Regular silicon pillars and dichroic filters produced via particle-imprinted membranes

Abstract

We have produced regular silicon pillar arrays and porous gold films on the 100 nm scale without any optical or e-beam lithography. Using particle-assisted wetting we produced a nanoporous polymer membrane on silicon. The membrane incorporated a regular array of pores generated by embedding silica particles in an organic liquid and subsequently removing the particles after polymerization of the liquid. Gold vapor was deposited onto the silicon wafer coated by the porous polymer structure. This process created an array of gold dots on the substrate at the bottom of the pores, and at the same time, a sievelike porous gold layer on top of the polymer matrix. The top layer was lifted off and used as an optical short-pass filter. After removal of the polymer membrane, the remaining gold dot pattern on the substrate served as a mask in a deep reactive ion etching process. We obtain large-area arrays of silicon nanopillars up to 1.5 μm in height and below 200 nm in diameter.