Effect of sulfur passivation on 6H-SiC surface stability

Based on first-principles calculation, the surface stability of S-passivated 6H-SiC in different terminals are researched through investigating surface energy, charge distribution and density of states with the change of sulfur coverage from1/4 monolayer (ML) to 1 monolayer (ML). Our calculations show that S-passivated Si-terminal surface performs better than Si-terminal surface. Surface-state of 6H-SiC is reduced by about 1-4 electrons/eV due to S passivation. Meanwhile as the sulfur coverage increasing, surface energy is decreased from about -5.2eV/nm² to about -40 eV/nm² which leads to a more stable structure. According to theoretical calculation and mechanism analysis, the most stable structure is 3/4 ML sulfur atoms absorb in bridge site on Si-terminal surface.