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 synthesized using RF-magnetron sputtering.
• The nanorod arrays are vertically grow on the SiO2 substrate with length of 382.3 nm.
• The Shotteky diode of undoped ZnO nanostructure has barrier height of 0.85 eV.
• The barrier height decreases after annealing at 500 °C for 2 h to achieve 0.82 eV.
• The annealing step enhanced the ideality factor and reduced the saturation current.

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 μA). The barrier height decreased after annealing the diodes at 500 °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.

Figure optionsDownload as PowerPoint slide