Non-destructive crystal rotation by shi impacts

We investigated the microstructure of single crystal NiO irradiated at 45° off-normal incidence by 593 MeV Au ions to a fluence of 1.4·10 ions/cm using electron microscope based techniques. It was found that the surface 11 μm thick layer experienced significant rotation along the direction of the incident ion beam projected onto the specimen surface while SAED showed the specimen as a whole remains single crystalline. Rotation vs depth profiles obtained from EBSD, TKD and SAED agreed well and suggests a maximum rotation of about 25° from the original <001> surface normal which is in agreement with on-line XRD measurement performed during irradiation. STEM microstructural analysis showed a high density of dislocations decorating the boundaries of nm sized cells exhibiting slight orientation differences. It was concluded that radiation induced stress buildup leads to the creation of low energy dislocation networks surrounding cells with minor orientation differences. These orientation differences are driven in along a specific direction due to unbalanced shear stress resulting from off normal irradiation and the residual stress from each thermal spike.