Tomorrow's light-emitting diodes will be made from smaller, cheaper and more-efficient zinc oxide materials rather than the exotic mixes of gallium, arsenide, indium and nitride used today. That's the vision of electrical engineers at the University of California, San Diego, who recently announced the world's first p-type zinc oxide nanowires. Until now, zinc oxide has been widely used as an n-type piezoelectric material, which can be fabricated into films or nanowires. But only a few labs have been able to formulate a p-type film from zinc oxide, and none had successfully formulated a p-type nanowire. Wang's group created a p-type nanowire by carefully doping zinc oxide nanowires with phosphorus using standard chemical-vapor deposition techniques. The result is a source of holes, which holds the possibility of being juxtaposed with an n-type zinc-oxide nanowire to create a smaller, cheaper and more highly efficient LED.