Enhanced nucleation of Al islands on H-dosed Si(100)-2 × 1 surface: A combined density functional theory and kinetic Monte Carlo study

Using a combined density functional theory (DFT) and kinetic Monte Carlo (kMC) approach, we show that the presence of small dose of hydrogen atoms on Si(100)-2 × 1 surface can increase Al chain density by as much as four times compared to the clean Si(100)-2 × 1 value. Though the observed enhanced nucleation can be explained by trapping of Al adatoms by H and their subsequent stabilization into islands, we find that a similar increase in island density can be achieved even when H merely blocks (but does not trap) Al adatoms. For H-bound islands, our DFT analysis suggests that Al adatoms are pinned preferentially on one side of H. Additionally, we argue that despite the high ratio of diffusion to adsorption rates which should favor H-bound islands over homogeneously nucleated islands, the former is not as numerous conventional nucleation theory would predict.