Effect of grain size on the tensile mechanical behavior of single layer silicon germanide (SiGe): A molecular dynamics study

Due to the limitations of current fabrication methods, two-dimensional materials are rarely produced in a pristine form, and grain boundaries are inevitable during the fabrication and can skillfully alter the physical properties of materials. Therefore, it is essential to investigate the mechanical characteristics of two-dimensional materials thoroughly under consideration the effect of grains in order to create mechanically reliable devices. Large-scale molecular dynamics simulations were employed in this work to study the mechanical properties of 2D polycrystalline silicon germanide (SiGe) with grains ranging in size from 2 to 35 nm. We discovered that the pristine sheet of 2D SiGe shows the highest fracture stress of 93.8 GPa as well as the highest elastic modulus of 309.5 GPa. Results demonstrate that a reduction in grain size relates to an increase in fracture strain, although fracture strength exhibits an inverse relationship. The diminishing impact of the rising area density of flaws, which serves as an storage of stress-concentrating spots at the grain interface, may be partly to blame for the weakening fracture strength. However, for the largest average grain size 35 nm, we observed the fracture stress is 68.6 GPa, which is close to the pristine sample and elastic modulus of 193.7 GPa. For analytical purposes, we computed the potential energy per atom both for pristine and polycrystalline samples. Our findings will bring new insight into the mechanical instability problem for SiGe-based devices and will contribute to advancements in communication, energy conversion, and quantum computing in the near future.