Termination dependence of surface stacking at4H-SiC(0001)−1×1: Density functional theory calculations

Abstract

We study the effect of adsorbates on the relative stability of hexagonal and cubic stacking sequences at the topmost SiC bilayers of $4H\text{-SiC}(0001)\text{\ensuremath{-}}1\ifmmode\times\else\texttimes\fi{}1$ surfaces using first-principles calculations. We investigate F-terminated, OH-terminated, H-terminated, and clean surfaces, and in all cases, the cubic structure is more stable than the hexagonal structure. The energy difference between the two structures, however, significantly depends on adsorbates and is largest on the clean surface while it is smallest on the H-terminated surface. Stabilization of the cubic structure at F-terminated and OH-terminated surfaces is in contradiction to a simple argument based on the electrostatic interaction and we attribute it to orbital hybridization between occupied states of adsorbates and unoccupied states of the substrate surface. The present results suggest a possible means of controlling step bunching and the SiC stacking sequence by surface adsorbates.