Patterning Graphene Films by H₂O-Based Magnetic-Assisted UV Photolysis

Properly cutting graphene into certain high-quality micro-/nanoscale structures in a cost-effective way has a critical role. Here, we report a novel approach to pattern graphene films by H₂O-based magnetic-assisted ultraviolet (UV) photolysis under irradiation at 184.9 nm. By virtue of the paramagnetic characteristic, the photo-dissociated hydroxyl [OH(X²Π)] radicals are magnetized and have their oxidation capability highly enhanced through converting into an accelerated directional motion. Meanwhile, the precursor of H₂O(X̃¹A₁) molecules distributes uniformly thanks to its weak diamagnetic characteristic, and there exists no instable diamagnetic intermediate to cause lateral oxidation. Possessing these unique traits, the H₂O-based magnetic-assisted UV photolysis has the capability of making graphene microscale patterns with the linewidth down to 8.5 μm under a copper grid shadow mask. Furthermore, it is feasible to pattern graphene films into 40 nm-wide ribbons under ZnO nanowires and realize hybrid graphene/ZnO nanoribbon field-effect transistors with a hole mobility up to 7200 cm²·V^-1·s^-1. The X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry analyses reveal that OH(X²Π) radicals act as a strong oxidant and that another product of H(1²S) adsorbs weakly on graphene.