Self-Diffusion on Au(100): A Density Functional Theory Study
ABSTRACT We used density functional theory to detail new self-diffusion mechanisms on perfect and imperfect Au(100) surfaces. Herein, we report binding energies of stable intermediates and transition states lying on the potential energy surface for these systems. We report migration pathways in the presence of a variety of surface defects and along different step edges, explaining their energetics in terms of chemical bonding. Furthermore, diffusion rate constants are deduced, which are useful for both experimental verification and for implementation into large-scale kinetic Monte Carlo simulations.
SourceAvailable from: Aleix Comas-Vives[Show abstract] [Hide abstract]
ABSTRACT: We describe a multiscale modeling hierarchy for the particular case of Au-island ripening on Au(100). Starting at the microscopic scale, density functional theory was used to investigate a limited number of self-diffusion processes on perfect and imperfect Au(100) surfaces. The obtained structural and energetic information served as basis for optimizing a reactive forcefield (here ReaxFF), which afterwards was used to address the mesoscopic scale. Reactive force field simulations were performed to investigate more diffusion possibilities at a lower computational cost but with similar accuracy. Finally, we reached the macroscale by means of kinetic Monte Carlo (kMC) simulations. The reaction rates for the reaction process database used in the kMC simulations were generated using the reactive force field. Using this strategy, we simulated nucleation, aggregation, and fluctuation processes for monoatomic high islands on Au(100) and modeled their equilibrium shape structures. Finally, by calculating the step line tension at different temperatures, we were able to make a direct comparison with available experimental data.Advances in Physical Chemistry 01/2011; DOI:10.1155/2011/252591
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ABSTRACT: Growth regimes of gold thin films deposited by magnetron sputtering at oblique angles and low temperatures are studied from both theoretical and experimental points of view. Thin films were deposited in a broad range of experimental conditions by varying the substrate tilt angle and background pressure, and were analyzed by field emission scanning electron microscopy and grazing-incidence small-angle x-ray scattering techniques. Results indicate that the morphological features of the films strongly depend on the experimental conditions, but can be categorized within four generic microstructures, each of them defined by a different bulk geometrical pattern, pore percolation depth and connectivity. With the help of a growth model, a microstructure phase diagram has been constructed where the main features of the films are depicted as a function of experimentally controllable quantities, finding a good agreement with the experimental results in all the studied cases.Nanotechnology 01/2013; 24(4):045604. DOI:10.1088/0957-4484/24/4/045604 · 3.67 Impact Factor
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ABSTRACT: Ostwald ripening of metal islands has been investigated by kinetic Monte Carlo simulations using the results of quantum-chemical calculations and of the embedded atom method as input data. On Au(100) Ostwald ripening was found to be kinetically hindered at ambient temperatures. In contrast, small islands on Ag(100) decayed readily at uncharged and at positively charged surfaces. The rate of ripening increases both with temperature and with the surface charge. The latter effect is caused by the interaction of local dipole moments with the double-layer field. This work confirms and extends recent investigations of the effect of the field on the surface mobility of metal electrodes.Electrochimica Acta 07/2010; 55(19):5411-5413. DOI:10.1016/j.electacta.2010.04.066 · 4.09 Impact Factor