Optical properties of high-quality nanohole arrays in gold made using soft-nanoimprint lithography
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lasmonics, Photonics, and Metamaterials Research Letter
Optical properties of high-quality nanohole arrays in gold made using soft-nanoimprint lithography M.A. Verschuuren, Philips Research, High Tech Campus 4, 5656 AE, Eindhoven, The Netherlands M.J.A. de Dood, and D. Stolwijk, Huygens Laboratory, P.O. Box 9504, 2300 RA, Leiden, The Netherlands G.W. ‘t Hooft, Philips Research, High Tech Campus 4, 5656 AE, Eindhoven, The Netherlands; Huygens Laboratory, P.O. Box 9504, 2300 RA, Leiden, The Netherlands A. Polman, Centre for Nanophotonics, FOM Institute AMOLF, Science Park 104, 1098 XG Amsterdam, The Netherlands Address all correspondence to A. Polman at [email protected] (Received 2 July 2015; accepted 2 November 2015)
Abstract We present a novel soft-nanoimprint procedure to fabricate high-quality sub-wavelength hole arrays in optically thick films of gold on glass substrates. We fabricate 0.5 × 0.5 mm2 structures composed of a square array of 180 nm-diameter holes with a 780 nm pitch. Optical angular transmission measurements on the arrays show clear extraordinary transmission peaks corresponding to the dispersion of surface plasmon polaritons propagating on either side of the metal film. The transmission features can be strongly controlled by engineering the dielectric environment around the holes. As the nanoimprint procedure enables fabrication of nanoscale patterns over wafer-scale areas at low cost, these imprinted metal nanoparticle arrays can find applications in, e.g., optical components, photovoltaics, integrated optics, and microfluidics.
Introduction Metal films perforated with an array of sub-wavelength holes have intrigued researchers since the discovery that these arrays show extraordinary transmission of light.[1–4] The enhanced transmission is mediated by surface plasmon polaritons (SPPs) that are excited at the metal surface by diffraction form the array. Arrays of nanoholes find many different applications such as, e.g., in color filters[5] nanoscale light concentrators for application in bio-sensors,[6] and in solar cells.[7,8] To realize applications at a large scale, a fabrication method is required that is able to pattern hole arrays with designed geometry, hole size, and pitch at large area and at low cost. Nanohole arrays in metal films are often made using focused ion beam (FIB) milling of a metal film, or by electron beam lithography in combination with metal lift-off, which are both relatively slow and expensive fabrication techniques. Interference lithography in combination with liftoff is also being used, but is limited to the fabrication of patterns with a fixed period. Moreover, a disadvantage of the metal lift-off procedure is that it often requires the use of a thin (2–5 nm) adhesion layer of titanium or chromium, which strongly absorbs surface plasmons. Furthermore, the lift-off process releases a large density of metal dots, some of which typically adhere to the array, causing imperfect patterns that reduce the optical performance of the array. Recently, nanoimprint lithography[9,10] was int
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