Local tunneling barrier height studies of thermally treated CO-and O-covered Pt(100) surfaces

CO- and O-covered Pt(100) surfaces after thermal treatment have been studied by scanning tunneling microscopy (STM) and local tunneling barrier height (LBH) imaging. The coexistence of the reconstructed (hex) and reconstruction-deconstructed (1 × 1) domains with similar well-defined shapes is observed for both surfaces. However, the LBH images show that the local work function of the (1 × 1) domains is lower than that of the hex domains in the case of the CO-covered surface, but higher in the case of the O-covered surface. This feature is considered due to the electric dipole moment induced by O₂ adsorption being higher than that induced by CO adsorption.