Nano LEDs made easier

Researchers from Samsung Research and Development Center and Kookmin University in Korea have devised a relatively simple method of making arrays of nanoscale light-emitting diodes.

The light-emitting diodes could eventually be used in lasers and in nanoscale lamps used in sensors and microscopes, according to the researchers.

The researchers made a highly ordered array of millions of nano-scale lamps by forming a template of nanoscale holes and filling it with organic semiconductor materials. Each lamp in the moth-eye array is 220 nanometers in diameter, or about twenty-three times smaller than a red blood cell. A nanometer is one millionth of a millimeter.

The researchers' prototypes are made from organic, or plastic materials, but the method could be used to make light-emitting diodes from inorganic materials as well, according to the researchers.

The technique is simpler than previous methods of making nanoscale light-emitting diodes, according to the researchers. To make the diodes the researchers stacked a light-sensitive plastic and a layer of silicon oxide on an indium titanium dioxide wafer. They used a laser beam interference pattern to mark the light-sensitive plastic with 220-nanometer spots spaced 360 nanometers apart. Then they fired beams of ions at the materials to carve tiny holes through the silicon oxide layer at each point a spot appeared. They filled the holes with three types of organic materials, added metal electrodes, and capped the device with a 200-nanometer layer of aluminum.

The researchers' three-by-three-millimeter prototype contains millions of nano-scale lamps.

It will be five to ten years before the nanoscale light-emitting diodes could be ready for practical use, according to the researchers. The work appeared in the March 7, 2005 issue of Optics Express (Nano Hole-Template Organic Light-Emitting Diodes Fabricated Using Laser-Interfering Lithography: Moth-Eye Lighting).