Glowing Nanowires

Photo: Gallium nitride wires growing on a silicon substrate (credit: Lorelle Mansfield/NIST )

Scientists at National Institute of Standards and Technology (NIST) has grown a variety of nanowires and extensively characterized their structural and optical properties and studied defects, strains or impurities, which resulted in high light output compared to the bulk material. NIST is one of few laboratories capable of growing semiconductor nanowires without using metal catalysts. This approach is believed to enhance luminescence and flexibility in crystal design.

A group of researchers at NIST are engaged in growing nanowires made of gallium nitride alloys under high vacuum by depositing atoms layer by layer on a silicon crystal. The wires are generally between 30 and 500 nanometers (nm) in diameter and up to 12 micrometers long. When excited with a laser or electric current, the wires emit an intense glow in the ultraviolet or visible parts of the spectrum, depending on the alloy composition.

A paper in the May 22 issue of Applied Physics Letters reports that individual nanowires grown at NIST produce sufficiently intense light to enable reliable room-temperature measurements of their important characteristics. This will have significant imapct in the world of nanotechnology. Such nanowires can be used to make prototype lasers and light-emitting diodes with emission apertures roughly 100 nm in diameter—about 50 times narrower than conventional counterparts. Nanolight sources may have many applications, including “lab on a chip” devices for identifying chemicals and biological agents, scanning-probe microscope tips for imaging objects smaller than is currently possible, or ultra-precise tools (like sensors and nanoscale mechanical resonators) for laser surgery and electronics manufacturing.

For further details, you may go through the paper we are talking about: J.B. Schlager, N.A. Sanford, K.A. Bertness, J.M. Barker, A. Roshko and P.T. Blanchard. 2006. Polarization-resolved photoluminescence study of individual GaN nanowires grown by catalyst-free MBE. Applied Physics Letters. May 22.