Surface energy of Si(110)- and 3C-SiC(111)-terminated surfaces

We perform total-energy electronic-structure calculations based on density functional theory in the framework of the local density approximation to discuss the surface energy convergence of non-polar Si(110)- and polar 3C-SiC(111)-terminated surfaces. Whilst the non-polar surface show monotonic convergence in surface energy, the polar surface is oscillatory. The relaxations of 3C-SiC(111)- and -6H(0001)-terminated surfaces are very similar; however, the two structures are electronically different due to differences in the relative energetic positions of their dangling bonds. Comparing the energetic positions of the dangling bonds, the calculation revealed that the carbon dangling bond is about 1.32 eV lower in energy than that of silicon in the 3C-terminated surface. Again, the presence of these dangling bond states makes both polar and non-polar surfaces show metallic behaviour, as indicated in their respective dispersion curves.