Researchers designed experiments allowing them to separate the influence of the metal "wiring" on the motion of electrons and holes from that of the behavior intrinsic to the lead selenide nanowires. By controlling the exposure of the semiconductor nanowire device to oxygen or the chemical hydrazine, they were able to change the conductive properties between p-type and n-type. Altering the duration and concentration of the exposure, the nanowire device type could be flipped back and forth.
"If you expose the surfaces of these structures, which are unique to nanoscale materials, you can make them p-type, you can make them n-type, and you can make them somewhere in between, where it can conduct both electrons and holes," Kagan said. "This is what we call 'ambipolar.'"
Devices combining one n-type and one p-type semiconductor are used in many high-tech applications, ranging from the circuits of everyday electronics, to solar cells and thermoelectrics, which can convert heat into electricity.
"Thinking about how we can build these things and take advantage of the characteristics of nanoscale materials is really what this new understanding allows," Kagan said.
Figuring out the characteristics of nanoscale materials and their behavior in device structures are the first steps in looking forward to their applications.
These lead selenide nanowires are attractive because they may be synthesized by low-cost methods in large quantities.
"Compared to the big machinery you need to make other semiconductor devices, it's significantly cheaper," Kagan said. "It doesn't look much more complicated than the hoods people would recognize from when they had to take chemistry lab."
In addition to the low cost, the manufacturing process for lead selenide nanowires is relatively easy and c
|Contact: Evan Lerner|
University of Pennsylvania