A self-aligning microtensile setup: Application to single-crystal GaAs microscale tension-compression asymmetry

Abstract

A novel microtensile setup was developed to overcome typical issues encountered in small-scale testing, particularly sample fabrication, sample handling, and misalignment. The system features a silicon (Si) gripper, which is able to self-align with the specimen main axis. Finite element simulations were employed to optimize the microtensile specimen geometry and to mechanically characterize the system. Specimens were prepared using focused ion beam milling, while reactive ion etching was employed to produce the grippers. The system was calibrated using single-crystal (100) Si specimens. The strength asymmetry of brittle crystals was investigated on the example of gallium arsenide (GaAs). Microtensile GaAs specimens and square micropillars sharing lowest dimensions of 1.70 ± 0.19 μm were tested along the [001] crystallographic orientation. Micropillars underwent plastic deformation via twinning in {111} planes and exhibited yield stress of 2.60 ± 0.14 GPa. The tensile experiment showed brittle failure at 1.86 ± 0.17 GPa associated with complex fracture surfaces and no measurable dislocation activity.