Electronic Properties of Cs-Covered Surfaces of Graphite (0001)

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Abstract
The electronic properties of Cs-covered graphite surfaces were studied by low-energy electron diffraction, Auger-electron spectroscopy and work function measurements. The behaviors of an additional structure appearing with the adsorption of Cs on the high-energy side of the C KVV (272 eV) Auger spectra are interpreted in terms of the density of states (DOS) of the graphite π conduction band and the extra DOS induced by the alkali atom. The change in work functions is ascribed to a Fermi-level shift due to charge transfer from the Cs to the graphite π conduction band and the potential difference between the graphite surface and the Cs overlayer. Examination of the work function shows that the charge transfer per adsorbate is unity up to a relative coverage of θ=0.35 and thereafter decreases monotonically to a value of 0.35 at the full coverage θ=1.