Optimized Growth of Tetra-Needlelike ZnO Whiskers in the Atmosphere for Field-Emission Digital Tube Application

Tetra-needlelike ZnO (T-ZnO) whiskers were directly synthesized by thermal oxidation in the atmosphere. The issue of large variations in morphology, purity, and field-emission performance was found to be greatly relieved through the optimization of the growth temperature, to balance the effects of increasing saturated vapor pressure (P
_s
) of zinc and decreasing oxygen content (n
_O2
) with increasing temperature. The T-ZnO whiskers grown at 1000 °C exhibited uniform morphology, a low turn-ON electric field of 3.2 V/μm , a large field enhancement factor of 7122, and better field-emission stability than whiskers grown at other temperatures, so as to be suitable for application as field emitters. Using the optimized growth process, we fabricated a seven-segment field-emission digital tube which dynamically displayed the numbers 0-9 under the control of a driving circuit.