Enhanced structural and photoluminescence properties on GLAD synthesized annealed vertically aligned NiO nanowires

In this study, using glancing angle deposition through electron-beam evaporation, a well-aligned vertical nickel oxide (NiO) nanowire (NW) on Si substrates was fabricated at room temperature. The as-deposited sample was annealed at 500 degrees C for 1hr in open-air conditions. An increase in average crystallite size from 14.44 nm to 21.54 nm with a decrease in lattice strain and dislocation density after annealing was observed. The increase in particle size after annealing as well as the vertically aligned structure of the NWs was confirmed by Top-view and crosssectional FESEM images respectively. Also, the average diameter of the NWs was increased from 27 to 32 nm after annealing. The lattice spacing of 0.144 nm which corresponds to 440 planes (as-deposited sample) and 0.144 nm and 0.205 nm corresponds to 440 and 400 planes (annealed sample) obtained from the HRTEM image is in good agreement with the XRD results. Further, the photoluminescence emission of the sample showed defect-related transitions of the NW which decreased after annealing. The intense emission at the UV region around -355 nm (3.49 eV) arose from the excitonic recombination while deep trap levels were responsible for the emission peaks at the visible region at -402 nm (3.08 eV), -435 nm (2.85 eV) and -465 nm (2.66 eV). The emission peaks were found to broaden after annealing due to lower defects. Thus, the above studies demonstrated the potentiality of NiO NW as a potential material for optoelectronic device applications.