Two-dimensional arrangement of CH3NH2 adsorption on Si(0 0 1)-2 × 1

The adsorption of CH3NH2 on Si(0 0 1)-2 × 1 is investigated using density functional theory slab calculations. When the CH3NH2 coverage is greater than 0.5 ML, we find that the adsorption energetics alter significantly due to a combination of: (i) adsorbate–adsorbate repulsive interactions, (ii) adsorbate-induced electronic structure changes of neighboring dimers, and (iii) hydrogen-bonding interactions. Our calculations show that, among them, adsorbate–adsorbate repulsion plays a major role in determining the two-dimensional ordering of CH3NH2 adsorption at the full coverage of 1.0 ML, leading the zigzag structure to be energetically more favorable than the aligned structure along the dimer row.