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

Abstract

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.

Determination of the controlling parameters for dislocation nucleation in SrTiO3: An investigation by nanoindentation

“…40,52 Considering that the lattice constant (c) of STO is ∼3.905 Å and the corresponding atomic volume is c 3 , 54 and that the values of the determined V are all smaller than the volume of one atomic, it can be concluded that point-like substance was participated in the dislocation nucleation process. This scenario is similar to the arguments derived by Stich et al on the (0 0 1)-oriented STO, 22 Dong et al on the GaN single crystals, 55 Qiu et al on KDP single crystal, 56 and Ma et al on LiTaO 3 single crystal. 57 That is, the dislocation nucleation is possibly determined by the quantity and mobility of mobile dislocation sources.…”

“…on the (0 0 1)‐oriented STO, 22 Dong et al. on the GaN single crystals, 55 Qiu et al. on KDP single crystal, 56 and Ma et al.…”

Effects of Ion Irradiation and Temperature on Mechanical Properties of GaN Single Crystals under Nanoindentation

“…The pop-in phenomena (sudden displacement jump) in P-h curves are observed at shallow indentation depths (Figure 2). Similar pop-in phenomena have been observed in nanoindentation of GaN single crystals [13,29,30], GaN thin films on substrates [31], and The pop-in phenomena (sudden displacement jump) in P-h curves are observed at shallow indentation depths (Figure 2). Similar pop-in phenomena have been observed in nanoindentation of GaN single crystals [13,29,30], GaN thin films on substrates [31], and as well as many other brittle semiconductor materials (e.g., Si, InP, ZnO, and GaAs) [32].…”

“…Similar pop-in phenomena have been observed in nanoindentation of GaN single crystals [13,29,30], GaN thin films on substrates [31], and The pop-in phenomena (sudden displacement jump) in P-h curves are observed at shallow indentation depths (Figure 2). Similar pop-in phenomena have been observed in nanoindentation of GaN single crystals [13,29,30], GaN thin films on substrates [31], and as well as many other brittle semiconductor materials (e.g., Si, InP, ZnO, and GaAs) [32]. The first pop-in events in GaN single crystals under nanoindentation are associated with the critical transition from pure elastic behavior to plastic deformation [14] and are usually attributed to dislocation nucleation and propagation during loading [32].…”

“…Eve et al [12] investigated the pile-up, hardness, and Young's modulus of GaN films irradiated with swift heavy uranium ions. More recently, our research explored the statistics of pop-in events of GaN single crystals irradiated by 3 MeV C + ions, identifying a linear relationship between the regression slop as a micromechanical characterization and the hardness [13]. However, these studies have yet to address the influence of elevated temperature on the mechanical properties of ion-irradiated GaN.…”