A University of Pennsylvania research team at the schools of Engineering and Applied Science and Arts and Sciences has discovered a method that will help control the properties of semiconductor nanowires fabricated from lead selenide.
Cherie Kagan, professor in the departments of Electrical and Systems Engineering, Materials Science and Engineering and Chemistry and co-director of Pennergy, Penn's center that concentrates on creating alternative energy technologies, led the team. Semiconductors having nanowires of negative charges that move electrons are n-type. The absence of an electron in p-type is equivalent to relocating a positive charge.
The nanowires need to be wired into a device before being integrated into a circuit. Metal electrodes at both ends permit current to flow in and out. But the wiring could impact the nanowire’s electrical properties, while pollutants could govern the device type. Stringent air-free synthesis, purification and analysis, are used to maintain the cleanliness of the nanowires. This procedure helps identify the lead selenide nanomaterial properties.
The team segregated the metal wiring impact on the electrons and holes movements from that of the lead selenide nanowires. The nanowire device’s exposure to oxygen or chemical hydrazine was controlled to help modify the conductive characteristics between the two types. The device type could be changed back and forth by monitoring the duration and concentration of the nanowires.
Systems that incorporate one of each type are utilized in applications such as electronics circuits, solar cells and thermo electrics, which can turn heat into electricity. The nanowires could be synthesized in large quantities using cost- efficient techniques. The conductivity of the nanowires can be modified within a device allowing them to be used in more applications such as photo sensors.
The research was funded by the National Science Foundation Division of Materials Research, the National Science Foundation Solar Program and the National Science Foundation Nano-Bio Interface Center.