ZnO:Al nanostructures synthesized on pre-deposited aluminum (Al)/Si template: Formation, photoluminescence and electron field emission

Comb-like aluminum (Al) doped ZnO (ZnO:Al) nanostructures were synthesized on Al/silicon substrate by thermal evaporation at 650 °C. A pre-deposited Al layer on the Si substrate was employed to provide the Al dopant into ZnO nanostructures. High-resolution transmission electron microscopy (HRTEM) images displayed that ZnO:Al nanostructures were grown along the [0001] axis. Energy dispersive X-ray spectroscopy (EDS) mapping showed that the Al element was highly scattered and dispersed throughout the ZnO nanostructures. Photoluminescence (PL) spectrum revealed that the ZnO:Al and pure ZnO nanostructures have a blue band emission at 382 nm and 385 nm, respectively. The Al doping did increase the concentration of the oxygen vacancies, therefore a high intensity of green emission band was obtained in ZnO:Al nanostructures as compared to that of pure ZnO nanostructures. The field emission properties of ZnO:Al and ZnO nanostructures were also investigated in this work. The turn-on field of ZnO:Al and pure ZnO nanostructures were found to be 3.8 and 5 V/μm, respectively; the current density was 1 µA/cm2. The thresholds field for ZnO:Al and ZnO nanostructures were estimated around 25 and 47 V/μm, respectively; the current density was 1 mA/cm2.