The Relationship between Activation Parameters and Dislocation Glide in 4H-SiC Single Crystals

4H-SiC single crystals were deformed by compression in the temperature range 550 to 1300 °C and a strain rate range of 3.1 × 10–5 to 6.5 × 10–4 s–1 to determine the critical resolved shear stress for slip on the 〈 2-1-10〉(0001) primary slip system. Two different methods to determine the activation parameters for dislocation glide were examined. In the first method, where the activation enthalpy for dislocation glide ΔHg is assumed to be a function of the applied stress τ, ΔHg drops from ∼7.4 eV at τ ≈︂ 8 MPa to ∼2.8 eV at τ ≈︂ 235 MPa. In the second method, where the activation enthalpy for dislocation glide, Q, is assumed to be stress-independent, the values determined at strain rates of less than 6.3 × 10–5 s–1 were Q ≈︂ (2.1 ± 0.7) eV at low temperatures (T < 1100 °C) and Q ≈︂ (4.5 ± 1.2) eV at high temperatures (T > 1100 °C). Transmission electron microscopy investigations of the deformed samples show that very different configurations of dislocations are activated under the action of the applied stress. At 1300 °C, the dislocations were all perfect, albeit dissociated into leading/trailing partials separated by a ribbon of stacking fault, while at 700 °C only single leading partials, each dragging a stacking fault and without their corresponding trailing partials, were observed.