Photoplastic near-field optical probe with sub-100-nm aperture made by replication from a nanomold
G. M. Kim, B. J. Kim , E. ten Have, F. Segerink, N. F. van Hulst, and J. Brugger.
J. of Microscopy-Oxford Vol.209, Pt 3, pp. 267-271, 2003
Polymers have the ability to conform themselves to surface contours down to few nanometers. We studied the filling of transparent epoxy-type EPON SU-8 into nanoscale apertures made in a thin metal film as a new method for polymer/metal nearfield optical structures. Mold replica processes combining silicon micromachining with the photo-curable SU-8 offer great potential for low-cost nanostructure fabrication. Besides offering a route for mass-production the transparent pyramidal probes are expected to improve light-transmission thanks to a wider geometry near the aperture.
By combining silicon MEMS, mold geometry tuning by oxidation, anti-adhesion coating by self-assembled monolayer (SAM), and mechanical release steps, we propose here an advanced method for near-field optical probe fabrication.
The major improvement is the possibility to fabricate nanoscale apertures directly on wafer scale during the micro-fabrication process and not on free-standing tips. Optical measurements were performed with the fabricated probes. The full width half maximum (FWHM) after Gaussian fit of intensity profile indicates a lateral optical resolution of around 60 nm.
SNOM image of single molecules taken by fabricated probe (scanning area 1.8 x 1.8μm2) and intensity profile of molecule 4. The signal-to-noise ratio is about 2 and the FWHM of the fitted intensity profile is about 60 nm.