Electronic Density Decay Lengths of Pb Films from First Principles Calculations

The electronic density decay lengths of freestanding Pb films are investigated by first-principles calculations. The results show that, like surface energy and work function, the electronic density decay length λ exhibits pronounced oscillatory behavior as a function of film thickness and this is expected to have an impact on surface chemical reactivity. For freestanding Pb(111) films, λ oscillates following a bilayer pattern interrupted by crossovers, and the separation between two neighbor crossovers is 9 monolayers. For the films on Si(111) substrates, the oscillations of the decay lengths are similar to those of freestanding films except for an extra phase shift.