Through the use of some fairly common elements, researchers from North Carolina University believe they’ve solved one of the longer-standing material science problems; that is, how to create semiconductor-based technologies using zinc-oxide.
Zinc oxide powder (via rawelementsusa.com)
A wide range of devices stand to benefit from this discovery, including ultraviolet lasers, LED devices for use in sensors and water treatment, ferromagnetic devices, and more.
Why zinc-oxide?
Laser and LED technologies require the use of “n-type” and “p-type” materials. For those unfamiliar with this science, n-type materials contain an abundance of electrons while p-type materials contain holes that attract these electrons. When electrons pass through these holes, they shed excess energy in the form of photons, or light.
The point at which this occurs is referred to as the “p-n junction” and it’s responsible for producing light used in lasers, LED devices, and more.
For a while now, researchers have wanted to use zinc-oxide for the purpose of providing p-type materials for two reasons: when an electron pass through one of its holes, it doesn’t just produce light, it produces ultraviolet light, and it can be used to make technologies with fewer defects than current UV emitters.
What was the problem with zinc-oxide and how did they solve it?
The problem researchers have had in the past is ZnO material could not consistently produce stable p-type materials. To get around this headache, the NC State research group introduced a “defect complex” via a special set of growth and annealing procedures in the ZnO.
The defect complex itself looks much different from the other normal ZnO molecules; specifically, the zinc atom is absent and a nitrogen atom is substituted for the oxygen atom.
This new solution, if you will, was dispersed all throughout the ZnO, which allowed the material to provide stable “holes” for accepting the electrons. The result — a technology that, even when operated at room temperature, displays remarkable efficiency, and can produce ultraviolet light at the p-n junction.
“The challenge of using ZnO to make these devices has stumped researchers for a long time, and we’ve developed a solution that uses some very common elements: nitrogen, hydrogen and oxygen,” says Dr. Lew Reynolds, co-author of a paper describing the research and a teaching associate professor of materials science and engineering at NC State.
“We’ve shown that it can be done, and how it can be done — and that opens the door to a suite of new UV laser and LED technologies,” says Dr. Judith Reynolds, a research scientist at NC State and lead author of the paper.
Learn more
The group published a paper on their discovery entitled “Shallow acceptor complexes in p-type ZnO” in the journal Applied Physics Letters . It is available for purchase.
Story via: ncsu.edu
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