Superabsorbing, artificial metal films constructed from semiconductor nanoantennas

Soo Jin Kim, Junghyun Park, Majid Esfandyarpour, Emanuele F. Pecora, Pieter G. Kik, Mark L. Brongersma

Research output: Contribution to journalArticlepeer-review

30 Citations (Scopus)


In 1934, Wilhelm Woltersdorff demonstrated that the absorption of light in an ultrathin, freestanding film is fundamentally limited to 50%. He concluded that reaching this limit would require a film with a real-valued sheet resistance that is exactly equal to R = η/2 ≈ 188.5Ω/, where η=μ0/ϵ0 is the impedance of free space. This condition can be closely approximated over a wide frequency range in metals that feature a large imaginary relative permittivity ϵr″, that is, a real-valued conductivity σ = ϵ0ϵr″ω. A thin, continuous sheet of semiconductor material does not facilitate such strong absorption as its complex-valued permittivity with both large real and imaginary components preclude effective impedance matching. In this work, we show how a semiconductor metafilm constructed from optically resonant semiconductor nanostructures can be created whose optical response mimics that of a metallic sheet. For this reason, the fundamental absorption limit mentioned above can also be reached with semiconductor materials, opening up new opportunities for the design of ultrathin optoelectronic and light harvesting devices.

Original languageEnglish
Pages (from-to)3801-3808
Number of pages8
JournalNano Letters
Issue number6
Publication statusPublished - 2016 Jun 8
Externally publishedYes


  • Metafilm
  • Mie resonance
  • germanium nanobeam
  • light absorption
  • semiconductor nanoantenna

ASJC Scopus subject areas

  • Bioengineering
  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanical Engineering


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