Evidence for an inhomogeneous–homogeneous transition in the surface local electrostatic potential of K-covered Al(100)

Resonant neutralization probabilities for 2 keV ⁷Li⁺ singly scattered from Al and K surface atomic sites are measured from K-covered Al(100). At low K coverages (0.03 ML), nearly all of the Li⁺ ions scattered from K are neutralized, while neutral fractions ranging from 32 to 65 % are measured for scattering from Al. This indicates that the surface local electrostatic potential is laterally inhomogeneous. At higher K coverages, on the other hand, the neutral fractions for scattering from Al and K become nearly equal, showing that the inhomogeneities are greatly reduced. This represents direct experimental evidence of such a transition.