Figure 10.

2-D AFM images showing localized hole defects and shape of FLG folding. (a) The localized hole defects after Ar⁺ ion irradiation of 1.5 keV. (b) Triangle shape of FLG folding (enclosed by a circle), multi-layer folding (indicated by white arrow), wrinkles (indicated by black arrow) and isolated particles (enclosed by a rectangle) after 4.5 keV ion irradiation.