A new device does the job of both an optical antenna, which collects and focuses light, and a photodiode, which converts light into a current of electrons. This nanoscale device should be useful in photosensing, energy harvesting, imaging and light-detection technologies.
Mark Knight and colleagues grew arrays of gold nano-antennae directly onto a silicon surface. When long-wavelength light hits the antennae, it excites oscillating waves of electrons, known as surface plasmons, which travel near the surface of the metal. These energized electrons then hop the gold-silicon barrier and get trapped in the silicon, where they flow as current.
This research appears in the 06 May 2011 issue of Science.
