Stacking fault energy of 6H-SiC and 4H-SiC single crystals

Single crystal 4H and 6H polytypes of SIC have been deformed in compression at 1300 degrees C. All the deformation-induced dislocations were found to be dissociated into two partials bounding a ribbon of intrinsic stacking fault. Using two-beam bright-field and weak-beam dark-field techniques of transmission electron microscopy, the stacking fault energy of these two SiC polytypes has been determined from the separation width of the two partials of dissociated dislocations. The stacking fault energy of 4H-SiC is determined to be 14.7 +/- 2.5 mJ m(-2), and that of 6H-SiC to be 2.9 +/- 0.6 mJ m(-2). As a verification, the stacking fault energy of 4H-SiC has been determined also from the minimum radius of curvature of extended nodes. This latter method gave a value of 12.2 +/- 1.1 mJ m(-2) which is within the range determined from measurement of partial dislocation separations. The experimental values of stacking fault energy for 4H- and 6H-SiC have been compared with estimates obtained from a generalized axial next-nearest-neighbour Ising (ANNNI) spin model. It is found that the theoretical models predict the lower stacking fault energy of 6H-SiC compared with that of 4H-SiC, and the predicted energies are, respectively, within 5% and 40% of the experimental values.