Particle-resolved dynamics during multilayer growth ofC60

Abstract

Using large-scale kinetic Monte-Carlo (KMC) simulations, we investigate the non-equilibrium surface growth of the fullerene C60. Recently, we have presented a self-consistent set of energy barriers that describes the nucleation and multilayer growth of C60 for different temperatures and adsorption rates in quantitative agreement with experiments [Bommel et al., Nat. Comm. 5, 5388 (2014)]. We found that C60 displays lateral diffusion resembling colloidal systems, however it has to overcome an atom-like energetic step-edge barrier for interlayer diffusion. Here, we focus on the particle-resolved dynamics, and the interplay between surface morphology and particle dynamics during growth. Comparing C60 growth with an atom-like system, we find significant differences in the evolution of the surface morphology, as well as the single-particle dynamics on the growing material landscape. By correlating the mean-squared-displacement of particles with their current neighborhood, we can identify the influence of the different time scales that compete during growth and can pinpoint the differences between the two systems.

Limits of size scalability of diffusion and growth: Atoms versus molecules versus colloids

“…Regarding the energy parameters, we set E free = 0.54 eV in accordance with our previous studies for C60 [18,22]. We use this value for all three systems to obtain some degree of comparability (this corresponds to scaling F suitably).…”

“…1(a), a precise quantification of E n , even though it obviously depends on the material system. Following previous studies we set E C60 n = 0.13 eV [18] and E atom n = 0.72 eV [22]. For typical colloids, the pair interactions are tunable by changing solvent parameters, thus, there is not one unique choice for E colloid n .…”

“…In this regard, the best studied case, both experimentally (see, e.g., [12,13]) and theoretically [1,2,[14][15][16], is that of atomic homoepitaxy. Inspired also by the strong current interest in organic and hybrid thin films, recent studies of growth focus more on molecular systems [4,[17][18][19][20][21][22] and colloids [10,23] characterized by much larger length (nanometer to micrometer) and time scales. These developments raise intriguing questions: Can the detailed results established for atomic homoepitaxy be translated to molecular and colloidal systems?…”

“…These fundamental differences concerning step-edge diffusion are expected to strongly influence the growth behavior. To explore these effects quantitatively, we now consider hopping rates determining the dynamics of the systems in the framework of a (lattice-based) KMC approach [18,22,33,34]. For atomic and molecular systems (consisting of roughly spherical molecules), hopping between lattice sites i and j is commonly described using an Arrhenius-like rate.…”

“…For atomic and molecular systems (consisting of roughly spherical molecules), hopping between lattice sites i and j is commonly described using an Arrhenius-like rate. Here we employ the Clarke-Vvedensky bond-counting ansatz [35], which has been used in a variety of recent atomic [33,36,37] and C60 growth studies [18,22],…”