A kinematically driven growth mechanism; AlF3 on Cu(100)

FERRÓN, J.; GÓMEZ, L.; MARTIN, V.; GARCES, J.

Paris

Conferencia; |19th International Vacuum Congress IVC-19; International Conference on Nanoscience and Technology ICN+T 2013; 15th International Conference on solid surfaces ICSS-15; 2013

IUVSTA

The growth of aluminum fluoride (AlF3) on copper single crystal, Cu(100) face, is characterized by several anomalous features. Among them, we have a large diffusion path length at room temperature, nucleation at both sides of steps and island atomistic arrangement along special directions [1, 2]. In this work we introduce a new diffusion model based only on kinematic properties that allows us to explain all the particular properties of this system. The model is based in the rearrangement of a bi-molecules (Al2F6) trying to resemble its vacuum behavior. This rearrangement breaks the expected random trajectories of a molecule diffusing over a surface, privileging not only one diffusion direction but also its sense of movement. Additionally, the contact surface is minimized increasing the surface diffusivity. The model is supported by two different calculations, i.e. Monte Carlo simulations based on empirical potentials [3] and Density Functional Theory (DFT) calculations. In the figure we depict the different structures obtained from DFT as well as their corresponding energies. The structure corresponding to the minimum energy is the responsible of the breaking of the random pathway, as well as of the particular features of the AlF3 growing system.