Gold Films with Imprinted Cavities

Nanostructured metal films may exhibit localized plasmon resonances that are of great interest due to their potential use in sensors and other photonic devices. In this Letter, we employ a general and versatile method for fabricating metal films with imprinted cavities using a combination of colloidal lithography, template stripping, and plasma etching. We demonstrate the procedure in the fabrication of 40 nm thick gold films containing varying densities of imprinted 100 nm spherical cavities. The plasmon energy of the cavity, mode is Investigated spectroscopically and exhibits sensitivity to refractive index changes in the cavity interior. Using microcontact stripping to generate confined patterns of cavities, we establish a direct correlation between optical dark field and AFM images of single and clustered cavities. The results demonstrate the applicability of single imprinted cavities as highly localized refractive index sensors.