Monocrystalline 4H and 6H polytypes were deformed in compression at 1300C. All of the deformation-induced dislocations were found to be dissociated into 2 partials which bounded a ribbon of intrinsic stacking fault. By using 2-beam bright-field and weak-beam dark-field techniques of transmission electron microscopy, the stacking-fault energy of these two polytypes was deduced from the separation width of the 2 partials of the dissociated dislocations. The stacking-fault energy of 4H-material was deduced to be 14.7mJ/m2, while that of 6H-material was 2.9mJ/m2. As a check, the stacking-fault energy of 4H-material was also deduced from the minimum radius of curvature of extended nodes. The latter method gave a value of 12.2mJ/m2; which was within the range that was determined from measurements of partial dislocation separations. The experimental values of stacking-fault energy for 4H and 6H material were compared with estimates that were obtained by using a generalized axial next-nearest neighbour Ising spin model. It was found that the theoretical models predicted a lower stacking-fault energy for 6H-material; as compared with that for 4H-material. The predicted energies were within 5 and 40%, respectively, of the experimental values.

Stacking Fault Energy of 6H-SiC and 4H-SiC Single Crystals M.H.Hong, A.V.Samant, P.Pirouz: Philosophical Magazine A, 2000, 80[4], 919-35