Effect of helium-ion implantation on 3C -SiC nanomechanical string resonators

Hybrid quantum devices enable novel functionalities by combining the benefits of different subsystems. Particularly, point defects in nanomechanical resonators made of diamond or silicon carbide (SiC) have been proposed for precise magnetic field sensing and as versatile quantum transducers. However, the realization of a hybrid system may involve trade-offs in the performance of the constituent subsystems. In a spin-mechanical system, the mechanical properties of the resonator may suffer from the presence of engineered defects in the crystal lattice. This may severely restrict the performance of the resulting device and needs to be carefully explored. Here we focus on the impact of defects on high-Q nanomechanical string resonators made of prestressed 3C-SiC grown on Si(111). We use helium-ion implantation to create point defects and study their accumulated effect on the mechanical performance. Using Euler-Bernoulli beam theory, we present a method to determine Young's modulus and the prestress of the strings. We find that Young's modulus is not modified by implantation. Under implantation doses relevant for single-defect or defect-ensemble generation, both tensile stress and damping rate also remain unaltered. For a higher implantation dose, both exhibit a characteristic change.