Defects created in N-doped 4H-SiC in the brittle regime: Stacking fault multiplicity and dislocation cores

Abstract

Defects introduced in N-doped 4H-SiC by surface scratching and bending at 823 K or 973 K were characterised by weak beam-dark field transmission electron microscopy (TEM), high-resolution TEM (HRTEM), large-angle convergent beam electron diffraction (LACBED), image analysis and dislocation core reconstructions. They consist of double stacking faults (DSFs) dragged by partial dislocation (PD) pairs in planes in which the Si–C dumbbells have the same orientation. The PDs forming a pair always have the same Burgers vectors. The reconstructions prove that their core composition depends on the dislocation character, the expansion direction and the orientation of the dumbbells in the glide planes. Only Si(g) are mobile, the lack of mobility of C(g) explaining why only three kinds of half-loops expand and why one DSF is always edged by two identical PDs. It is shown that the line morphology is not a sufficient criterion to determine the core composition. Although mechanical stresses were applied, additional thermodynamic and/or electronic driving forces influenced the DSF formation in our experiments.