Fabrication of single-layer metamaterials with sub-50-nm ultrasmall gaps

Metamaterials are artificial electromagnetic structures that can have a negative refractive-index, not available in nature. Until now, many different structures have been investigated and considerable approaches have been realized. However, fabrication of metamaterials is still a critical issue due to the difficulty of etching metals especially when the structure dimension is reduced. In this letter, we demonstrate the development of fabricating metamaterials with ultrasmall gap apertures. Novel geometries fabricated in optically thick metallic films are shown. Nanorod structures with different shapes are also developed. Common problems for FIB milling like redeposition and tapered profiles are discussed.