Strain buildup in 4H-SiC implanted with noble gases at low dose
Résumé
4H-SiC single crystals were implanted at room temperature (RT) and at 673 K with different noble gases in a low dose regime. Strain buildup has been systematically investigated based on X-ray diffraction analysis. At RT the strain increase with dose is linear up to amorphization. With increasing temperature, 673 K, the accumulation shows a two-step shape. The first step can be anticipated by using the direct impact model independent of incident ions. Beyond a critical dose, a second step of strain is observed with an accumulation scenario related to the creation of defects, cascade overlapping and their enhanced stability via their interaction with gas. At low dose, the strain recovery under annealing is a thermally activated process whose underlined mechanisms are similar to those of dynamic recovery. Moreover, the surface swelling is closely related to this implantation-induced elastic strain. At RT, the hardening effect of about 10% has been confirmed at low dose. The increase of fracture toughness as well as hardness changes under implantation seems to be related to the increase of the in-plane stresses and to the nucleation/ pinning of dislocation via the generation of point-like defects.