Weakly bound submonolayer adsorbates provide important insight into fundamental descriptions of physics that would otherwise be masked, or even suppressed, by strong effects such as chemical binding. We focus on two surface effects: transient mobility at the microscopic scale, and symmetry-breaking at the atomic one.

We present a novel island nucleation and growth model that explicitly includes, at the microscopic scale, the behavior of transient (ballistic) monomers. At a deposition rate F , monomers are assumed to be in a hot precursor state before thermalizing. In the limiting regimes of fast (diffusive) and slow (ballistic) thermalization, we recover the expected scaling of the island density, N : N ∝ F^α. We construct effective growth exponents, α eff , and activation energies to properly characterize the transitional regions between these limiting regimes. Through these constructs, we describe a rich and complex structure of metastable limiting regimes, asymptotic behavior and energetically driven transitions. Application to N (F, T ) ofrecent organic-molecule deposition experiments yields excellent fits.

We have also studied, at the atomic scale, an effective potential mechanism that breaks the intrinsic two-fold sublattice (hexagonal) symmetry of (honeycomb) graphene using DFT calculations (VASP ver 5.3.3). We choose the specific system of CF3Cl adsorbates on single layer graphene, to benefit from experimental results obtained locally. Using ab initio van der Waals density functionals, we discover a physisorbed phase with binding energies of about 280 meV. For low coverages, sublattice symmetry-breaking effects are responsible for gap openings of 4 meV; contrastingly, in large coverages, it is the formation of ordered overlayers that opens gaps nearly 5 times as large, of roughly 18 meV. We discover that in both cases, differentiation of graphene’s two sublattices induces symmetry-breaking by means of adsorbate interactions that favor large ordered regions, coverage itself is insignificant. For CF3Cl adsorbates on bilayer graphene, symmetry-breaking effects caused by the formation of graphene-like overlayers, and not sublattice differentiation, opened gaps of 25 meV, the largest in our study.