p-type ZnO nanowire arrays

Well-aligned ZnO nanowire (NW) arrays with durable and reproducible p-type conductivity were synthesized on α-sapphire substrates by using N ₂O as a dopant source via vapor-liquid-solid growth. The nitrogen-doped ZnO NWs are single-crystalline and grown predominantly along the [110] direction, in contrast to the [001] direction of undoped ZnO NWs. Electrical transport measurements reveal that the nondoped ZnO NWs exhibit n-type conductivity, whereas the nitrogen-doped ZnO NWs show compensated highly resistive n-type and finally p-type conductivity upon increasing N₂O ratio in the reaction atmosphere. The electrical properties of p-type ZnO NWs are stable and reproducible with a hole concentration of (1-2) × 10 ¹⁸ cm³ and a field-effect mobility of 10-17 cm² V ^-2 s^-1. Surface adsorptions have a significant effect on the transport properties of NWs. Temperature-dependent PL spectra of N-doped ZnO NWs show acceptor-bound-exciton emission, which corroborates the p-type conductivity. The realization of p-type ZnO NWs with durable and controlled transport properties is important for fabrication of nanoscale electronic and optoelectronic devices. © 2008 American Chemical Society.