Surface Barrier States and Resonances of Metals
We discuss here our realistic plane-wave scattering method for calculating the band structure of image and Shockley surface barrier states and resonances above and below the vacuum level. This method can be applied to any metal surface and is just as accurate for resonances as slates. The approach is the only one to date which is sufficiently accurate to enable determination of the surface barrier shape from a detailed match of calculated and measured band structure.
We show the calculated band structure for a transition metal surface W(OOl)-lxl where a Rydberg series of strong image resonances is predicted and two image resonances a few eV above the vacuum level are found to be particularly sensitive to the image-plane position and saturation of the barrier.
The above-vacuum level band structure to 10.5 eV is then calculated and image resonance bands are found to exist up to this energy. We conclude that above-vacuum image and Shockley resonances are likely to exist up to 10.5 eV for W(OOl)-lxl surface and this is a region which has not been explored to any great extent by experiment.
We then calculate the reflectivity of the 00 beam in very low energy electron diffraction (VLEED) for energy ranges and angles of incidence corresponding to the same values of reduced parallel momentum of the electron as occurs in calculations of the above-vacuum level surface barrier resonance band structure. The connection between surface barrier fine-structure scattering features in VLEED and the abovevacuum level surface barrier resonance band structure is discussed.
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