STM Study of CO and NO on Pt(001)

Adsorption of CO and NO Moleculcs on a Pt(OO1)-hex R0.7° surface at 90 K is investigated by scanning tunneling microscopy (STM) in ultra-high vacuum environments. At an initial stage of adsorption, both molecules are preferentially adsorbed on th e Iess 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 Iower migration energy in this direction. The extra Pt atoms produced from adsorbate-induced restructuring give rise to anisotropic islands on the ( 1 x 1 ) surface. Each of the adsorbed NO molecules at low coveragcs is atomicalIy resolved during STM observation. However, the spots of the adsorbed CO are invisible.Such a behavior is probably explained in terms of different interactions between the adsorbates.