Ab-initio Calculations of Energies and Self-Diffusion on Flat and Stepped Surfaces of Al and their Implications on Crystal Growth

TL;DR

This study uses density-functional theory to analyze energies and diffusion behaviors of aluminum surfaces and steps, revealing insights into atomic interactions and energy barriers relevant to crystal growth.

Contribution

It provides detailed ab-initio calculations of surface and step formation energies, adsorption preferences, and diffusion barriers on aluminum surfaces, including stepped and flat regions.

Findings

Al(111) surface favors hcp adsorption site slightly over fcc.

Self-diffusion barrier on Al(111) is very low (0.04 eV).

Adatoms are attracted to step edges with an electronic-origin potential.

Abstract

Using density-functional theory we investigate several properties of Al(111), Al(100), Al(110), and stepped Al(111) surfaces. We report results of formation energies of surfaces, steps, adatoms, and vacancies. For the adsorption and diffusion of Al on flat regions of Al(111) surfaces we find the hcp site energetically slightly preferred over the fcc site. The energy barrier for self-diffusion on Al(111) is very low (0.04eV). Coming close to one of the two sorts of close packed, monoatomic steps on Al(111), labeled according to their {111} and {100} micro-facets, Al adatoms experience an attraction of <~ 0.1eV already before direct contact with the edge of the step. This attraction has a range of several atomic spacings and is of electronic origin. Upon arrival at the lower step edge, the adatom attaches with no barrier at a low energy five-fold coordinated site. Coming from the upper terrace, it incorporates into the step by an atomic exchange process, which has a barrier below 0.1eV for both sorts of close packed steps. The barrier for diffusion ...