Energetics of stacking boundaries on the {0001} surfaces of silicon carbide

Abstract

Silicon carbide often grows in the cubic phase under conditions where this is not the most stable phase. Ab initio calculations are presented which determine the energy of a stacking reversal at the ( 0001) and (000 1) surfaces of silicon carbide, and thus whether the cubic form is preferred in the vicinity of a free surface. In these calculations the surfaces are not reconstructed but hydrogen terminated, and care is taken to eliminate the spurious dipole-dipole interaction caused by the imposition of periodic boundary conditions, and also in estimating the amount of residual ionic relaxation. These calculations do show a clear distinction of 13 meV per surface pair between the silicon and carbon surfaces, although the results are not in complete agreement with experiment.

Tight-binding calculations of the band structure and total energies of the various polytypes of silicon carbide

“…19 are in better agreement with the energy differences from the DFT calculations of Cheng et al, 21 although the ordering of the polytypes is different. More recent results using DFT with pseudopotentials and a plane-wave basis 22 also show good agreement with the FP-LMTO calculations in Ref. 19.…”

“…The minimum energies for each structure are listed in Table I, along with our LAPW calculations and recent literature DFT calculation values. 14,19,22,38 It is clear from the table that the energy differences between polytypes are quite small, and that first-principles calculations disagree on the quantitative values. Even the ordering in energy and the ground state structure are not consistent among the different DFT calcu-lations.…”

Stacking Transformation from Hexagonal to Cubic SiC Induced by Surface Reconstruction: A Seed for Heterostructure Growth

“…The energy differences between the two polytypes were found to be rather small, so that the surface energy alone should not induce the modified stacking. Rutter and Heine [28] found a preference for a 60 ± rotation of the top bilayer, i.e., a hexagonal termination on a 3C-SiC surface again with only little energy decrease, yet without including superstructures in their calculations due to computational limitations. In earlier work by Heine et al [29], also for unreconstructed surfaces, a new layer was predicted to be attached in cubic stacking during growth, yet without considering the entropy term in the energy calculations.…”

Charged surfaces and slabs in periodic boundary conditions

“…A slab of silicon carbide cut along its {0001} planes lacks inversion symmetry and, if uncharged, will have a dipole moment perpendicular to the slab. For good convergence with cell size in the neutral system a self-consistent correction for this dipole moment is required [22]. In the following, two layers of a charged system are considered, again with an overall charge of +2e per unit cell.…”