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

Abstract

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 (Ps) of zinc and decreasing oxygen content (nO2) with increasing temperature. The T-ZnO whiskers grown at 1000 °C exhibited uniform morphology, a low turn-ON electric field of 3.2 V/ $\mu \text{m}$ , 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.