Synthesis and field emission properties of ZnO nanoneedle arrays grown at low temperatures via a thermal evaporation method

Abstract

We have developed a straightforward and simple strategy for large-scale growth of well-aligned ZnO nanoneedles via a thermal evaporation method. XRD and SAED patterns of nanoneedles can be indexed to hexagonal ZnO with wurtzite structure. Room temperature photoluminescence analysis showed a strong ultra violet emission at 365 nm and a broad deep level visible emission at 472 nm. The growth mechanism of the nanoneedles has been investigated by SEM and the lower pressure of both evaporated zinc and oxygen flux would favor the nucleation of the finer nanowires from those previously formed high coverage spots. The field emission current density of ZnO nanoneedles sharply reached ~0.048 mA/cm2 at a field of 3.1 V/m.