Metal/metal homoepitaxy on fcc(111) and fcc(001) surfaces: Deposition and scattering from small islands

Abstract

For systems of a single chemical species, we investigate the dynamics of adsorption of a metal atom on a clean fcc(111) metal substrate and on a pyramidal defect built on the fcc(001) substrate; the defect extends three layers above the surface, with nine, four, and one atoms in each layer, respectively. Each face thus forms a small part of an fcc(111) face. Molecular dynamics (MD) simulations are used where the interaction energy and the corresponding forces are generated from the recently developed non-self-consistent density functional based corrected effective medium (CEM) method in its simplest and computationally most efficient semiempirical MD/MC-CEM formulation. In previous work, the MD/MC-CEM form has been shown to predict the geometric and energetic properties of clean and adsorbate covered surfaces accurately. We show that there is no transient mobility for the Cu/Cu(111) system at a surface temperature of 80 K and an incident gas atom kinetic energy of 0.25 eV at incident angles up to 45° from the surface normal. This finding should hold for other homogeneous metal deposition systems since it arises from the fact that energy dissipation to the metal substrate is so efficient. For the Cu system, we determine that the cross section for sticking on the sides of the 14 atom pyramid varies from 9.0 to 37.2 Å2 for two MD/MC-CEM based potential energy surfaces (PES) differing only in the energetics of low coordination binding. Normalized to the aiming area, these give probabilities of 8.6% to 35.7%. Thus, it is shown that the low coordination region of the interaction strongly impacts the determination of growth modes, shifting from a funneling method giving two-dimensional (2D) layer by layer growth to a 3D mode, producing a rougher surface.