SiO₂ Electret Formation by Electrode-Free Electrochemical Nanolithography: A Chemophysical Surface Functionalisation

This work introduces a new method for creating patterned SiO₂ electrets using Electrode-Free Electrochemical Nanolithography (EFEN), enabling surface functionalisation without direct electrode contact. EFEN applies an alternating current through capacitive coupling between a conductive stamp and an insulating substrate in high-humidity conditions, forming a nano-electrochemical cell that drives localised reactions. Using thermally grown SiO₂ films, we achieve submicrometre patterning with minimal topographical impact but significant electronic alterations. Characterisation via Kelvin Probe Force Microscopy and Electric Force Microscopy confirms the formation of charged regions replicating the stamp pattern, with adjustable surface potential shifts up to –1.7 V and charge densities reaching 300 nC·cm⁻². The process can be scaled to areas of 1 cm² and is compatible with conventional laboratory equipment, offering a high-throughput alternative to scanning-probe lithography. EFEN combines simplicity, accuracy, and scalability, opening new opportunities for patterned electret production and functional surface engineering.