Field emission studies on electrochemically synthesized ZnO nanowires

Nanocrystalline zinc oxide (ZnO) films were synthesized using cathodic reduction of Zn foil in aqueous electrolyte of different molar concentrations containing ZnCl(2) and H(2)O(2), followed by annealing at 400 degrees C in air. An X-ray diffractometer (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM) were used for characterization. The XRD patterns exhibited a set of well-defined diffraction peaks corresponding to the wurtzite phase of ZnO. SEM and TEM images clearly revealed the formation of randomly oriented ZnO nanowires having lengths of several microns and diameters less than 100nm. From the field emission studies, the threshold field values, required to draw emission current density of approximately 1microA/cm(2) were found to be 1.44, 1.36 and 1.5V/mum for nanowires synthesized using 0.002, 0.004 and 0.016M electrolyte concentrations, respectively. All Folwer-Nordheim (F-N) plots showed non-linear behavior indicating semiconducting nature of the emitters. The ZnO nanowires exhibited good emission current stability at the pre-set value of approximately 10microA over a duration of 6h. The simplicity of the synthesis route coupled with the promising emission properties made the electrochemically synthesized ZnO nanowires a suitable candidate for high-current density applications.