One-Dimensional Pattern Formation of Adsorbed Molecules on the Ge(100)-2 × 1 Surface Driven by Nearest-Neighbor Effects

Formations of distinct one-dimensional patterns along the dimer row have been reported in methanol and ethylene adsorption on the germanium(100)-2 × 1 surface. A theoretical investigation is carried out in this study to provide a unified explanation of the pattern formation. Density functional theory calculation results show that an existing adsorbate affects the adsorption kinetics of the adjacent dimer, an effect that is mostly confined to the nearest neighbor. Kinetic Monte Carlo simulations are performed with the calculated kinetic parameters. The simulation results agree well with the experimental observations of ethylene and methanol adsorption on Ge(100), showing that the nearest-neighbor effect leads to longer-range pattern formation. The modeling is extended to the Si(100) surface where a similar pattern as on Ge(100) was formed with ethylene but not with methanol, and it can be further applied to spontaneous adsorbate patterning on ordered surfaces.