Ab Initio Studies of the Surface Reaction of Si2C and SiC2 with Si on the 4H-SiC (000-1) Surface
The origin of the polytypes of SiC has been investigated from the viewpoint of surface reactions by the density functional theory (DFT) within the Projector Augmented Wave-Generalized Gradient Approximation. Three radicals were considered here as the major species in the crystal growth process: Si, Si2C and SiC2. We supposed that these radicals contribute to the crystal growth directly through the adsorption on the 4H-SiC (000-1) C-face surface. The DFT calculations showed that the Si2C, which relatively has a similar structure with the SiC crystal, had no activation barrier to be adsorbed chemically to the 4H-SiC C-face surface. On the other hand, SiC2 with Si showed an activation barrier of 0.79eV to form the 4H-SiC crystal. In order to investigate the arrangements to decide polytypism in SiC, we compared the adsorption energies between the different sites, which correspond to the 4H-SiC crystal and a disordered arrangement. The activation energies had almost no difference. Our calculations indicated that these radicals do not contribute to the origin of the polytypes of SiC.
Robert P. Devaty, David J. Larkin and Stephen E. Saddow
H. Yamaguchi et al., "Ab Initio Studies of the Surface Reaction of Si2C and SiC2 with Si on the 4H-SiC (000-1) Surface", Materials Science Forum, Vols. 527-529, pp. 235-238, 2006