Electrode-Free Anodic Oxidation Nanolithography of Low-Dimensional Materials.

Scanning probe lithography based on local anodic oxidation (LAO) provides a robust and general nanolithography tool for a wide range of applications. Its practical use, however, has been strongly hampered due to the requirement of a prefabricated microelectrode to conduct the driving electrical current. Here we report a novel electrode-free LAO technique, which enables in situ patterning of as-prepared low-dimensional materials and heterostructures with great flexibility and high precision. Unlike conventional LAO driven by a direct current, the electrode-free LAO is driven by a high-frequency (>10 kHz) alternating current applied through capacitive coupling, which eliminates the need of a contacting electrode and can be used even for tailoring insulating materials. Using this technique, we demonstrated flexible nanolithography of graphene, hexagonal boron nitride, and carbon nanotubes on insulating substrates with ∼10-nanometer precision. In addition, the electrode-free LAO exhibits high etching quality without oxide residues left. Such an in situ and electrode-free nanolithography with high etching quality opens up new opportunities for fabricating ultraclean nanoscale devices and heterostructures with great flexibility.