Figure 2. Scanning electron microscopy images of graphene before and after defect engineering.

Several nanopores were drilled in samples #1, #2 and #3 by the FIB system as seen in the yellow dashed line circles. The thermal conductivity of each modified graphene sample was then measured twice in opposite heat flow directions (shown by the red and green arrows). The big red arrows indicate the heat flow direction with the larger thermal conductivity, while the small green arrows indicate the opposite direction with the smaller thermal conductivity.