Black metal thin films by deposition on dielectric antireflective moth-eye nanostructures

Alexander Bruun Christiansen, Gideon Peter Caringal, Jeppe Sandvik Clausen, Meir Grajower, Hesham Taha, Uriel Levy, N. Asger Mortensen, Anders Kristensen

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Although metals are commonly shiny and highly reflective, we here show that thin metal films appear black when deposited on a dielectric with antireflective moth-eye nanostructures. The nanostructures were tapered and close-packed, with heights in the range 300-600 nm, and a lateral, spatial frequency in the range 5-7 mu m(-1). A reflectance in the visible spectrum as low as 6%, and an absorbance of 90% was observed for an Al film of 100 nm thickness. Corresponding experiments on a planar film yielded 80% reflectance and 20% absorbance. The observed absorbance enhancement is attributed to a gradient effect causing the metal film to be antireflective, analogous to the mechanism in dielectrics and semiconductors. We find that the investigated nanostructures have too large spatial frequency to facilitate efficient coupling to the otherwise non-radiating surface plasmons. Applications for decoration and displays are discussed.
Original languageEnglish
Article number10563
JournalScientific Reports
Number of pages9
Publication statusPublished - 2015


  • antireflective black silicon
  • black metal thin film
  • dielectric antireflective moth eye nanostructure
  • spatial frequency
  • 10511, Biophysics - Bioengineering
  • semiconductor laboratory equipment
  • Biomaterials


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