Structural, optical, and electrical properties of Schottky diodes based on undoped and cobalt-doped ZnO nanorods prepared by RF-magnetron sputtering

Cobalt-doped ZnO nanorods were successfully synthesized on Si/SiO2 substrate using RF-magnetron sputtering at room temperature. The undoped and Co-doped ZnO nanostructures were characterized by XRD, FE-SEM, AFM, and PL spectra. The results showed that Co2+ replaced Zn2+ in the ZnO lattice without changing the wurtzite structure. The ZnO structure became high crystallite and was gradually converted into nanorods without extra phases as increased cobalt doping levels to 3 at.% and 4 at.%. The as-synthesized nanorod arrays were dense and vertically grew on the substrate with lengths of approximately 341 and 382.3 nm for 3 at.% and 4 at.% CO, respectively. PL analysis revealed that the ultraviolet (UV) emission intensity decreased and exhibited a blue shift with increased Co atomic percentage. This result was consistent with the energy bandgap values (3.26-3.3 eV) obtained from UV-vis spectra. The I-V characteristics revealed that the Shottky diodes based on Co-doped ZnO nanostructure with Pd electrodes have high barrier height (0.715-0.797 eV) and low saturation current (0.035-0.841 mu A). The barrier height decreased after annealing the diodes at 500 degrees C for 2 h. To the best of our knowledge, Schottky diodes based on Co-doped ZnO nanorods prepared by RF-magnetron sputtering have not yet been reported. (c) 2013 Elsevier B.V. All rights reserved.