Abstract
The plastic behavior of 6H SiC single crystals was studied by constant-rate compression tests between 1150°C and 1750°C and Knoop indentation tests between room temperature and 1400°C. Defects introduced by deformation were investigated with using a transmission electron microscope (TEM) operating at 1000kV. SiC crystals deformed mainly via glide of basal dislocations which were dissociated to Shockley partials. Owing to a low formation energy of basal stacking faults (evaluated to be 1.6mJ/m2 from the dissociation width), partials with high mobility can glide almost freely even when the mobility of their counterparts is limited. At temperatures below -800°C, glide of mobile partials leaving wide stacking faults behind them causes limited plasticity. Above -1000°C partial dislocations with lower mobility become mobile enough for dislocation multiplication and normal ductility is gained. The flow rate above 1150°C measured as a function of applied shear stress τ and temperature T was found to be proportional to (τ-τi)m+2 exp(-U/κT), where m=1.1±0.4, U=3.4±0.7eV and τi=3MPa. It was concluded from the stress exponent m-1 and dislocation morphology observed by TEM that dislocation motion is controlled by the Peierls mechanism.
