Peculiarities of electron field emission from ZnO nanocrystals and nanostructured films

ZnO microcrystals and nanocrystals were grown on silicon substrates by condensation from vapour phase. Nanostructured ZnO films were deposited by plasma enhanced metal organic chemical vapour deposition (PEMOCVD). The parameters of field emission, namely form-factor β and work function ϕ, were calculated for ZnO structures by the help of the Fowler-Nordheim equation. The work functions from ZnO nanostructured films were evaluated by a comparison method. The density of emission current from ZnO nanostructures reaches 0.6 mA/cm2 at electric force F=2.1⋅105 V/cm. During repeatable measurements β changes from 5.8⋅104 to 2.3⋅106 cm−1, indicating improvement of field emission. Obtained values of work functions were 3.7±0.37 eV and 2.9-3.2 eV for ZnO nanostructures and ZnO films respectively.