Kinetic Monte Carlo study of the effects of hydrogen on the 3-D epitaxial growth of Ni(100) and Ni(110)

The effects of hydrogen on Ni(100) and Ni(110) homoepitaxy, up to 0.7 and 1.1 monolayers depositions, respectively, have been investigated by kinetic Monte Carlo (KMC) methods used to simulate the surfaces growth. A selection of the set of rate constants for the mobility of adsorbed Ni atoms in various surface island configurations, with and without the presence of a small amount of hydrogen impurity, is also reported on here. On the Ni(100) surface we find that the presence of highly mobile H atoms has measurable effects on the size and shape of the Ni island formation. Without the presence of H, the Ni(100) surface growth shows much more extensive roughening than does the Ni(110) surface, and this difference is traced to the axis asymmetry. With the presence of H atoms, the Ni(100) surface roughness is substantially lessened, showing larger islands and flatter islands. Comparisons are also made to the Ni(110) surface, where layer-by-layer growth dominates with or without the presence of H atoms, which is found to have very modest effects on both island size and roughness. For both the Ni(100) and (110) surfaces, the kinetically determined island morphologies at the sub-to-near monolayer level occur over time periods that are long on the deposition time scale, and therefore the morphology differences can become frozen in place.