ADSORPTION OF ATOMIC-HYDROGEN ON CU(001) STUDIED WITH HELIUM-ATOM SCATTERING

The adsorption and structures formed when atomic hydrogen is adsorbed on Cu(001) at 170 K have been investigated using helium-atom scatterin g. At low coverages a (2x1) structure forms with split half-order diff raction spots. The splitting indicates a small domain length, with ant iphase regions separated by boundaries having a c(2X2) atom arrangemen t. The surface corrugation obtained by diffraction intensity analysis is consistent with a single fourfold adsorption site. At higher covera ges an intermediate structure forms, which is characterized by predomi nantly (1X1) diffraction peaks, from which the saturation phase develo ps. Diffraction peaks corresponding to a (2 root 2x2 root 2)R45 degree s structure were observed at saturation, with additional broad peaks i ndicating domain boundaries where lattice strain in the reconstructed substrate may be relieved. The data indicate the domain boundaries hav e a width of 4a(0)-6a(0).