5 nm Nanogap Electrodes and Arrays by Super-resolution Laser Lithography

The development of reliable, mass-produced, and cost-effective sub-10 nm nanofabrication technology leads to an unprecedented level of integration of photonic devices. In this work, we describe the development of a laser direct writing (LDW) lithography technique with ∼5 nm feature size, which is about 1/55 of the optical diffraction limit of the LDW system (405 nm laser and 0.9 NA objective), and the realization of 5 nm nanogap electrodes. This LDW lithography exhibits an attractive capability of well-site control and mass production of ∼5 × 10⁵ nanogap electrodes per hour, breaking the trade-off between resolution and throughput in a nanofabrication technique. Nanosensing chips have been demonstrated with the as-obtained nanogap electrodes, where controllable surface enhancement Raman scattering of rhodamine 6G has been realized via adjusting the gap width and, especially, the applied bias voltages. Our results establish that such a low-cost and high-efficient lithography technology has great potential to fabricate compact integrated circuits and biochips.