title: Improved focused ion beam fabrication of near-field apertures using a silicon nitride membrane.
abstract: We report an improved fabrication method for C-shaped near-field apertures resonant in the near-IR regime. The apertures are created in a metal layer on a silicon nitride membrane using a focused ion beam and a through membrane milling technique that avoids two problems with fabricating very small apertures: gallium contamination and edge rounding. Finite-difference time-domain simulations predict a 63x more intense near field with a 2.2x smaller spot versus conventionally milled apertures. We verify the position of the simulated resonance peaks with experimental far-field transmission measurements where we also find an increase of 8.8x in intensity. Our method has applications to many other plasmonic devices including bow-tie and fractal apertures, periodic arrays, and gratings.
authors.affiliation: Department of Applied Physics, Stanford University, 420 via Palou Mall, Stanford, California 94305, USA. bleen@stanford.edu
authors.forename: J Brian
authors.initials: JB
authors.lastname: Leen
authors.forename: Paul
authors.initials: P
authors.lastname: Hansen
authors.forename: Yao-Te
authors.initials: YT
authors.lastname: Cheng
authors.forename: Lambertus
authors.initials: L
authors.lastname: Hesselink
mesh_terms: D004867:Equipment Design; D019544:Equipment Failure Analysis; D007477:Ions; D007909:Lenses; D008027:Light; D008422:Materials Testing; D008567:Membranes, Artificial; D012031:Refractometry / Q000295:instrumentation* / Q000379:methods; D012542:Scattering, Radiation; D017655:Silicon Compounds / Q000737:chemistry*; D020349:Surface Plasmon Resonance / Q000295:instrumentation*
chemical_list: D007477:Ions; D008567:Membranes, Artificial; D017655:Silicon Compounds; C032734:silicon nitride