STM study of CO and NO on Pt(001)

Adsorption of CO and NO molecules on a Pt(001)-hex R0.7 degrees surface at 90 K is investigated by scanning tunneling microscopy (STM) in ultra-high v acuum environments. At an initial stage of adsorption, both molecules are p referentially adsorbed on the less coordinated Pt atoms of the surface with hexagonal structure, which act as active sites. Domains of the adsorbates grow parallel to the stripe structure of the reconstructed surface because of lower migration energy in this direction. The extra Pt atoms produced fr om adsorbate-induced restructuring give rise to anisotropic islands on the (1 x 1) surface. Each of the adsorbed NO molecules at low coverages is atom ically resolved during STM observation. However, the spots of the adsorbed CO are invisible. Such a behavior is probably explained in terms of differe nt interactions between the adsorbates.