Mechanical Properties of GaN Single Crystals upon C Ion Irradiation: Nanoindentation Analysis

Mechanical properties of gallium nitride (GaN) single crystals upon carbon ion irradiation are examined using nanoindentation analysis at room temperature. Pop-in events in the load-depth curves are observed for unirradiated and irradiated GaN samples. A statistical linear relationship between the critical indentation load for the occurrence of the pop-in event and the associated displacement jump is exhibited. Both the slope of linear regression and the measured hardness increase monotonically to the ion fluence, which can be described by logistic equations. Moreover, a linear relationship between the regression slope as a micromechanical characterization and the hardness as a macroscopic mechanical property is constructed. It is also found that the maximum resolved shear stress of the irradiated samples is larger than that of the unirradiated samples, as the dislocation loops are pinned by the irradiation-induced defects. Our results indicate that the nanoindentation pop-in phenomenon combined with a statistical analysis can serve as a characterization method for the mechanical properties of ion-irradiated materials.

Automated summary

In this study, the mechanical properties of GaN single crystals upon carbon ion irradiation were investigated using nanoindentation analysis. It was found that a linear relationship exists between the critical indentation load for the occurrence of pop-in events and the associated displacement jump. Both the regression slope and the hardness increased monotonically with ion fluence, which can be described by logistic equations. Additionally, a linear relationship was established between the regression slope as a micromechanical characterization and the hardness as a macroscopic mechanical property. It was also observed that the irradiated samples had a higher maximum resolved shear stress compared to the unirradiated samples due to the pinning of dislocation loops by irradiation-induced defects. These results suggest that the nanoindentation pop-in phenomenon, combined with statistical analysis, can be used as a characterization method for the mechanical properties of ion-irradiated materials.