Soft Copper Nanoimprinting via Solid-State Electrochemical Etching for Flexible Optoelectronics

Patterned Cu is widely used for various electronic components, including metal interconnects. In the optoelectronic industry, high-resolution nanopatterning of Cu surfaces is commonly performed via photolithography, which requires photoresists and harsh chemicals. In this study, we developed a method for fabricating Cu nanopatterns based on solid-state electrochemical etching at the interface between a polymer electrolyte membrane (PEM) and Cu. The electrochemical reaction selectively ionized the Cu surface in contact with a patterned PEM stamp, allowing direct Cu patterning without using resists or harsh chemicals. This approach was successfully applied to produce patterns with resolutions of less than 100 nm and hierarchical structures. Such high-resolution metal patterns at the subwavelength scale (several hundred nanometers) enable the miniaturization of electrical circuits and the tuning of optical transmission/reflection spectra to enhance device surfaces. Semitransparent electrodes fabricated using nanopatterned Cu on poly(ethylene terephthalate) films exhibited good optical transmission and electrical resistance properties. The proposed PEM stamp-based solid-state electrochemical etching technique avoids the need for liquid electrolytes and resists, thereby offering a simple, low-cost, and environmentally friendly process for the direct nanopatterning of Cu.