Onset of plasticity in a Σ = 5 GaAs compliant structure

Compliant structures have been fabricated in which a thin GaAs layer (thickness between 10 and 20nm) was bonded on top of a GaAs substrate with a large twist angle (about 37). This twist angle value was chosen so that the energy of the boundary (coincident boundary of type =5 (001)) was minimized. The structure of the interface was characterized and the onset of plasticity in such a compliant substructure was investigated using nanoindentation that allowed the low-load deformation regime to be observed. The results are compared with those obtained under the same conditions on a GaAs bulk substrate alone. No plastic zone was observed by transmission electron microscopy in the compliant structure under loads below 0.25mN while, under the same loads, plastic deformation was observed in the bulk substrate. For higher loads (2mN), plastic-flow enhancement was observed in the compliant structure. The results are discussed in the light of the arrangement of dislocations observed in the plastic zones.