Close inspections of defect structures in friction with a probe radius of 8 nm. The scratching depth is 0.82 nm. (a,c) Bottom views of defect structures at penetration depths of 0.72 and 0.82 nm, respectively. Atoms are colored according to their BAD values and FCC atoms are not shown. (b,d) Dislocation networks shown in (a) and (c), respectively. (e,f) Dislocation networks after the completion of scratching and retraction, respectively.