Quantum modulation of island nucleation on top of a metal nanomesa

We present a theoretical analysis of selectivity of nucleation location for the two-dimensional island on top of a metal nanomesa. It has been observed experimentally that the nucleation can start either along the periphery of the mesa top or in the middle, depending on the mesa height. Such an intriguing nucleation behavior is shown to originate from the thickness-dependent mesa edge barrier for an adatom to jump off the mesa, which we attributed to be induced by the quantum size effect. Based on the experimentally observed nucleation locations, we estimate that the mesa edge barriers for the 5- and 6-layer Pb(1 1 1) mesas can differ by ∼19 ± 5 meV.