Growth and conductivity enhancement of N-doped ZnO nanorod arrays

A simple two-step process was developed for growing the nitrogen-doped ZnO (NZO) nanorod arrays on glass substrates. ZnO particles serve as a seed layer deposited by the electrostatic spray deposition method for the growth of NZO nanorods in aqueous solution. FE-SEM images revealed that nanorods have approximately uniform length distribution with hexagon end planes and grow vertically along the c-axis, which was also confirmed by X-rays diffraction. In addition, NZO nanorods had an average diameter of 140±20 nm and an average length of 1.2 to 2.7 μm with a wurtzite-type structure of ZnO. N doping had no prominent effect on the structure and crystal orientation, but it helps to increase the length and reduction in the diameter of nanorods. Moreover, electrical resistivity was found to decrease first and then increase with further nitrogen doping due to the decrease of mobility and increase of carrier concentration. Also the transmittance increased initially, but at higher nitrogen contents it decreased. Annealing the nanorods imparts no effect on the morphology, but there was a significant decrease in electrical resistivity due to the formation of oxygen vacancies. The realization of p-type ZnO nanorod arrays with durable and controlled transport properties is important for the fabrication of nanoscale electronic and optoelectronic devices.

► A simple two-step method was developed for growing the NZO nanorod arrays at low temperature.
► The NZO have almost uniform length distribution and grown vertically along c-axis.
► N doping help to decrease the resistivity due to increase of carrier concentration.
► N doping has no prominent influence on the morphology and structure of ZnO nanorod arrays.
► Electrostatic spray deposited seed layers of ZnO were essential for high quality growth of NZO nanorod arrays.