Nanogap-Assisted Surface Plasmon Nanolithography

Nanoparticles of noble metals exhibit localized surface plasmons (LSP) associated with enhancement of the electromagnetic field due to its localization in nanometric domains at the surface of nanoparticles. Especially, nanogap metallic structures show strong enhancement of the electromagnetic field at the nanogap position. This can be achieved up to 10 5 times larger than the incident light field. We have explored the possibility to use the localized field for nanogap-assisted surface plasmon nanolithography. For this purpose, monodisperse arrays consisting of pairs of rectangular gold nanoblocks separated by nanogaps were fabricated on glass substrates using electron beam lithography and lift-off techniques. Nanoblock structures were used as photomasks for contact exposure of thin films of positive photoresist on glass substrates. Thus, ordered clusters of nanoparticles separated by nanogaps can provide a stable and versatile platform for further development of optical subwavelength nanolithography. To the best of our knowledge, this is the first proof-of-principle demonstration of such a technique.