Catalytic Role of Gold Nanoparticle in GaAs Nanowire Growth: A Density Functional Theory Study

The energetics of Ga, As, and GaAs species on the Au(111) surface (employed as a model for Au nanoparticles) is investigated by means of density functional calculations. Apart from formation of the compound Au7Ga2, Ga is found to form a surface alloy with gold with comparable ΔH ∼ −0.5 eV for both processes. Dissociative adsorption of As2 is found to be exothermic by more than 2 eV on both clean Au(111) and AuGa surface alloys. The As–Ga species formed by reaction of As with the surface alloy is sufficiently stable to cover the surface of an Au particle in vacuo in contact with a GaAs substrate. The results of the calculations are interpreted in the context of Au-catalyzed growth of GaAs nanowires. We argue that arsenic is supplied to the growth zone of the nanowire mainly by impingement of molecules on the gold particle and identify a regime of temperatures and As2 partial pressures suitable for Au-catalyzed nanowire growth in molecular beam epitaxy.