| AVS 55th International Symposium & Exhibition | |
| Surface Science | Wednesday Sessions |
| Session SS2-WeA |
| Session: | Electrons and Electronic Spectra at Surfaces |
| Presenter: | R.G. Tobin, Tufts University |
| Authors: | C. Liu, Tufts University R.G. Tobin, Tufts University |
| Correspondent: | Click to Email |
Surface resistivity – the increase in the electrical resistivity of a thin metal film due to surface defects or impurities – is a simple and readily measured property that provides a window into complex nonequilibrium surface processes. It originates in the diffuse scattering of the metal’s conduction electrons by the localized potential created by the surface modification, and depends in complicated fashion on the local electronic structure of the scatterer. The variation of surface resistivity with coverage, for both single adsorbates and coadsorption systems, gives insight into the effects of surface defects and neighboring adsorbates on the electron-scattering probability. We report on several surface resistivity studies that reveal different aspects of adsorption. All are carried out on 50 nm thick epitaxial Cu(100) films grown on H-terminated Si(100) substrates. CO adsorption on these films exhibits striking differences in electron-scattering cross section for adsorption on different sites, with CO on defect sites exhibiting near-zero net scattering.1 Studies of oxygen and sulfur adsorption reveal the effects of interadsorbate interactions. Individually adsorbed oxygen and sulfur show very different coverage-dependences, with oxygen atoms acting as independent non-interacting scatterers while at high coverages sulfur strongly suppresses scattering by nearby sulfur atoms.2 Sulfur has a similar effect on coadsorbed oxygen, reducing its effective scattering cross-section essentially to zero when the two atoms are adsorbed on adjacent lattice sites.3 We suspect that the apparently zero differential resistivity observed for defect-bonded CO and for adsorption of O or S near a pre-adsorbed sulfur atom results not from zero electron scattering by the added adsorbate but from cancellation of the new adsorbate’s added scattering by a reduction in scattering from the defect site or preadsorbed sulfur. These results can be analyzed qualitatively in terms of the behavior of adsorbate-derived orbitals near the Fermi level.
1 C. Liu and R.G. Tobin, J. Chem. Phys. 126, 129705 (2007).
2 R.G. Tobin, Surf. Sci. 524, 183 (2003).
3 C. Liu and R.G. Tobin, J. Chem. Phys., in press.