On the nature of defects created on graphene by scanning probe lithography under ambient conditions

The defects created by scanning probe lithography (SPL) under ambient conditions in CVD grown graphene were investigated using atomic force microscopy, micro-Raman (μ-RS) and micro-X-ray photoelectron spectroscopy (μ-XPS). Topographically, both protrusion and depression structures with distinguishable tribological properties were produced simultaneously. However, the key aspects of the spectroscopy were similar for the two topographies. μ-RS revealed that the ratio of the defect Raman peaks (ID/ID′) and the effective distance between defects (LD) had similar magnitude and dependence on the applied bias voltage. μ-XPS revealed no evidence of the generation of sp3-type defects. The small amplitude of the C–O peak and absence of CO and C–OH peaks, suggested a complete absence of graphene oxide in the defect areas. Our results indicate that similar defects are present in both depressions and protrusions and suggest that a common active mechanism, namely bond reconstruction, is responsible for both structures.