degradation of the LEED pattern with the disappearence of the spots at Θ=6 ML and the absence of a clear multishell signal in the EXAFS results point towards a progressive decrease of long-range crystal order, probably caused by the strain of Mn films growing in a strongly distorted lattice.